Genotype and Population Performances and their Interactions for Growth of Coastal Douglas-Fir in Western Washington - Christine A. Dean (Forest Science, 2007)
The Washington Wide Adaptability study (WWA) is a series of genetic tests established in 1985 across Cascade, Longview, and Twin Harbors regions of western Washington, measured for diameter over-bark at 13 years (dbh13). WWA involves parents of coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) originally selected from wild populations in Cascade, Longview, Twin Harbors, and Vail. Female parents from each population were crossed using pollen-mixes from the same (“intra”) or different (“inter”) populations. Analyses of variance: Female parent (nested within population) accounted for around 2% of total variation in dbh13. Population of the female or male parents accounted for less than 1% variation. The most important genotype × environment (GE) component was female parent (within population) × genetic test (within region), accounting for around 2% variation. Other GE effects accounted for little or no variation. The female source × pollen source (genotype × genotype, GG) effect accounted for only 0.1% of variation in dbh13. Practical implications: GG and GE interactions for dbh13 do not appear sufficiently systematic or large enough to be of practical importance in breeding coastal Douglas-fir across these regions of western Washington, at least for growth to 13 years. It appears possible to select coastal Douglas-fir genotypes that produce strong, stable growth across this range of environments. Movement of improved seed across Cascade, Longview, and Twin Harbors can lead to positive outcomes for plantation productivity at 13 years. There appears little practical benefit in having separate breeding lines of coastal Douglas-fir for these regions. Indeed, strategies of developing local purebred genotypes tested and deployed solely in a local region would most likely deliver suboptimal genetic gain.

Does Monopolistic Competition Explain Intraindustry Trade of Forest Products? - Sijia Zhang; Joseph Buongiorno (Forest Science, 2007)
Intraindustry trade occurs when countries import and export the same product. We found, based on Grubel-Lloyd indices, that there is substantial intraindustry trade of forest products. The explanation of intraindustry trade by the Helpman-Krugman theory of monopolistic competition implies a unit elasticity of exports with respect to production. We studied the existence of such a relationship for 11 forest industries that produce and export roundwood, sawnwood, wood-based panels, wood pulp, and paper and paperboard. The hypothesis was tested with cross-section and time-series data from 43 countries observed from 1961 to 2002. We formulated static and dynamic versions of the relationship between exports and production and estimated them with panel data methods. The best results, based on pattern of the residuals and forecasting errors, were obtained with the static and the dynamic models estimated by ordinary least squares after differencing the time series. The strongest evidence of monopolistic competition was for the pulp and paper industries: newsprint, printing and writing paper, other paper and paperboard, and chemical and semichemical woodpulp. For other forest products, although there was a statistically significant relationship between production and exports, the long-run elasticity was significantly less than unity.

Hedonic Analysis of Hunting Lease Revenue and Landowner Willingness to Provide Fee-Access Hunting - Anwar Hussain; Ian A. Munn; Stephen C. Grado; Ben C. West; W. Daryl Jones; Jeanne Jones (Forest Science, 2007)
Selling hunting access may supplement household income, yet only a small proportion of nonindustrial private (NIP) landowners in United States lease the right to hunt their land. Based on a survey of Mississippi landowners, the decision to lease hunting rights and factors influencing lease revenue per leased hectare were analyzed. The two issues were jointly modeled consistent with Heckman's sample selection model, and the lease revenue was specified in accordance with hedonic pricing theory. Empirical results showed that landowner concerns about loss of privacy, accident liability, and conflicts with personal use of land reduced the likelihood of leasing; total landownership and specific landowner characteristics increased it. With regards to factors explaining differences in lease revenue per leased hectare, bottomland hardwoods commanded a greater premium than many other land uses. In addition, lease revenue per hectare was distinctly higher where a landowner had expertise in managing a hunting lease enterprise. These findings have implications for landowners interested in managing wildlife-associated enterprises and public agencies engaged in the provision of natural resource-based recreation.

Mountain Pine Beetle-Induced Changes to Selected Lodgepole Pine Fuel Complexes within the Intermountain Region - Wesley Green Page; Michael James Jenkins (Forest Science, 2007)
The mountain pine beetle (Dendroctonus ponderosae Hopkins) is a forest insect that infests lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) forests in the Intermountain West. The often widespread mortality caused by the mountain pine beetle has been suggested to result in significant changes to stand structure, composition, and total fuel loading; however, little quantitative information that documents these changes is available. We examined mountain pine beetle–induced changes to ground, surface, and aerial fuels in lodgepole pine stands during current epidemics and 20 years after an epidemic. Results indicated that there were statistically significant increases in the amounts of fine surface fuels in recently infested stands, i.e., those stands ≤5 years past peak mortality. In the previously infested stands, there were large increases in the amounts of dead woody fuels in all but the smallest size classes, with a 7.8-fold increase in down woody fuels ≥7.62 cm in diameter. Live shrubs and the amount of subalpine fir (Abies lasiocarpa Nutt.) regeneration were also significantly greater in the postepidemic stands. The net result of epidemic mountain pine beetle activity was a substantial change in species composition and a highly altered fuels complex in which large dead woody fuels and live surface fuels dominate.

A Maximum Size-Density Relationship between Lorey's Mean Height and Trees per Hectare - Thomas B. Lynch; Robert F. Wittwer; Douglas J. Stevenson; Michael M. Huebschmann (Forest Science, 2007)
A linear relationship between the logarithm of Lorey's mean height and the logarithm of number of trees per hectare at maximum density can be derived from well known maximum size-density relationships associated with Reineke's stand density index and the power self-thinning principle. This leads to a system of three mathematically interrelated maximum size-density equations relating the three classically most important measures of tree size to density at its maximum. Given any two of these three equations, the third can be derived. Data obtained from unthinned control plots in a shortleaf pine (Pinus echinata Mill.) thinning study from Oklahoma are used to demonstrate these relationships. Slope estimates for the Reineke and Lorey maximum size-density lines are fitted simultaneously using three-stage least-squares with parameter constraints. First-difference models were used in the estimation procedure to reduce autocorrelation among remeasured plot data.

Interactions of Elevation, Aspect, and Slope in Models of Forest Species Composition and Productivity - Albert R. Stage; Christian Salas (Forest Science, 2007)
We present a linear model for the interacting effects of elevation, aspect, and slope for use in predicting forest productivity or species composition. The model formulation we propose integrates interactions of these three factors in a mathematical expression representing their combined effect in terms of a cosine function of aspect with a phase shift and amplitude that change with slope and elevation. This model allows the data to determine how the aspect effect changes with elevation and slope. Earlier articles concerning the interactions of slope, aspect, and elevation have been incomplete by either treating elevation as fixed or ignoring the possibility that aspect effect must also involve slope. The proposed set of variables is illustrated in four applications: (1) a hypothetical data set for probability of stocking by “species” having different adaptations to elevation, (2) in a discriminant function for forest/nonforest classification of data from Utah, (3) estimating mean annual increment of Utah forests, and (4) estimating the height asymptote in a mixed-model differential equation predicting Douglas-fir height growth.

Evidence for Increasing Red Maple Abundance in the Eastern United States - Songlin Fei; Kim C. Steiner (Forest Science, 2007)
Red maple (Acer rubrum L.) is widely believed to be increasing in abundance in eastern North America, but most evidence is anecdotal or localized. In this article we present analyses of FIA data sets designed to formally quantify changes in abundance of red maple in the eastern United States during the period of 1980 to 2005. The results indicate that recent increases in red maple abundance are almost ubiquitous on a state-by-state basis throughout the species' natural range and generally greatest in the western portions of the range. No states experienced a significant decrease in red maple abundance during this period. There is evidence that the species has naturalized into areas west of its putative pre-Columbian distribution. Red maple had an inverse “J” population structure, and density of red maple trees has increased in all diameter classes across the region. The trend of increasing red maple abundance will continue unless the circumstances that cause this phenomenon are changed.

Interactive Effects of Soil Temperature and [CO2] on Morphological and Biomass Traits in Seedlings of Four Boreal Tree Species - Shouren Zhang; Qing-Lai Dang (Forest Science, 2007)
To better understand how soil temperature will influence the responses of boreal trees to increasing atmospheric [CO2], one-year-old jack pine (Pinus banksiana lamb.), black spruce (Picea mariana [Mill.] B.S.P.), white spruce (Picea glauca [Moench] Voss), and current-year white birch (Betula paperifera Mash) seedlings were subjected to two [CO2] (360 versus 720 μmol mol−1) and three soil temperatures (T soil = 7, 17, and 27°C initially, increased to 10, 20, and 30°C 3 months later) for 4 months. The low T soil significantly suppressed height growth, stem biomass, and total biomass in white birch, black and white spruce, root collar diameter (RCD), and foliage biomass in white birch and white spruce, as well as root biomass in white birch under both ambient and elevated [CO2] and in white spruce under ambient [CO2]. This low T soil effect was much more significant in white birch than in the conifers. The [CO2] elevation significantly increased RCD, foliar biomass, and total biomass of the four species at all soil temperatures, stem biomass of all the species at the low T soil, and the root biomass of white birch at intermediate T soil. The data suggest that the [CO2] elevation compensated for the negative effects of low T soil, e.g., the low T soil significantly decreased the height and total biomass of black and white spruce at ambient [CO2], but not at elevated [CO2]. The high T soil had much smaller negative effects on growth and biomass than did the low T soil. Jack pine was the least responsive to T soil and [CO2]. In general, the ratios of stem, foliage, and root mass to total mass were much less responsive to the treatments than total or component biomass. Neither treatment significantly affected the volume/mass ratio of the stem in any of the four species. The data suggest that white birch and white spruce will benefit the most and jack pine will benefit the least from the increasing atmospheric [CO2].

Modeling Pulpwood Trade within the United States South - Maksym Polyakov; Lawrence Teeter (Forest Science, 2007)
Interregional trade of roundwood products is an important factor of regional roundwood markets. Until now, regional and subregional forest sector models did not account for the spatial aspects of roundwood markets. This article explores ways to model interregional trade of roundwood products. It compares the performance of different specifications of a gravity model (the model widely used in the analysis of international trade) and a fixed gravity coefficient model (common in regional input-output analysis) to forecast pulpwood trade between the states of the United States South. The gravity model estimated using nonlinear least-squares with fixed effects (NLS FEM) and the fixed gravity coefficient model (FGCM) showed the best results. Another important result of this study is the finding that the fixed gravity coefficients for pulpwood trade in the United States South are temporally stable. This suggests the possibility of using the FGCM for modeling roundwood trade in the absence of time series data.

Trade Liberalization and Land Use Changes: Explaining the Expansion of Afforested Land in Chile - Mario E. Niklitschek (Forest Science, 2007)
Trade policy reforms are expected to affect land use patterns in developing countries. Most of the research has focused on explaining deforestation or the economic and environmental consequences of plantation subsidies. This article examines the change in economic incentives resulting from trade reforms implemented in Chile since the mid-1970s for land conversion to forest plantations. The removal of the log export ban and the general import duties reduction affected forestry and land-competing agriculture both directly and indirectly through the depreciation of the real exchange rate. Counterfactual roundwood relative prices were obtained by estimating a generalized Leontief demand function for the domestic processing industry, and the “omega” coefficient used in the analysis of agricultural trade reforms. The effects on the economic incentives for land conversion were measured as the land rent changes under forestry and under competing agricultural use that resulted from counterfactual policy scenarios. The results show the critical role of trade liberalization policies in creating the necessary economic incentives for the private participation in the expansion of forest plantations in Chile. The direct effect from the removal of the log export ban was estimated to be larger than the indirect effect of the general import duty reductions.

Landscapes, Genomics, and Transgenic Conifers (Forest Science, 2007)

Biodiversity Conservation in Commercial Boreal Forestry: The Optimal Rotation Age and Retention Tree Volume - Erkki Koskela; Markku Ollikainen; Timo Pukkala (Forest Science, 2007)
This article examines biodiversity conservation in commercial boreal forests. The means of promoting biodiversity are green tree retention and prolonged rotation age, which create dead and decaying wood artificially and via natural mortality, respectively. We extend the Hartman model to cover biodiversity benefits and to allow for leaving retention trees standing at the final felling. We first characterize qualitatively the socially optimal choice of the harvest volume and rotation age. We then assess empirically the optimal solution in a simulation model calibrated to the Finnish forestry for a pine stand. We find that biodiversity conservation increases the socially optimal rotation age beyond the Faustmann rotation age. The optimal volume of retention trees increases (decreases) with biodiversity valuation (timber price). The optimal retention volume is higher than suggested by the current forest management recommendations or certification systems.

The Components of Change for an Annual Forest Inventory Design - Francis A. Roesch (Forest Science, 2007)
The sample design of the USDA Forest Service's Forest Inventory and Analysis Program (FIA) with respect to a three-dimensional population (forest area × time) of tree attributes is formally defined and evaluated. The definitions for both the traditional components of growth, as presented by Meyer (1953, Forest Mensuration), and a discrete analog to the time invariant redefinition of the components of change given by Eriksson (1995, Forest Sci. 41(4):796–822), are compared and contrasted. Special problems in the application of the traditional definitions due to the continuous and overlapping temporal intervals featured in the sample design are explored. This exploration supports a contention that the traditional definitions are at a theoretical disadvantage because they are not based purely on the population(s) of interest, while the redefinitions dubbed the components of change by Eriksson (1995) were based solely on population attributes. The temporally discrete analog to the Eriksson definitions are used in this article to define the three-dimensional populations in terms of a set of mutually exclusive component matrices that can be summed to represent the entire population, independently of the sample design.

Productivity of Three Young Mixed-Species Plantations Containing N2-Fixing Acacia and Non-N2-Fixing Eucalyptus and Pinus Trees in Southeastern Australia - David I. Forrester; Jürgen Bauhus; Annette L. Cowie; Peter A. Mitchell; John Brockwell (Forest Science, 2007)
Mixed species plantations have the potential to exceed the biomass production of monocultures. This study examined the productivity of three mixed species plantations in southeastern Australia. Two of these trials contained a Eucalyptus sp. (E. saligna Smith or E. nitens [Deane & Maiden] Maiden) planted with Acacia mearnsii De Wild., and the other contained Pinus radiata D. Don with A. mearnsii, A. decurrens Willd., E. benthamii Maiden & Cambage, or E. smithii R. Baker. Each trial contained both monocultures and mixtures, and was replicated three or four times. Tree diameters or heights were smaller in mixture than monocultures for some species (P. radiata diameters of 5.9 cm and 7.0 cm in 2:1 mixtures with A. mearnsii and monocultures, respectively) but tended to increase (not significantly) for other species (E. nitens diameters of 10.6 cm and 8.5 cm and A. mearnsii diameters of 9.2 cm and 8.8 cm in 1:1 mixtures and monocultures, respectively). As a result, mixtures were intermediate in aboveground biomass production between monocultures of the mixed species in each trial, or they were not significantly different from the monocultures. Competition for resources other than nitrogen (N), such as light, soil moisture, or other nutrients, appeared to balance any positive effects that might have occurred, such as through increased N availability. For example, foliar N concentrations of E. saligna were higher in mixture (23.1 mg g−1) than monoculture (17.7 mg g−1); however, this did not result in greater aboveground tree biomass. The range of different growth responses from mixing different species in this study and in other studies shows that a fundamental understanding of the underlying processes is required to enable a greater predictive capacity of the circumstances under which mixtures can be successful.

Mountain Pine Beetle Dispersal: The Spatial–Temporal Interaction of Infestations - Colin Robertson; Trisalyn A. Nelson; Barry Boots (Forest Science, 2007)
An understanding of mountain pine beetle (Dendroctonus ponderosae Hopkins) dispersal during an outbreak is important for modeling future infestations and aiding management decisions. Data on the spatial pattern of red and green attacked trees were used to characterize the spatial–temporal nature of dispersal. Research goals were to detect evidence of dispersal based on the distance and direction between red and green attacked tree clusters, determine how dispersal changes at different stages of infestation, and to detect landscape variables influencing the observed dispersal patterns. Key variables explored were Biogeoclimatic Ecosystem Classification (BEC), topography, and the local population of susceptible hosts. Dispersal distances of 30 meters and 50 meters were consistently observed among different data subsets. Findings suggest that short-range dispersal often occurs despite an available population of susceptible hosts, and as the infestation grows in intensity, the abundance of dispersing beetles causes spot infestations to coalesce.

Comparison of Methods to Estimate Reineke's Maximum Size-Density Relationship Species Boundary Line Slope - Curtis L. VanderSchaaf; Harold E. Burkhart (Forest Science, 2007)
Maximum size-density relationships (MSDR) provide natural resource managers useful information about the relationship between tree density and average tree size. Obtaining a valid estimate of how maximum tree density changes with changes in average tree size is necessary to describe these biological relationships accurately. This article examines three methods to estimate the slope (b) of the MSDR species boundary line across a range of planting densities: ordinary least-squares (OLS), first-difference model, and the linear mixed-effects model. For this article, stability refers to the extent to which parameter estimates do not change when the range of planting densities in the fitting data set changes. When using data from a planting density trial consisting of planting densities ranging from 6,727 to 747 seedlings per hectare, mixed-effect models produced the most stable estimates of b while OLS resulted in the least stable estimates. MSDR boundaries have been defined as either (1) those that describe the boundaries of individual stands (MSDR dynamic thinning line) or (2) those that describe MSDRs common across all sites for a particular species in a certain geographical region (MSDR species boundary line). A further refinement of the MSDR species boundary line is proposed by defining two MSDR species boundary lines, labeled here as I and II. Although both MSDR species boundary lines are positioned above all observations, one MSDR species boundary line, II, has a slope that can be considered the population average of all MSDR dynamic thinning lines; the other species boundary line (I) has a slope that results from positioning the boundary above all observations without accounting for self-thinning patterns of individual stands. A mixed-effects analysis was used to estimate the slope of MSDR species boundary line II.

Headwater Streams and Timber Harvest: Channel, Macroinvertebrate, and Amphibian Response and Recovery - C. Rhett Jackson; Darold P. Batzer; Sarah S. Cross; Stephanie M. Haggerty; Christopher A. Sturm (Forest Science, 2007)
Abiotic and biotic responses of 15 first-order streams to timber harvest were monitored at four sites in Washington's Coast Ranges (six watersheds clearcut to streambanks; four clearcut with stream buffers; and four references). Surveys of geomorphology, macroinvertebrates, and amphibians were conducted in 1998 (baseline), 1999 (immediately postharvest), 2000 (macroinvertebrates only) and 2001. Logging slash immediately covered or buried clearcut channels with 0.5 to 2 meters of slash, increasing roughness and trapping fine sediments, and slash still dominated channel conditions in 2001 when fine sediment fractions remained elevated relative to reference streams. In buffered and reference streams, particle size distributions were almost unchanged. Buffer blowdown was extensive (33% to 64%); increased light stimulated streamside vegetation. In 1999, clearcut streams supported higher macroinvertebrate densities of collectors and shredders, likely due to increased detrital resources. Collector response persisted into 2001, and new responses included higher overall macroinvertebrate biomass in buffered streams. No macroinvertebrate groups declined significantly in the three summers after harvest. Clearcutting to stream channels appeared to have short-term negative effects on local giant salamander and tailed frog populations but not torrent salamanders.

Vertebrate Assemblages Associated with Headwater Hydrology in Western Oregon Managed Forests - Deanna H. Olson; George Weaver (Forest Science, 2007)
We characterized headwater stream habitats, fish and amphibian fauna, in and along 106 headwater stream reaches at 12 study sites within managed forest stands 40 to 70 years old in western Oregon. Headwater stream types in our sample included perennial, spatially intermittent, and dry reaches. We captured 454 fish of three species groups and 1,796 amphibians of 12 species. Using canonical correlation, nonmetric multidimensional scaling ordination, and generalized linear models, we identified species and assemblages associated with reach hydrologic type (e.g., perennial, intermittent, dry), stream size, gradient, and substrate composition. Our findings of torrent salamander (Rhyacotriton species) occurrences in spatially intermittent streams, and patchy and infrequent occurrences of Cottus fish (sculpins) and coastal tailed frogs (Ascaphus truei Stejneger) suggests these taxa warrant consideration during headwater management for retention of locally distinct biotic resources.

Preliminary Study of the Effects of Headwater Riparian Reserves with Upslope Thinning on Stream Habitats and Amphibians in Western Oregon - Deanna H. Olson; Cynthia Rugger (Forest Science, 2007)
We conducted a preliminary examination of the responses of stream amphibians and instream habitat conditions to alternative riparian buffer zones with forest thinning upslope. Pre and posttreatment surveys were carried out on 68 headwater stream reaches (including 23 unthinned reference reaches) at 11 sites in western Oregon. Streams were in managed conifer stands, 40 to 80 years old, where the thinning treatment reduced stands from 600 trees per hectare (tph) to 200 tph. Treatments consisted of four widths of riparian buffers approximately 6, 15, 70, and 145 m on each side of streams. Over three study years, 3,131 individuals of 13 species were detected. For the more common instream and bank species analyzed, capture rates persisted posttreatment with no negative treatment effect from thinning with any of the buffer widths. More animals were detected after thinning in treatment reaches compared to reference reaches for rough-skinned newts (Taricha granulosa Skilton) occurring on stream banks, and for instream coastal giant salamanders (Dicamptodon tenebrosus Baird and Girard). Treatment effects on instream habitat parameters were not detected. Interannual variation was evident for western red-backed salamanders (Plethodon vehiculum Cooper), and several habitat conditions including pool-riffle ratio, stream spatial intermittency, stream width, and down wood. Overall, riparian buffers with moderate upslope thinning (200 tph) seemed to have retained the aquatic vertebrate community along channels among sites in the first 2 years posttreatment; however, several limitations of the study reduce the inference of the findings, and these preliminary results are best interpreted as hypotheses for further investigation.

Influence of Headwater Site Conditions and Riparian Buffers on Terrestrial Salamander Response to Forest Thinning - David E. Rundio; Deanna H. Olson (Forest Science, 2007)
Although thinning of young, even-aged forests may accelerate the development of characteristics associated with mature forests, in the short term it may negatively affect some taxa, including terrestrial salamanders. Preexisting site conditions, including down wood, and forest management measures, such as riparian buffers, may moderate these effects, but these relationships are poorly understood. To explore whether down wood and riparian buffer widths might influence short-term responses to thinning, we sampled salamanders using ground searches before and during the first 2 years after experimental thinning at two 45- to 65-year-old headwater forest sites in western Oregon that differed in down wood volume. Prethinning distributions of terrestrial salamanders overlapped one- and two-tree height riparian buffers, and except for red-backed salamanders, overlapped very little with narrower streamside or variable-width buffers. At the site where down wood volume was low, captures of ensatina (Ensatina eschscholtzii Gray) and western red-backed salamanders (Plethodon vehiculum Cooper) both declined by 40% in thinned areas. In contrast, captures of ensatina and Oregon slender salamanders (Batrachoseps wrighti Bishop) were not significantly affected by thinning at the site where down wood volume was high. Our results suggest that site conditions, such as down wood volume, and riparian buffers may influence the effect of thinning on terrestrial salamanders, and demonstrate the tight linkage among management of aquatic, riparian, and upslope resources in headwater forests.

Effects of Clearcutting and Riparian Buffers on the Yield of Adult Aquatic Macroinvertebrates from Headwater Streams - Andrew R. Moldenke; Carolyn Ver Linden (Forest Science, 2007)
We studied the emergence of Ephemeroptera, Plecoptera and Trichoptera (EPT) from headwater streams in Pacific Northwest conifer forests with emergence traps. We analyzed the effects of silvicultural management (clearcutting and riparian buffering) on insect species assemblages as a measure of the quantity of food resource available to insectivorous predators. Canopy removal increased the biomass and density of total EPTs and all feeding guilds except scrapers. Buffering does not change EPT yield from that of the mature forest (perhaps it decreases it), but the EPT community composition within the buffers becomes similar to that of adjacent clearcuts. Differences in community composition attributed to changes in elevation were more substantial than differences caused by silvicultural management. Forty percent of the species collected were restricted to one or another of the five sites.

Stream Macroinvertebrate Community Responses as Legacies of Forest Harvest at the H.J. Andrews Experimental Forest, Oregon - Charles Frady; Sherri Johnson; Judy Li (Forest Science, 2007)
To evaluate long-term effects of forest harvest, we sampled benthic and emergent macroinvertebrate communities in headwater streams through young-growth and old-growth forests in the H.J. Andrews Experimental Forest, Oregon, from June, 2003 to June, 2004. Thirty to forty years after harvest, macroinvertebrate density and richness did not differ among streams through young growth and old growth. Effects of deciduous riparian vegetation, including seasonal canopy openings and litterfall, continue to influence patterns of macroinvertebrate responses to forest harvest, as shown by higher densities of shredders in young-growth sites, the timing of emergence within basin pairs, and assemblage differences in two of the pairs of basins. The paired-basin design helped in distinguishing the specific influences of forest age from natural variability of macroinvertebrate distributions within the 5th order Lookout Creek basin. Our study suggests that understanding how macroinvertebrates respond to historical disturbances is enhanced by measures sensitive to changes in life history, such as rates of emergence, and to functional composition that reflect resource availability.

Headwater Riparian Microclimate Patterns under Alternative Forest Management Treatments - Jessica J. Rykken; Samuel S. Chan; Andrew R. Moldenke (Forest Science, 2007)
Management of headwater streams and their riparian zones has included the implementation of forested riparian buffers, which are intended to protect ecological processes (such as microclimate) and biota, but the appropriate widths for these buffers have been widely debated. We measured the magnitude and extent of microclimatic gradients associated with headwater streams in mature unmanaged forests, and determined whether these patterns were maintained in clearcut harvested units with and without a 30 m-wide riparian buffer on each side of the stream. We measured air temperature, soil temperature, and relative humidity between 1 and 70 m from the stream in five replicate blocks of three treatments each in western Oregon. Results indicated the strongest stream effect on air temperature and relative humidity to be within 10 m of the stream in all management treatments at 3:00 pm, and gradients were evident to 20 m in the forested treatment. The clearcut was significantly hotter (air and soil) and drier than either the riparian buffer or the forest treatments at 3:00 pm. The riparian buffer and forest had similar microclimates at all distances from the stream, suggesting that the 30-m buffer adequately protected the riparian microclimatic gradient. We hypothesize that the strong stream effect on microclimate in the riparian zone serves a critical role in mitigating the influence of microclimatic “edge effects” associated with the forest-clearcut edge. Biota dependent on cool, humid microclimates provided by riparian zones will benefit from the implementation of riparian buffers in harvest units.

On Debris Flows, River Networks, and the Spatial Structure of Channel Morphology - Paul E. Bigelow; Lee E. Benda; Daniel J. Miller; Kelly M. Burnett (Forest Science, 2007)
We evaluated the morphological effects of debris flows from headwater streams in larger, fish-bearing channels of the central Oregon Coast Range, including their influence on fans, wood recruitment, and channel morphology. Continuous channel surveys (6.4 km) were conducted in third- through fifth-order streams (drainage area <10 km2 and slope <7%) where debris fan effects at confluences were most evident. This basin size contains the majority of channels (67%) in the central Coast Range with gradients that are used by coho salmon (Oncorhynchus kisutch Walbaum). The close spacing between headwater tributaries susceptible to debris flows (118 m average) resulted in long continuous sections of fish-bearing streams that were bordered by debris fans (103 m average) and debris fans impinging on 54% of the total channel length surveyed. Debris flows also supplied the majority of wood (58% of pieces) to the surveyed fish-bearing channels. The highest values of large wood, boulders, and channel gradients were associated with debris fans at confluences with headwater tributaries, while deeper sediment deposits were often associated with fans but also extended up and downstream from fans. The spacing and network pattern of debris flow-prone headwater tributaries influenced the spatial structure of channel morphology and aquatic habitats leading to a high degree of physical heterogeneity and patchiness in channel environments. Our study contributes to a growing emphasis on the role of tributary confluences in structuring channel morphology and aquatic habitats in mountain drainage basins and argues for including a confluence component to stream classification and habitat typing schemes.

NetMap: A New Tool in Support of Watershed Science and Resource Management - Lee Benda; Daniel Miller; Kevin Andras; Paul Bigelow; Gordon Reeves; David Michael (Forest Science, 2007)
An integrated suite of numerical models and analysis tools (NetMap) is created for three purposes: (1) Develop regional scale terrain databases in support of watershed science and resource management, (2) Automate numerous kinds of watershed analyses keying on environmental variability for diversifying resource management options, and (3) Improve tools and skills for interpreting watershed-level controls on aquatic systems, including natural disturbance. Hillslope attributes, such as erosion potential, sediment supply, road density, forest age, and fire risk are aggregated down to the channel habitat scale (20–200 m) allowing unique overlap analyses, and they are accumulated downstream in networks revealing patterns across multiple scales. Watershed attributes are aggregated up to subbasin scales (10,000 ha), allowing comparative analyses across large watersheds and landscapes. Approximately 25 automated tools address erosion risk, habitat indices, channel classification, habitat core areas, habitat diversity, and sediment and wood supply, among others. Search functions target overlaps between specific hillslope and channel conditions and between roads and landslide or debris flow potential. To facilitate its use, NetMap contains hyperlinked users' manuals and reference materials, including a library of 50 watershed parameters. NetMap provides decision support for forestry, restoration, monitoring, conservation, and regulation.

Effects of Timber Harvest on Suspended Sediment Loads in Mica Creek, Idaho - Diana L. Karwan; John A. Gravelle; Jason A. Hubbart (Forest Science, 2007)
Long-standing concerns exist regarding timber harvest and subsequent sediment impacts on aquatic resources. Intensive studies on contemporary harvest practices remain rare, particularly in the interior Pacific Northwest. To investigate this, a network of seven automated stream monitoring flumes was installed in the Mica Creek Experimental Watershed, in northern Idaho. Beginning in 1991, water samples collected at each flume under both flow-based and stream-stage storm rise conditions have been analyzed for total suspended solids (TSS). This period of record encompasses a pretreatment time interval from 1991 to 1997, and two treatment time intervals: post-road from 1998 to 2001 and post-road/post-harvest from 2001 through 2004. Treated and control catchments were statistically compared using a paired watershed approach for immediate and recovery time intervals corresponding to each treatment activity, road construction and timber harvest. The impacts corresponding to road construction remain difficult to discern. The impacts corresponding to timber harvest differ based on harvest treatment and time period of analysis. Results suggest a correlation between increased sediment loads and clearcutting for a brief period following the harvest. No significant correlation was found in the partial cut watershed. Continued monitoring at these sites is planned to evaluate trends over subsequent years.

Timber Harvest Impacts on Water Yield in the Continental/Maritime Hydroclimatic Region of the United States - Jason A. Hubbart; Timothy E. Link; John A. Gravelle; William J. Elliot (Forest Science, 2007)
The inland Pacific Northwest of the United States is influenced by both maritime and continental hydrometeorogical conditions. To date there are limited studies of hydrologic impacts resulting from contemporary timber harvest in this region. Streamflow data were collected since 1991 at the Mica Creek Experimental Watershed (MCEW) in northern Idaho. Treatments were designed to isolate the effects of road construction and two different harvest practices (50% clearcut, 50% partial cut). The change in water yield was assessed using linear regression and analysis of covariance (ANCOVA). Water yield increased in excess of 270 mm/yr (P < 0.01) after clearcut harvesting, and by more than 140 mm/yr (P < 0.01) after partial cut harvesting. Monthly and seasonal analyses revealed the largest impacts of harvest practices on water yield during the snow deposition and melt season from November through June. Dry season analyses (July through October) indicated negligible water yield increases after treatments. Estimates of evapotranspiration (ET) as the residual of the catchment water balance suggest that ET was reduced by 35% and 14% after clearcut and partial cut harvest, respectively. These results establish a base on which to develop tools for effective watershed management in the northern Idaho continental/maritime hydroclimatic region.

Sediment and Wood Routing in Steep Headwater Streams: An Overview of Geomorphic Processes and their Topographic Signatures - Christine May (Forest Science, 2007)
Headwater streams in steep terrain pose a significant challenge for the development of best management practices (BMP) in forested watersheds. There is an incomplete understanding of the processes that govern the input, storage, and transport of sediment and wood, and these processes differ geographically. At the upstream extent of the channel network, headwater streams represent a transition from hillslope to channel processes. At the downstream extent, many of these channels transition from mass wasting to fluvial process dominance. Large-scale sediment routing processes typically consist of debris flows, earth flows, and/or gully erosion. In the interval between episodic transport events, headwater streams can interrupt the delivery of sediment from hillslopes to larger river systems by storing large volumes of sediment and wood. Forest management guidelines typically identify headwater streams as occurring upstream of the distribution of fish; however, a topographically based designation of headwater streams could prove useful for identifying which erosional processes are dominant in a particular area. Broad-scale terrain analysis based on unique topographic signatures can be used to identify the spatial domain of different geomorphic landforms that govern headwater stream processes, how they may be affected by forest management, and to infer the type and severity of downstream disturbance.

Introduction to Special Issue on Headwater Streams - Robert J. Danehy; George G. Ice (Forest Science, 2007)

Periphyton and Macroinvertebrate Assemblage Structure in Headwaters Bordered by Mature, Thinned, and Clearcut Douglas-Fir Stands - Robert J. Danehy; Samuel S. Chan; Gary T. Lester; Russell B. Langshaw; Ted R. Turner (Forest Science, 2007)
We examined the structure of periphyton and macroinvertebrate assemblages in 18 Oregon Coast Range perennial headwater streams bordered by mature (6), clearcut (5), and thinned (7) forest treatments. Summer base flow discharge ranged from 0.02 to1.98 l/s (mean − 0.5 l/s). Periphyton was almost entirely diatoms (72 species) and assemblage characteristics were most strongly influenced by substrate characteristics. Mature treatment sites had fewer species of diatoms and less biomass than other treatments. Diatom richness was highest at sites with higher unit area discharge. Diatom assemblages were dominated by a single species (Achnanthes lanceolata [Brébisson] Grunow), which composed more than 50% relative abundance of the assemblage at nine sites. Macroinvertebrate assemblages were rich, with 194 taxa collected across all sites and 42 taxa found at a single site. Macroinvertebrate assemblages differed across treatments with higher abundance, more Chironomidae taxa, and more biomass at the clearcut treatment sites. We observed no difference in functional feeding group percentage composition across treatments, with collector-gatherers and shredders composing at least 50% abundance at all treatments. We found little difference in either periphyton or macroinvertebrate assemblages between thinned and mature treatments.

Riparian Buffer and Density Management Influences on Microclimate of Young Headwater Forests of Western Oregon - Paul D. Anderson; David J. Larson; Samuel S. Chan (Forest Science, 2007)
Thinning of 30- to 70-year-old Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands is a common silvicultural activity on federal forest lands of the Pacific Northwest, United States. Empirical relationships among riparian functions, silvicultural treatments, and different riparian buffer widths are not well documented for small headwater streams. We investigated buffer width and density management effects on riparian microclimates of headwater streams in western Oregon. Spatial variations in stand density, canopy cover, and microclimate were measured along transects extending from stream center upslope into thinned stands, patch openings, or unthinned stands, with riparian buffers ranging from <5 m up to 150 m width. For treated stands, summer mean daily air and soil temperature maxima increased, and mean daily humidity minima decreased with distance from stream. Microclimate gradients were strongest within 10 m of stream center, a distinct area of stream influence within broader riparian areas. Thinning resulted in subtle changes in microclimate as mean air temperature maxima were 1 to 4°C higher than in unthinned stands. With buffers 15 m or greater width, daily maximum air temperature above stream center was less than 1°C greater, and daily minimum relative humidity was less than 5% lower than for unthinned stands. In contrast, air temperatures were significantly warmer within patch openings (+6 to +9°C), and within buffers adjacent to patch openings (+3°C) than within unthinned stands. Buffers of widths defined by the transition from riparian to upland vegetation or topographic slope breaks appear sufficient to mitigate the impacts of upslope thinning on the microclimate above headwater streams.

Streamside Policies for Headwater Channels: An Example Considering Debris Flows in the Oregon Coastal Province - Kelly M. Burnett; Daniel J. Miller (Forest Science, 2007)
Management policies are increasingly debated for headwater channels given their prevalence and ecological importance in many landscapes. Quantitative differences among headwater channels may offer an objective basis for prioritizing streamside protection. Here, we examine differences among headwater channels as potential transport corridors for debris flows. Specifically, we model differences among hill slopes and headwater channels in probabilities of initiating and being traversed by debris flows that deliver to fish-bearing channels. We develop an approach to rank these probabilities and apply the ranks in delineating alternative streamside management zones. Initiation and traversal probabilities are estimated from an empirically calibrated debris-flow model using regionally available 10-m digital elevation data. Alternatives are delineated by encompassing 25%, 50%, and 75% of debris-flow susceptible hill slopes and headwater channels. Highest initiation and traversal probabilities were contained in a relatively small percentage of the study area. Encompassing lower probabilities required disproportionately larger areas. Substituting delineated alternatives for currently prescribed headwater riparian management zones decreased the total area encompassed on federal lands but increased it on private and state lands. Our intent is not to advocate for any particular alternative but to demonstrate that knowledge about how headwater channels differ over large areas can help tailor riparian policies.

Influence of Timber Harvesting on Headwater Peak Stream Temperatures in a Northern Idaho Watershed - J.A. Gravelle; T.E. Link (Forest Science, 2007)
Concerns regarding the impacts of contemporary timber harvest practices on stream water temperature emphasize the need for improved understanding of temperature patterns and changes related to disturbances in headwater catchments. A network of water temperature recorders was installed in the Mica Creek Experimental Watershed in northern Idaho to investigate the relationships among forest treatments, stream temperatures, and riparian cover. Sensors were placed in first-order, nonfish-bearing unimpacted reaches, nonfish-bearing harvested reaches, and downstream into second- and third-order fish-bearing reaches of the stream network. Treated watersheds consisted of 50% canopy removal by contemporary clearcut methods and selective cut practices. Riparian canopy cover in the first-order reaches was measured during the pretreatment and posttreatment periods with a spherical densiometer. Despite estimated increases of up to 3.6°C in the directly impacted nonfish-bearing reaches, there was no significant increase in water temperature maxima at the downstream fish-bearing sites. Results also demonstrate that water temperatures in headwater stream networks can be highly variable and that the potential shade value of understory vegetation in harvested areas should not be overlooked. Continued monitoring at these sites is planned to evaluate peak water temperature trends during canopy regrowth and hydrologic recovery.

Structures Linking Physical and Biological Processes in Headwater Streams of the Maybeso Watershed, Southeast Alaska - Mason D. Bryant; Takashi Gomi; Jack J. Piccolo (Forest Science, 2007)
We focus on headwater streams originating in the mountainous terrain of northern temperate rain forests. These streams rapidly descend from gradients greater than 20% to less than 5% in U-shaped glacial valleys. We use a set of studies on headwater streams in southeast Alaska to define headwater stream catchments, link physical and biological processes, and describe their significance within watersheds. We separate headwater stream systems into four units that have distinct hydrologic and geomorphic processes that link terrestrial processes to aquatic systems. Headwater streams collect, process, and transport material downstream. Physical and biological processes in headwater streams are complex and closely tied to terrestrial processes. Steps and step pools formed by large wood are keystone structures that link physical processes to biological processes and increase channel complexity. Large and coarse wood debris dams form in-channel step structures and act as valves that regulate the downstream flow of material. A large amount of inorganic and organic sediment is stored in step structures, which may be biological hotspots in headwater streams. Step pools formed by large woody debris are critical habitat for Dolly Varden (Salvelinus malma), juvenile coho salmon (Oncorhynchus kisutch), steelhead (O. mykiss), and cutthroat trout (O. clarkii) in reaches with gradients from less than 4% to those greater than 10%. Landslides and debris flows are the dominant channel-altering processes in headwater streams and remove the step profile. Management activities that increase the number and frequency of channel disturbance events in headwater streams can have important and long-term consequences throughout a watershed.

Influence of Headwater Streams on Downstream Reaches in Forested Areas - Lee H. MacDonald; Drew Coe (Forest Science, 2007)
The source areas of headwater streams typically compose 60% to 80% of a catchment. This, plus the typical increase in precipitation with elevation, means that headwater streams generate most of the streamflow in downstream areas. Headwater streams also provide other important constituents to downstream reaches, including coarse and fine sediment, large woody debris, coarse and fine organic matter, and nutrients. The relative importance of headwater streams as a source of these other constituents is highly variable because the amount and quality of each constituent can be modified by in-channel storage, dilution, biological uptake, diminution, and chemical transformations. Headwater sources of water, fine sediment, and fine particulate organic matter are more likely to be delivered to downstream reaches than coarse sediment, woody debris, nutrients, or an increase in water temperatures. The complexity and temporal variability of channel-hillslope interactions, in-channel processes, and downstream conditions makes it difficult to rigorously link upstream inputs and anthropogenic activities to the condition of downstream resources. These issues may preclude the use of adaptive management, particularly in larger basins, as adaptive management implicitly assumes that (1) downstream changes can rapidly be detected, (2) management will change rapidly in response to any adverse change, and (3) a management change will rapidly improve the affected resource. Since these assumptions may be difficult to satisfy—particularly in larger basins—the use of adaptive management must be carefully examined before it can be applied at the watershed scale.

Policy and Management for Headwater Streams in the Pacific Northwest: Synthesis and Reflection - Paul W. Adams (Forest Science, 2007)
The primary policy and management concern for headwater streams in the Pacific Northwest has been their potential influence on downstream water quality and fish habitat; and on federal lands, riparian wildlife habitat also has been a significant consideration. Regulations have been the primary policy tool used by state and federal agencies in the region to promote desired management for these areas, and to comply with federal laws for water quality and species protection. Management directives initially were relatively minor for headwater areas, but in recent years increased science assessments, research, and legal issues resulted in some notable policy proposals and changes for public and private lands. These measures focus on greater retention of riparian trees and other vegetation, an approach that for fish and wildlife habitat assumes significant ecological functions and benefits will follow over extended spatial and temporal intervals. Research continues to clarify ecological features and functions of headwater areas, but policy and management remain challenging because of highly variable observations downstream and because socioeconomic concerns are inconsistently addressed. Given these limitations, our policies may continue to confound decisionmakers and discourage many forest owners and managers, while also adding to an array of unintended local and global environmental consequences.

A Synthesis of the Ecology of Headwater Streams and their Riparian Zones in Temperate Forests - John S. Richardson; Robert J. Danehy (Forest Science, 2007)
Headwater streams and their riparian areas, i.e., headwater systems, differ from larger streams in a number of fundamental ways that shape their characteristic biological communities. We focus on three distinguishing characteristics of headwater systems in temperate, forested landscapes, particularly in the North American Pacific Northwest, in contrast to larger streams. Small channel size and closed canopy create a physical template of reduced light inputs, strong local microclimate gradients, higher input rates of organic matter, and low primary production. The predominance of organic matter inputs as the primary source of biologically available energy promotes detritus-based communities. Second, headwaters are either fishless or have smaller fish populations (numerically and/or size-wise), leading to reduced effects of fish predation and fewer, if any, piscivores along headwaters. A third difference is the dominant disturbance regime associated with loss of surface flow. Other disturbances include infrequent and large mass failures, e.g., channelized debris flows, but low flows are a characteristic of headwaters and not larger streams. There have been few designed comparisons of headwater systems with larger channels. Still, evidence indicates that headwaters form distinct systems contrasted with larger channels such that management should not treat them simply as big streams writ small.

Estimating Air Temperature Profiles in Forest Canopy Using Empirical Models and Landsat Data - Jiansheng Yang; Yeqiao Wang; David R. Miller (Forest Science, 2007)
The objective of this study was to characterize and predict the air-temperature profiles in forest canopy using empirical models and Landsat-7 Enhanced Thematic Mapper Plus (ETM+) thermal infrared (TIR) data. For each hour of the day, empirical models were developed using the air temperatures measured in a mixed forest in Tolland, Connecticut during the summer of 2001. Air-temperature profiles measured on eight randomly selected days over the study period were used to evaluate the models' performance. The results show high agreement between model-predicted temperatures and field observations (R2=0.96 and RMSE=0.5°C). Forest canopy-surface temperature was estimated from Landsat ETM+ TIR data and then applied on the empirical model at 10:30 to predict air temperatures below the forest canopy. Compared with field-measured air temperatures on the same day, good agreement (R2=0.80 and RMSE=0.7°C) was obtained between predicted and observed air-temperature profile in this mixed forest. This study implies that Landsat TIR data combined with empirical models have the potential to characterize and further predict the air-temperature profile in forest canopies.

Cruz, M.G., M.E. Alexander, and R.H Wakimoto. 2004. Modeling the likelihood of crown fire occurrence in conifer forest stands. For. Sci. 50(5):640–658. (Forest Science, 2007)

Evaluation of Fumigants, EPTC Herbicide, and Paenibacillus macerans in the Production of Loblolly Pine Seedlings - Michelle M. Cram; Scott A. Enebak; Stephen W. Fraedrich; Lew D. Dwinell; Stanley J. Zarnoch (Forest Science, 2007)
Chloropicrin fumigation, Eptam 7-E (EPTC) herbicide, and Paenibacillus macerans seed treatments were evaluated as alternatives to fumigation with methyl bromide/chloropicrin for loblolly pine (Pinus taeda L.) seedling production at three nurseries in the southern United States. A treatment of metam sodium/chloropicrin was also evaluated at one nursery. Seedling density was unaffected by fumigation and EPTC treatments at all nurseries. Seedling diameter and shoot weight were greater in some chloropicrin treatments during the first year at the southern Georgia nursery. The only measurable disease losses were caused by a nematode, Longidorus americanus, at the southern Georgia nursery. Soil-borne population densities of Pythium and Fusarium spp. did not significantly differ between methyl bromide and the other fumigant treatments at any nursery. Chloropicrin controlled nutsedge (Cyperus spp.) in the loamy sand soils at the southern Georgia nursery, but there were no differences between the control and the fumigant treatments at the Alabama nursery, and nutsedge was rarely found at the northern Georgia nursery. The herbicide EPTC had no effect on nutsedge when compared to the controls at all nurseries and the effects of the bacterial seed treatment were inconsistent among the nurseries. Chloropicrin and metam sodium/chloropicrin can be effective alternatives to methyl bromide for reducing soil-borne fungi and nematodes, but the effectiveness of chloropicrin for nutsedge control may be affected by soil type.

Compatible Estimators of the Components of Change for a Rotating Panel Forest Inventory Design - Francis A. Roesch (Forest Science, 2007)
This article presents two approaches for estimating the components of forest change utilizing data from a rotating panel sample design. One approach uses a variant of the exponentially weighted moving average estimator and the other approach uses mixed estimation. Three general transition models were each combined with a single compatibility model for the mixed estimation approach. The four resulting estimation systems are compared and contrasted in a sample simulation study covering four simulated populations.

Partitioning Error Components for Accuracy-Assessment of Near-Neighbor Methods of Imputation - Albert R. Stage; Nicholas L. Crookston (Forest Science, 2007)
Imputation is applied for two quite different purposes: to supply missing data to complete a data set for subsequent modeling analyses or to estimate subpopulation totals. Error properties of the imputed values have different effects in these two contexts. We partition errors of imputation derived from similar observation units as arising from three sources: observation error, the distribution of observation units with respect to their similarity, and pure error given a particular choice of variables known for all observation units. Two new statistics based on this partitioning measure the accuracy of the imputations, facilitating comparison of imputation to alternative methods of estimation such as regression and comparison of alternative methods of imputation generally. Knowing the relative magnitude of the errors arising from these partitions can also guide efficient investment in obtaining additional data. We illustrate this partitioning using three extensive data sets from western North America. Application of this partitioning to compare near-neighbor imputation is illustrated for Mahalanobis- and two canonical correlation-based measures of similarity.

Incorporating Whole-Stand and Individual-Tree Models in a Stand-Table Projection System - Quang V. Cao (Forest Science, 2007)
A stand table provides number of trees per unit area for each diameter class. This article presents three methods to project a current stand table into the future by predicting mortality and diameter growth for each diameter class by use of an individual-tree model. The stand table was then adjusted to produce the same total number of trees and basal area per hectare as predicted from the whole-stand model. The three methods evaluated in this study were stand table adjustment, constrained least squares (LS), and modified constrained LS. Data from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) showed that incorporating the individual-tree model helped improve the projection of stand tables, as compared to a previous approach. The three methods produced comparable results; error indices from these methods were within 5% of one another. The constrained LS method consistently provided the best fit (lowest error indices) as compared to the other methods.

Determinants of Forest Land Prices in Northern Minnesota: A Hedonic Pricing Approach - Stephanie A. Snyder; Michael A. Kilgore; Rachel Hudson; Jacob Donnay (Forest Science, 2007)
A hedonic price model was developed to analyze the market for undeveloped forestland in northern Minnesota. The data included 387 forestland parcels purchased in 2001 or 2002. Information describing parcel physical characteristics, amenity features, merchantable timber volume, development trends, terms of financing, and several proximity, distance, and adjacency conditions were tested for their influence on forestland prices. The model's independent variables collectively explained approximately 50% of the variation in per hectare sale price. The method by which forestland sales were financed, road access and density, proximity to population centers, and presence of lake or river frontage had the largest positive influences on per hectare sale prices. Adjacency to public land had an unexpectedly large, negative influence on sale price. Importantly, a parcel's merchantable timber volume was not found to be a significant predictor of forestland sale price. In general, forestland markets were driven by three major influences: land development pressures, presence of or close proximity to a water body, and the use of contract for deed financing.

Spatial Patterns of Modern Period Human-Caused Fire Occurrence in the Missouri Ozark Highlands - Jian Yang; Hong S. He; Stephen R. Shifley; Eric J. Gustafson (Forest Science, 2007)
The spatial pattern of forest fire locations is important in the study of the dynamics of fire disturbance. In this article we used a spatial point process modeling approach to quantitatively study the effects of land cover, topography, roads, municipalities, ownership, and population density on fire occurrence reported between 1970 and 2002 in the Missouri Ozark Highland forests, where more than 90% of fires are human-caused. We used the AIC (Akaike information criterion) method to select an appropriate inhomogeneous Poisson process model to best fit to the data. The fitted model was diagnosed using residual analysis as well. Our results showed that fire locations were spatially clustered, and high fire occurrence probability was found in areas that (1) were public land, (2) within 6 km to 17 km of municipalities, and (3) <500 m from roads where forests are accessible to humans. In addition, fire occurrence probability was higher in pine-oak forests on moderate (<25 degree) slopes and xeric aspects and at higher (>270 m) elevations, reflecting the effects of natural factors on fire occurrence. The results serve as a provisional hypothesis for expanding fire risk estimation to surrounding areas. The spatial scale of analysis (approximately 1 ha) provides new information to guide planning and risk reduction efforts.

Insect-Fungal Complex Associated with Loblolly Pine Decline in Central Alabama - Lori G. Eckhardt; Ann M. Weber; Roger D. Menard; John P. Jones; Nolan J. Hess (Forest Science, 2007)
Loblolly pine decline, characterized by an expanding area of declining and dead trees, is becoming increasingly prevalent in loblolly pine (Pinus taeda L.) forests in central Alabama. A 3-year study was conducted to determine the fungal, root, and lower stem-infesting insect, and/or soil parameters associated with this decline. Hylastes salebrosus, Hylastes tenuis, Pachylobius picivorus, and Hylobius pales were significantly more abundant in declining plots than in asymptomatic plots. Root- and lower stem-infesting insects consistently carried Leptographium terebrantis, L. procerum, and L. serpens. Sampled roots had high levels of root damage, mortality, and staining typically associated with Leptographium species. Root damage and mortality preceded aboveground symptoms of short chlorotic needles, sparse crowns, reduced radial growth, and tree mortality. A sequence of biotic and abiotic factors is proposed as the cause of loblolly pine decline complex.

Comparison of Fuzzy and Statistical Approaches in Multicriteria Decisionmaking - Annika Kangas; Pekka Leskinen; Jyrki Kangas (Forest Science, 2007)
Criteria used to measure ecological or social sustainability of forestry often include qualitative ones. Fuzzy additive weighting has been proposed for using qualitative data in the form of linguistic variables. It is, however, possible to formulate a linguistic problem also using statistical distributions. We compared the fuzzy and statistical approach in a linear additive weighting problem on a woodlot owned by UPM-Kymmene. The results of fuzzy additive weighting showed high uncertainty concerning the decision compared to the statistical approach. In fuzzy analysis, the best option was unclear and the risk involved in the decision seemed high, while in statistical analysis the best option was clear and the risks involved seemed negligible. The uncertainty present in the fuzzy approach did not correspond to the 95% confidence intervals, but rather to the extreme values of statistical analysis. It can be concluded that the fuzzy approach represents ignorance in the true criterion values, while the statistical approach represents variability in them. It can also be concluded that the fuzzy approach represents decisionmaking under uncertainty, while the statistical approach represents decisionmaking under risk. If probability distributions for the uncertain data can be obtained, the statistical approach is more useful. Otherwise, the fuzzy approach should be used.

Bivariate Distribution Modeling with Tree Diameter and Height Data - Mingliang Wang; Keith Rennolls (Forest Science, 2007)
The Logit-Logistic (LL), Johnson's SB, and the Beta (GBD) are flexible four-parameter probability distribution models in terms of the (skewness-kurtosis) region covered, and each has been used for modeling tree diameter distributions in forest stands. This article compares bivariate forms of these models in terms of their adequacy in representing empirical diameter–height distributions from 102 sample plots. Four bivariate models are compared: SBB, the natural, well-known, and much-used bivariate generalization of SB; the bivariate distributions with LL, SB, and Beta as marginals, constructed using Plackett's method (LL-2P, etc.). All models are fitted using maximum likelihood, and their goodness-of-fits are compared using minus log-likelihood (equivalent to Akaike's Information Criterion, the AIC). The performance ranking in this case study was SBB, LL-2P, GBD-2P, and SB-2P.

Carbon and Nitrogen Cycling in Southwestern Ponderosa Pine Forests - Stephen C. Hart; Paul C. Selmants; Sarah I. Boyle; Steven T. Overby (Forest Science, 2006)
Ponderosa pine forests of the southwestern United States were historically characterized by relatively open, parklike stands with a bunchgrass-dominated understory. This forest structure was maintained by frequent, low-intensity surface fires. Heavy livestock grazing, fire suppression, and favorable weather conditions following Euro-American settlement in the late 19th century resulted in a dramatic increase in pine regeneration. Today, many of these forest stands have high stand densities with low understory production, and are susceptible to infrequent, stand-replacing fires. The primary objective of our study was to better characterize the contemporary carbon (C) and nitrogen (N) cycling processes in relatively unmanaged southwestern ponderosa pine stands. We then compared these ecosystem conditions with those of an adjacent stand that had received an ecological restoration treatment that included thinning and prescribed burning. Our results suggest that N availability and aboveground net primary productivity (ANPP) of trees in these forests are low compared to other forests. Restoration treatments decreased ANPP but increased the proportion of ANPP in woody tissues. These treatments also increased soil respiration, water availability, temperature, and net nitrification, but had no effect on net N mineralization and microbial N. We speculate that the understory response to restoration treatments is a key factor affecting the overall ecosystem response in these forests.

Effect of Edge Trees on Harvester Positioning in Thinning - Heikki Ovaskainen; Jori Uusitalo; Tuomo Sassi (Forest Science, 2006)
The objective of this study was to discover the influence of edge trees, the trees along the side of the strip road, on the positioning of modern single-grip harvester during the first commercial thinning. The results indicate that there is one main working location in the strip road where the harvester is positioned in a distance of two consecutive edge trees. This main location is determined by an edge tree located about 1.2 m behind the boom base. There are also other working locations within a certain distance but in most cases the harvester was positioned same way to the main location, which enables the least restricted boom operations in the boom working sector. Positioning the harvester according to the edge trees does not explain the considerable productivity differences among experienced harvester operators, but the awareness and significance of the edge trees give trainees a valuable basis for outlining and planning work in early stages of training. The present findings are also beneficial from the cutting damage and harvester configuration points of view.

Forest Volume and Biomass Estimation Using Small-Footprint Lidar-Distributional Parameters on a Per-Segment Basis - Jan A.N. van Aardt; Randolph H. Wynne; Richard G. Oderwald (Forest Science, 2006)
This study assessed a lidar-based, object-oriented (segmentation) approach to forest volume and aboveground biomass modeling. The study area in the Piedmont physiographic region of Virginia is composed of temperate coniferous, deciduous, and mixed stands. Segmentation objects, hierarchical in terms of area and ranging from 0.035 to 5.632 ha/object, were created using a lidar-derived canopy height model. Horizontal point (basal area) samples were used to calculate volume and aboveground biomass. Per-object lidar point (per return height and intensity) distributional parameters were extracted from small-footprint lidar. Adjusted R 2 and Mallow's Cp metrics were used to select models for the range of segmentation results. Selected variables included intensity-based and structurally related first through fifth return height parameters. Object-based modeling (adjusted R 2 = 0.58–0.79; various object sizes) resulted in distinct improvements over stand-based attempts (adjusted R 2 = 0.40–0.73; majority adjusted R 2 < 0.50). Adjusted R 2 and RMSE values for deciduous volume (0.59; 51.15 m3/ha) and biomass (0.58; 37.41 Mg/ha) were better than those found for another, plot-based study in the study area. Coniferous R 2 values for volume (0.66) and biomass (0.59) were lower than previous studies, which was attributed to variability within the relatively narrow volume range (6.94–50.93 m3/ha).

Tree-Level Models for Predicting Lumber Volume Recovery of Black Spruce Using Selected Tree Characteristics - Chuangmin Liu; Z.H. Jiang; S.Y. Zhang (Forest Science, 2006)
Four model forms (linear, polynomial, power, and exponential) and their extensions with different independent variables were studied for their predictive ability for lumber volume recovery from black spruce (Picea mariana [Mill.] B.S.P.) trees at two types of sawmills (a stud mill and a random length mill) using basic tree characteristics (dbh, tree height, and stem taper). Of the three tree characteristics, dbh was identified as having the most predictive ability for lumber volume recovery. We found that all models predicted lumber volume recovery more precisely for small-sized and medium-sized (≤23 cm) trees than for large-sized (>03E23 cm) trees. In terms of the selected statistical criteria such as adjusted R2, root-mean-square error (RMSE), predicted error sum of squares (PRESS), and prediction error, the best models for predicting lumber volume recovery were considered to be the following forms for both types of sawmills: (1) the second-order polynomial function with dbh alone, (2) the polynomial function with an interaction term of squared dbh and tree height, and (3) the power function with dbh and tree height. For both types of sawmills, the three final fitted model forms accounted for over 91% of the total variation. Model validation using independent data from a stud mill indicated that by using measured tree characteristics the three model forms were able to accurately and precisely predict lumber volume recovery, especially from small- and medium-sized trees.

Comparison of Distance-Dependent and Distance-Independent Stand Growth Models—Is Perfect Aggregation Possible? - Tero Kokkila; Annikki Mäkelä; Alain Franc (Forest Science, 2006)
Selecting a suitable level of accuracy in stand growth estimations is a question of practical importance. A detailed model is more complicated and demands more initial information from the user to produce reliable results. Despite being correct and more precise, it may well be that the more detailed results give no practical bonus value. The essential part of the estimations could also have been received with coarser means. We have used three levels of stand description accuracy. The first is a mean tree model (MTM), where all trees are assumed identical. The second is a distribution-based model (DBM), where size differences are allowed. Both versions are distance-independent and the spatial configuration of the stand is considered random. The third is a spatially explicit model (SEM), where all trees are described individually and their spatial locations are taken into account. The core dynamics in all models are kept the same, so a previous model is a straightforward aggregation of the latter one. The possibility of a perfect aggregation was examined both theoretically and by practical simulations. A process-based stand growth model ACROBAS was used to simulate the different levels of aggregation. The results demonstrate that under the Poisson assumption of stand spatial configuration there are hardly any differences among model aggregations. As mortality is not totally random in the SEM, the Poisson assumption does not hold through the whole simulation period. As the spatial configuration eventually tends toward regularity, the total growth in the stand is somewhat increased, which is evident in variables such as total stem volume and foliage mass. However, mean height and stocking density developments are almost identical in all models. This suggests that the mean height is “an almost perfect𠇍 aggregation variable.

Predicting the Plot Volume by Tree Species Using Airborne Laser Scanning and Aerial Photographs - Petteri Packalé n; Matti Maltamo (Forest Science, 2006)
Several studies have indicated that forest characteristics can be accurately predicted using airborne laser scanner (ALS) data, but there are very few studies in which species-specific forest characteristics have been estimated. This article compares two approaches for determining species-specific volumes at plot level by combining ALS data with aerial photographs. The first approach consists of two stages: (1) prediction of total volume using ALS data, and (2) assignment of this total volume to tree species by fuzzy classification and aerial photographs, in which three fuzzy classification methods were tested. In the second approach, volumes by tree species and the total volume are predicted simultaneously using a nonparametric k-most similar neighbor (k-MSN) method based on both ALS data and aerial photographs in one phase. The test area, located in Finland, consists of 463 sample plots. Species-specific volumes were estimated for pine, spruce, and the deciduous trees as a species group, total volume being the sum of the species-specific volumes. The k-MSN method produced considerably more accurate estimates for the species-specific volumes than any fuzzy classification method, the relative RMSEs for the volumes of pine, spruce, and deciduous trees being 45.50%, 61.98%, and 92.30%, respectively, and that for the total volume 23.86%.

Best Predictors for Postfire Mortality of Ponderosa Pine Trees in the Intermountain West - Carolyn Hull Sieg; Joel D. McMillin; James F. Fowler; Kurt K. Allen; José F. Negron; Linda L. Wadleigh; John A. Anhold; Ken E. Gibson (Forest Science, 2006)
Numerous wildfires in recent years have highlighted managers' needs for reliable tools to predict postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees. General applicability of existing mortality models is uncertain, as researchers have used different sets of variables. We quantified tree attributes, crown and bole fire damage, ground fire severity, and insect presence from a total of 5,083 trees in four 2000 wildfires in four Intermountain states. Crown scorch (percentage) and consumption (percentage) volume collectively accounted for the majority of predictive capacity in all four individual models and in the pooled four-site model. The addition of tree diameter and presence of Ips beetles in the pooled model slightly improved predictive power. Four other statistically significant variables added little to the pooled model's predictive ability. The pooled model correctly classified 3-year postfire mortality of 89.9% of the trees and had a receiver operating characteristic (ROC) score of 0.96. In the external validation step, the model correctly classified 3-year postfire mortality of 96% of 1,361 trees in a 2001 wildfire. Our results and a number of previous studies suggest that a two-variable model using percentage crown scorch volume and crown consumed volume will have applicability beyond the Intermountain West.

Historical Fire Cycles in the Canadian Rocky Mountain Parks - Charles E. Van Wagner; Mark A. Finney; Mark Heathcott (Forest Science, 2006)
The subject of this article is the fire history of seven contiguous national and provincial parks in the Canadian Rocky Mountains, four to the east of the continental divide and three to the west. Seven centuries of time-since-fire data were combined and arrayed in three sets: all seven parks together, then the east-side and west-side groups separately. Fire cycles were estimated by four different methods: two of them statistical and two deterministic. Statistical evidence of distinct changes in fire regime, always toward a lower burning rate, was uncovered, with transitions in 1760 and 1940 on the east side, and in 1840 on the west side. The principal conclusions were: The seven parks as a unit supported a fire cycle of 60–70 yr for nearly five centuries before 1760. The burning rate then dropped sharply and a longer cycle of about 175 yr prevailed until 1940. Fire history in the combined large parks on the east side was similar to the above. By contrast, the smaller west-side parks group sustained a fire cycle of about 90 yr for at least five centuries before 1840; the burning rate then decreased irregularly to 2000. On the east side, the near absence of burned area after 1940 was attributed to the onset of effective fire protection. Possible prior causes of the earlier transitions on east and west sides include changes in climate or aboriginal fire practices, but this issue is left unresolved.

Calibrating a Generalized Diameter Distribution Model with Mixed Effects - Mathieu Fortin; Chhun-Huor Ung; Louis Archambault; Jean Bégin (Forest Science, 2006)
This article proposes a mixed model approach as an alternative to the traditional parameter prediction method in diameter distribution modeling. Unthinned and thinned plots established in mixed stands were used for calibrating a generalized diameter distribution model. The model was based on a two-parameter Weibull cumulative density function (cdf). This cdf was linearized through a complementary log–log link function. Plot random effects were included to account for autocorrelation and the dependent variable, i.e., cumulative stem frequency, was assumed to follow a binomial distribution. With respect to the parameter prediction method, this mixed model approach may generate a consistent estimator with consistent and unbiased variance for the vector of parameters when the variance-covariance matrix of the error terms is properly parameterized. Moreover, the approach enables a better assessment of the different variance components. For the whole group of plots, it provides a predicted average diameter distribution. At the plot level, the random effects can be considered as a departure from this average distribution. As long as the diameter distributions of the individual plots do not exhibit major departures from unimodality, the method proposed in this study should be used to calibrate generalized diameter distribution models.

A Generalized Approach for Modeling and Localizing Stem Profile Curves - Guillermo Trincado; Harold E. Burkhart (Forest Science, 2006)
The Max and Burkhart segmented taper equation was fitted using nonlinear mixed-effects modeling techniques to account for within- and between-individual variation in loblolly pine (Pinus taeda L.) stem profiles. Within- and between-tree residual variances and spatial autocorrelation between residuals were incorporated in the model with an error variance function and a continuous autocorrelation structure, respectively. However, most of the residual autocorrelation was accounted for by including random effects. Upper stem diameter measurements were used to estimate random effects parameters using an approximate Bayesian estimator, which localized stem profile curves for individual trees. The procedure was tested with an independent data set. Measures of precision and bias showed that upper stem diameter measurements and subsequent estimates of random effects improved the predictive capability of the taper equation mainly in the lower portion of the bole. The method can localize stem curves for trees growing under different site and management conditions. It also represents a general framework that can be applied to other taper equation forms, increasing their flexibility and efficiency in prediction for local conditions.

Simulating Fire Spread with Landscape Management Scenarios - Jacob J. LaCroix; Soung-Ryoul Ryu; Daolan Zheng; Jiquan Chen (Forest Science, 2006)
Collectively, landscape structure, fuel loading, and weather control wildland fires. Our objective was to examine the impacts of landscape structure, weather and fire-ignition location on fire spread using FARSITE. We simulated surface fires in the Chequamegon National Forest, Wisconsin, on five landscapes: a control and four harvested landscapes created using HARVEST by varying the amount (2% and 4%) and method of harvesting (i.e., clustered and dispersed), labeled C2, C4, D2, and D4. We applied three levels of precipitation and wind speed to examine weather influences. We found that fire-ignition location had the strongest effect on fire spread, followed by rain. The high-rain scenario (twice the actual rainfall) decreased burned area by an average of 241 ha (6.1%) for simulated 15-day surface fires, whereas the low-rain scenario (half of actual rainfall) increased burned area by an average of 74 ha (1.8%). The maximum size of burned area decreased in all harvest scenarios by 90 ha (1.6%), 143 ha (2.6%), 168 ha (3.1%), and 201 ha (3.7%), respectively, for landscapes D2, C2, D4, and C4. We concluded that management at the ignition location is critical and landscape-level management may be adapted to influence landscape predisposition to fire spread.

Traditional Trees of Pacific Islands: Their Culture, Environment, and Use (Forest Science, 2006)

Capital Structure in the United States Forest Products Industry: The Influence of Debt and Taxes - Brooks C. Mendell; Tymur Sydor; Neena Mishra (Forest Science, 2006)
This article investigates financing practices across firms in the forest products industry by studying the relationship between debt and taxes hypothesized in finance theory. In testing the theoretical relationship between taxes and capital structure for 20 publicly traded forest industry firms for the years 1994–2003, we find a negative relationship between profitability and debt, a positive relationship between nondebt tax shields and debt, and a negative relationship between firm size and debt. All three results run counter to theoretical expectations. Results indicate that, controlling for size, firms in the forest products industry with higher market valuations and pretax earnings used more conservative financing strategies. Also, the article develops a dynamic panel model with fixed effects for each firm and residualization to address issues of multicollinearity.

Ecological Modeling for Resource Management (Forest Science, 2006)

An Econometric Analysis of the Effect of Forest Dependence on the Economic Well-Being of Canadian Communities - Nancy Leake; Wiktor L. Adamowicz; Peter C. Boxall (Forest Science, 2006)
This study examines how changes in economic activity in forestry, expressed as forest dependence at a census subdivision level (CSD), affected measures of economic well-being. The empirical models used to address this question were developed and estimated using random effects panel and two-stage least-squares estimators using data from the 1986, 1991, and 1996 Canadian census. The results illustrate the contribution of economic diversity to income growth and poverty reduction. However, the results also suggest that forest dependence was positively and significantly related to unemployment rates and to the incidence of poverty for people in private households. Forest dependence was shown to have little or no effect on median household income and the distribution of income within CSDs. These relationships were assessed while holding constant other factors expected to affect community level economic well-being, including economic diversity, trade exposure, and aggregate demand.

Bootstrap Simulation and Response Surface Optimization of Management Regimes for Douglas-Fir/Western Hemlock Stands - Jingjing Liang; Joseph Buongiorno; Robert A. Monserud (Forest Science, 2006)
A method was proposed to simulate forest stand growth, timber prices, and interest rates by distribution-free bootstrapping, and then optimize management controls for economic and ecological objectives by response surface analysis. The method was applied to Douglas-fir/western hemlock stands to predict the effects on economic and ecological objectives of management alternatives defined by the cutting cycle, C, the residual stand basal area, B, the diameter of the largest tree, D, and the ratio, q, of the number of trees in adjacent diameter classes. The effects were described with response surfaces, which were used to determine the best combinations of B, q, and C for each management criterion. Adjusting B, q, and C could control for 97 to 99% of the variability in the expected value of species diversity, size diversity, percentage of peeler logs, and basal area, and for 80 to 90% of the variability in land expectation value and annual production. Economic and ecologic criteria were generally most sensitive to the q ratio, the residual basal area, and the cutting cycle. Annual production was negatively correlated with tree size diversity and wood quality. There was no apparent conflict between stand diversity and wood quality.

Modeling Postfire Mortality of Ponderosa Pine following a Mixed-Severity Wildfire in the Black Hills: The Role of Tree Morphology and Direct Fire Effects - Tara L. Keyser; Frederick W. Smith; Leigh B. Lentile; Wayne D. Shepperd (Forest Science, 2006)
We examined the relationship among tree size, crown and stem damage, and 5 years of postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex. P. & C. Laws.) in the Black Hills following a large, mixed-severity wildfire. We measured tree morphology and direct fire effects on 963 trees and assessed individual tree mortality annually from 2001 to 2005. We used logistic regression to model tree mortality as a function of tree morphology (dbh) and bark thickness (BARK) and direct fire effects [percentage of the live crown scorched (PSCOR) and basal char measured as the percentage of the bole charred below 30 cm (CHAR)]. Models using dbh and BARK were modeled separately due to correlation between the variables. In all models, mortality decreased with increasing dbh and BARK and increased with increasing PSCOR and CHAR. Basal char contributed to the mortality of trees less than 40 cm but became less influential as dbh and BARK increased. Overall, probability of mortality modeled as a function of dbh, PSCOR, and CHAR correctly predicted the status of 78% of trees, whereas the model predicting mortality as a function of BARK, PSCOR, and CHAR had an increase in prediction accuracy of only 1%.

Research and Development Operations and Foreign Expansion of Multinational Companies: Evidence from Forest Industry Microdata - Susanna Laaksonen-Craig; Jussi Uusivuori (Forest Science, 2006)
This article examines the impacts of research and development on the mode of multinational expansion (exports versus foreign sales) by forest products companies, and the effects of firms' international strategy on the level of research and development investments. A theoretical model of imperfect competition between international companies is derived and company-level data representing Finnish forest industries are used. The results indicate that the firms' own research and development investments helped, at least during the 1980s, their foreign expansion by favoring the firms' exports rather than foreign sales. External research and development investments by other companies were substitutes for a firm's own investment on research and development in the 1980s, but this effect seems to have disappeared toward the 1990s. There have not appeared to be any significant spillover effects from the research and development activities across the firms.

Bird–Habitat Relationships in Grand Fir Forests of the Blue Mountains, Oregon - Rex Sallabanks; Robert A. Riggs; Lynda E. Cobb; Steven W. Dodson (Forest Science, 2006)
During the breeding seasons of 1994–1996, we sampled bird communities and habitat characteristics in grand fir (Abies grandis) forests of the Blue Mountains, northeastern Oregon, at the stand- and landscape-level with the objective of explaining variation in the composition and abundance of forest avifauna. We analyzed data from 77 forest stands that varied in size from 16 to 213 ha. Canonical correlation analysis (CANCOR) indicated that stand-level features accounted for more variance in the relative abundance of bird species than did landscape-level features (35 versus 14%, respectively). The most important stand-level features were overstory canopy cover, density of large-diameter live trees, and understory structure (especially herbs and shrubs). Important landscape features for predicting the abundance of species within a forest stand included stand isolation and the percentage of surrounding landscape within a 4-km radius that was occupied by forest cover. Using the information-theoretic approach to model selection and inference, we built models of bird–habitat relationships to forecast abundance of 24 species. Consistent with CANCOR results, species–specific habitat models were dominated by stand-level variables. Overstory cover was a significant predictor of abundance for 17 of 24 species modeled (71%). We conclude that in forests represented by our sample, management for most avian species can be usefully focused on within-stand dynamics of structure, but that efforts to forecast abundance of some species can be enhanced by integration of landscape metrics as well.

Landscape-Level Impact of Beech Bark Disease in Relation to Slope and Aspect in New York State - I.A. Munck; P.D. Manion (Forest Science, 2006)
During the past 40 years, the beech bark disease complex has destabilized the beech component of New York State forests, but a selected portion of the American beech (Fagus grandifolia) population has attained a sustainable forest structure. The influence of slope and aspect in relation to beech bark disease on the sustainability of American beech populations was evaluated. There were differences in the proportion of American beech trees with signs of Neonectria spp. and beech scale (Cryptococcus fagisuga) on eastern and western aspects on slopes ≥16%. American beech populations on northern, northeastern, eastern, southeastern, and southern aspects on slopes ≥16% (23–29% of the sample) displayed diameter distributions that would sustain the current forest structure. In all other sites, observed percentage mortality in the large-diameter classes was higher than predicted, suggesting a future shift in forest structure toward lower densities of large trees in these sites.

Total Factor Productivity Growth in the Sawmill and Wood Preservation Industry in the United States and Canada: A Comparative Study - Daowei Zhang; Rao V. Nagubadi (Forest Science, 2006)
By using the Törnqvist-Theil index approach, we analyze trends in total factor productivity (TFP) growth in the United States and Canadian sawmill and wood preservation industries (NAICS 3211) between 1958 and 2003. The results indicate that the TFP grew at an average annual compound rate of 1.11% due to higher growth in aggregate outputs by 1.42% and a smaller growth in aggregate inputs by 0.31% in the United States. In Canada, TFP grew at a smaller average annual compound rate of 0.61% as a result of growth in aggregate outputs and inputs by 3.57% and 2.94%, respectively. Although productivity growth for production worker input was similar in both countries, large gaps in productivity growth existed for nonproduction workers, material, capital, and energy inputs. The gap in TFP growth between the two countries appears to have widened since 1987, primarily due to the differences in capital stock growth. Volatility in lumber prices after 1991 might have also played a role, as the Canadian industry could not adequately respond to changing market situations in the face of uncertainty and trade barriers on softwood lumber exports to the United States.

Nord-Larsen, T. 2006. Modeling individual-tree growth from data with highly irregular measurement intervals. For. Sci. 52(2):198–208 (Forest Science, 2006)

The Bioengineered Forest: Challenges for Science and Society (Forest Science, 2006)

Early Evaluation of Intra- and Inter-Provenance Hybrids of Loblolly Pine for Planting in Piedmont Regions of the Southern United States - Paraskevi G. Alizoti; Bailian Li; Steven E. McKeand (Forest Science, 2006)
Two intra-provenance [Atlantic Coastal (C×C), Piedmont (P×P)] and two inter-provenance [Atlantic Coastal × Piedmont (C×P), Piedmont × Atlantic Coastal (P×C)] loblolly pine (Pinus taeda L.) populations, represented by 80 polycross families, were assessed for height, volume, and survival in five Piedmont regions at four years of age. The hybrid populations (C×P, P×C) were intermediate among the pure populations (C×C, P×P). Across and within regions the C×P hybrids were significantly taller and more productive in volume than the pure P×P, with performance comparable to that of C×C. The C×P hybrids exhibited stronger additive genetic control for both height and volume across and within regions, except for the two inland regions, where the P×C hybrids' genetic control for height was stronger. Stability of performance in height and volume varied among families within populations. These early results suggest that the C×P hybrids will perform better in milder Piedmont environments, while the P×C hybrids could be suitable for more inland and northern Piedmont sites. Long-term evaluation of population performance and adaptability is essential before implementing such a plan in the Piedmont.

Innovativeness in the North American Softwood Sawmilling Industry - Pablo Crespell; Christopher Knowles; Eric Hansen (Forest Science, 2006)
The North American forest products industry has traditionally maintained a production orientation and a commodity mentality toward operations, with much of the industry following a low-cost strategy and concentrating on wood fiber recovery. The propensity to innovate (innovativeness) is important for maintaining firm competitiveness. To assess industry practices with respect to innovativeness, United States and Canadian softwood sawmills were surveyed. Respondents rated themselves more innovative with respect to manufacturing processes as compared to product and business systems innovations. Innovativeness and market orientation were found to be positively correlated. High- and medium-innovative mills were consistently different (e.g., more market-oriented, more structured new product development processes) from low-innovative mills.

Factors that Influence Administrative Appeals of Proposed USDA Forest Service Fuels Reduction Actions - David N. Laband; Armando González-Cabán; Anwar Hussain (Forest Science, 2006)
Using the database developed by the General Accounting Office on proposed fuels reduction actions on federal lands in 2001 and 2002, we conduct probit regression analysis to identify factors that significantly affect the likelihood of administrative appeal. The likelihood of appeal of a proposed fuels reduction action is significantly increased by (1) the size of area affected, (2) the number of proposed activities at the site, (3) when one of the stated purposes is commodity production (timber and sawlogs), (4) when one of the stated purposes is reduction of project-generated fuels, (5) implementation involves prescribed burning or mechanical thinning, and (6) the presence of at least one species of mammal at risk of extinction in the immediate vicinity of the site. Conversely, the likelihood of appeal is significantly reduced if (7) implementation is handled by Forest Service personnel or using a service contract, and (8) the proposed action is located in a Wildland–Urban Interface area. However, we also observe persistent regional effects, with fuels reduction proposals in Region 1 (3, 6, 8) characterized by a significantly higher (lower) likelihood of appeal than proposals in the other regions.

Competitiveness in the Sawmills and Wood Preservation Industry in the United States and Canada - Rao V. Nagubadi; Daowei Zhang (Forest Science, 2006)
We examine relative prices, relative productivity levels, and competitiveness in the sawmills and wood preservation industry in the United States and Canada between 1958 and 2003 by using purchasing power parities and bilateral translog production function. Our results show that the competitiveness of the Canadian industry is facilitated by higher relative productivity levels and depreciation of the Canadian dollar relative to the US dollar on both inputs and outputs in earlier periods, and only due to depreciation of the Canadian dollar in later periods. The average annual rate of productivity growth was higher for the US industry. Although Canadian relative productivity levels were higher before 1994, the US industry's relative productivity level eventually surpassed the Canadian industry.

Timber Sale Characteristics and Competition for Public Lands Stumpage: A Case Study from the Lake States - Larry A. Leefers; Karen Potter-Witter (Forest Science, 2006)
The U.S. stumpage pricing system is often presented as a market-based approach that should be adopted by Canadian provinces. We compare four public agency stumpage pricing systems in the Lake States (Michigan, Minnesota, and Wisconsin) with many similar features, but their differences lead to diverse starting points in the stumpage pricing process. Further, comparisons between the Michigan Department of Natural Resources (MiDNR) and the USDA Forest Service indicate that there is considerably more competition for MiDNR sales. This is due to institutional differences between the agencies. We estimated hedonic pricing models for Lake States national forest and MiDNR timber sales to determine which sale and institutional characteristics influenced stumpage prices. The final models for stumpage price centered on species–product composition of sales, number of species and products, regional location, administratively set sale contract length, and sale timing, competition, and firm size. Empirical results illustrate that models within the same geographic region are not readily transferable to another ownership. This will complicate efforts for cross-border comparisons of hedonic pricing results. Importantly, the models do provide insights regarding the sign and significance of variables. We conclude that the U.S. systems are not readily adaptable to Canadian regions in which little competition exists.

Transaction Evidence Appraisal: Competition in British Columbia's Stumpage Markets - Kurt Niquidet; G. Cornelis van Kooten (Forest Science, 2006)
As a potential resolution to the softwood lumber dispute, the US Department of Commerce recommends that administered stumpage prices in Canada be determined using information from competitive timber auctions. Previous research indicates that the degree of competition significantly influences bidding behavior. In this article, therefore, a truncated hedonic timber sale model was developed to investigate the influence of competition on stumpage markets in the interior of British Columbia. Results indicate that lower bids in several northern zones of the province are due, at least in part, to lack of competition, but that market power appears limited by spatial arbitrage. In one zone characterized by monopsony, we estimate bids are shaded below their true valuation by $12.56/m3, which approximates the calculated transportation costs ($14.90/m3) to an adjacent more competitive zone. Furthermore, the significance of the inverse mills ratio suggests that ordinary least-squares regression leads to biased estimates. Our findings have policy implications for the future development and use of transaction evidence appraisal models as a potential solution to the long-standing softwood lumber trade dispute.

If America Had Canada's Stumpage System - Henry Spelter (Forest Science, 2006)
The North American lumber market is integrated and, under normal conditions, provides unhindered access to all suppliers. North American log markets, in contrast, function on different principles: in one principle, a profit allowance for the wood processor plays a role in timber pricing, whereas in the other it is a byproduct of the give-and-take of arm's length market negotiations. Under the first system, markets are characterized by high elasticities of price transmission and, at times of market weakness, by low elasticities of product supply. Under the second system, the opposite of these benchmarks prevails. This can result in asymmetric supply responses in weak markets, to the detriment of U.S. producers. Whether this is a subsidy in the sense of conferring a direct financial contribution by the government or merely a more efficient pricing mechanism is beclouded by the dearth of market-based transactions. The challenge in the lumber dispute then is to devise a system of pricing in Canada that is more transparent in regard to the underlying valuation of timber.

Comparative Views of Different Stumpage Pricing Systems: Canada and the United States - Roger A. Sedjo (Forest Science, 2006)
Canada and the United States have many similarities, but major differences in the ownership and tenure of forestlands. These differences generate substantial differences in the way stumpage prices are determined in the two countries. These differences, including the argument that the absence of stumpages markets results in the de facto subsidization of Canadian stumpage prices, are used to justify the host of US trade restrictions on Canadian softwood lumber imports. This article examines the differences in the tenure systems. It cites the arguments commonly given in the dispute and draws out the implications of these systems on softwood resource prices. It discusses some studies, and alternative markets systems, currently under discussion to addresses the criticisms of the Canadian system and critiques one of the major proposals.

Canada–U.S. Softwood Lumber Trade Revisited: Substitution Bias in the Context of a Spatial Price Equilibrium Framework - Anthony Mogus; Brad Stennes; G. Cornelis van Kooten (Forest Science, 2006)
Softwood lumber trade between Canada and the United States has been characterized by various trade restrictions. Many studies have attempted to quantify the effects of such sanctions, modeling softwood lumber as a single, homogenous commodity, although recent research suggests that this may be a misleading assumption because softwood lumber products vary. In this article, we address the problem of “substitution bias” in estimates of the effects of trade restricting policies. A spatial price equilibrium model is used to examine the effects of import duties on Canadian lumber, comparing these with the effects of an export tax and quota. By controlling for substitution bias, our estimates indicate that a larger share of the tariff burden is placed on U.S. consumers, with Canadian producers suffering less injury compared to estimates based on the traditional assumption of a homogenous product. In addition, by comparing the net impact associated with the alternative policy regimes, a policy equivalence is found. Results suggest that the short-run impact of a trade restriction is largely independent of the policy regime incorporated, with the collection of quota rents or tax revenues determining overall winners and losers.

A Legal History of the Softwood Lumber Dispute (in a Nutshell) - Kevin C. Kennedy (Forest Science, 2006)
In every close economic relationship, trade frictions will inevitably occur. The trade relationship between the United States and Canada is no exception. The two-decade long, Canada–U.S. softwood lumber dispute undoubtedly has been the most prominent, if not the most irritating, trade friction of all. The heart of the dispute is the different views in Canada and the United States as to what constitutes a countervailable government subsidy and the proper methodology for determining the amount of such a subsidy when one is found to exist. In the latest round in the softwood lumber dispute, Softwood Lumber IV, Canada and the United States have engaged in a series of parallel dispute settlement proceedings under North American Free Trade Agreement (NAFTA) and at the World Trade Organization. Canada insists that it has won the latest softwood lumber dispute by virtue of an Aug. 2005 decision by a NAFTA Extraordinary Challenge Committee. The United States is equally insistent that the matter remains open by virtue of the International Trade Commission (ITC)s injury determination issued in 2004. With both sides in the Softwood Lumber dispute taking a hard line, such an environment is hardly conducive to the negotiation of a mutually agreeable settlement between the parties. A negotiated resolution of a legal dispute is always better than a litigated one.

Incidence of the 1996 U.S.–Canada Softwood Lumber Agreement among Landowners, Loggers, and Lumber Manufacturers in the U.S. South - Yanshu Li; Daowei Zhang (Forest Science, 2006)
A framework was developed to estimate the welfare incidence of the 1996 U.S.–Canada Softwood Lumber Agreement among producers in two-processing-stage markets—timberland owners, loggers, and lumber manufacturers—in the U.S. South. Timberland owners are the largest beneficiary whereas lumber manufacturers are the second and loggers the least. Empirically, without considering substitution effects among production inputs, timberland owners have 47.4% of total incremental producer surplus, whereas lumber manufacturers have 39.4% and loggers 13.2%. When the substitution effects are considered, timberland owners gain slightly less whereas lumber manufacturers and loggers gain slightly more.

The Law of One Price in the North American Softwood Lumber Markets - Chander Shahi; Shashi Kant; Feng'e Yang (Forest Science, 2006)
The existence of the Law of One Price (LOP) in the North American (10 regional) markets for aggregate softwood lumber and homogeneous softwood lumber products is tested using the Johansen co-integration test and monthly price data for the Softwood Lumber Agreement (SLA) (1996–2001) period and the post-SLA (2001–2004) period. For the aggregate softwood lumber market, the LOP exists neither in the North American aggregate market nor in any combination of one regional market of Canada and all the five regional markets of the United States, nor in one regional market of the United States and all five regional markets of Canada; however, some of the regional markets are co-integrated. The regional markets of homogeneous softwood products in the two countries are co-integrated during both the SLA and post-SLA period. Further studies are essential to understand the difference between the aggregated and homogeneous softwood products market co-integration and to develop a comprehensive and comparative perspective of the Canadian and the US softwood lumber markets.

Market Performance of the Government-Controlled but Market-Based Stumpage System of Ontario - Feng'e Yang; Shashi Kant; Chander Shahi (Forest Science, 2006)
The market performance of the government-controlled stumpage system of Ontario is investigated by examining the relationships between the stumpage prices and the market prices of end products (lumber, composites, and pulp) produced from standing timber, using monthly data from June 1995 to Feb. 2005. The long-run equilibrium relationship between the stumpage price and the relevant market price is tested using Johansen's multivariate co-integration approach. In addition, the Granger-causality between the stumpage price and the relevant market price is also analyzed. Test results indicate that the Ontario stumpage system is working well with respect to the stumpage prices of SPF (spruce, pine, fir) for softwood lumber and pulp, while there is a need for changes and modifications in terms of revising different parameters of the system with respect to stumpage prices of SPF for composites, and stumpage prices of red pine and white pine timber for lumber. Test results are inconclusive for the stumpage price of red pine and white pine for composites.

U.S.–Canada Softwood Lumber Trade: Measuring the Market and Welfare Impacts of Restrictions - Jungho Baek; Runsheng Yin (Forest Science, 2006)
The U.S.–Canada softwood lumber trade dispute is the largest and most contentious one between the two countries. Using a simultaneous system of equations and a vector auto-regression model, and quarterly data for over the last two decades, this article assesses the impacts of the Memorandum of Understanding (MOU) and Softwood Lumber Agreement (SLA). We find that the MOU causes Canadian exports to drop by 8.4–9% during 1986:4–1991:3, which in turn pushes up the U.S. production by 3%. But it does not lead to higher lumber prices. The SLA does not have any significant impacts on the lumber market during 1996:2–2001:1. In addition, the price elasticities of domestic and Canadian export supply are smaller than those commonly used in evaluating the gains and losses of the U.S. restrictions, whereas such factors as exchange rates, housing starts, and log prices have played major roles in shaping the lumber markets. Combining the modest market impacts and smaller price elasticities, we obtain only moderate welfare consequences of the trade restrictions.

Impact of Globalization and Policy Change on United States Softwood Lumber Trade - Qing Xiang; Runsheng Yin (Forest Science, 2006)
To examine the effects of global economic integration, public policy, and other factors on US softwood lumber trade, a demand and supply system for both exports and imports is estimated with panel data sets. We find that the combined impact of trading price and exchange rate before 2003 has made foreign lumber products much cheaper than those manufactured domestically. Furthermore, domestic economic conditions and production capacity strongly affect the exports and imports of both the United States and its trade partners. Also, the US federal harvest reduction policy and the Asian financial crisis influenced both export and import markets. All of these suggest the need for more integrated market analysis and strategic business thinking.

An Editorial Introduction - Runsheng Yin (Forest Science, 2006)

Consequences of Neglecting National Product Differentiation in Assessing the Impact of U.S.–Canada Softwood Lumber Disputes - Jianbang Gan (Forest Science, 2006)
This study, using the Armington approach, analyzes the consequences of omitting national product differentiation on the impact assessment of U.S.–Canada softwood lumber disputes. Omitting national product differentiation is found to cause differences in the estimated impacts ranging from a 38% underestimation to a 340% overestimation under the quantity-based Canadian export tax, and from a 61.5% underestimation to a 413% overestimation under the value-based (ad valorem) U.S. import tariff. Demonstrated as an approach to alleviating the biases, a computable general equilibrium model is developed to simulate the impacts of the 1996 Softwood Lumber Agreement (SLA) and the countervailing duty (CVD) and anti-dumping duty (AD) imposed under the current round of the dispute. The SLA and the CVD and AD seem more likely to cause the redistribution of welfare than to improve the market share of U.S. domestic softwood lumber. The CVD and AD would be more beneficial to the U.S. in terms of overall welfare but causing greater distortions in both the U.S. and Canada than the SLA.

Regional Stem Profile Model for Cross-Border Comparisons of Harvested Red Pine ( Pinus resinosa Ait.) in Ontario and Michigan - W.T. Zakrzewski; D.W. MacFarlane (Forest Science, 2006)
In recent years, considerable attention has been paid to the problem of increasing the comparability of wood valuation across different markets (e.g., stumpage prices), highlighted in the ongoing softwood lumber dispute between the United States and Canada. One major thrust is toward standardizing measurement systems across markets such that volume estimation is more consistent and versatile. As part of the Great Lakes Stem Profile Modeling Project, established to improve the local timber production process and to enable cross-border comparisons of timber volumes, here we present results of a fitting taper (stem profile) model for red pine (Pinus resinosa Ait.) growing in Michigan and Ontario, Canada. Red pine is an important commercial species in both regions. We developed a joint stem profile model that predicts individual tree volume for red pine in Michigan and Ontario with a standard deviation (SD) of error of 10%, demonstrating the feasibility of providing regionally valid stem profile models for major commercial tree species. The stem profile model was fitted as a system of simultaneous equations using a three-stage least-squares regression method. Predictions were evaluated using an equivalence test. We believe that developing statistically and legally defensible estimates of timber product volume across political borders, as exemplified by the regional stem profile model presented here, will improve communication among the trade partners, such as the United States and Canada, by reducing uncertainty created by a lack of comparable estimates.

Plant Species Diversity in a Managed Forest Landscape Composed of Larix kaempferi Plantations and Abandoned Coppice Forests in Central Japan - Takuo Nagaike; Atsuko Hayashi; Masako Kubo; Midori Abe; Nobumasa Arai (Forest Science, 2006)
To evaluate the role of each forest type and stand in an intensively managed forest landscape in terms of vascular plant species diversity, we studied a landscape composed mainly of Larix kaempferi plantations with different stand ages and secondary broad-leaved abandoned coppice forests in central Japan, which were both codominant in the study landscape. All species diversity indices were significantly higher in plantations than in secondary forests. In the detrended correspondence analysis diagram, the younger plantations were distributed far from the older plantations, and the older plantations were located close to broad-leaved secondary forests. The relative frequency of occurrence and number of weed species were both negatively correlated with stand age for plantations, while the number of species with bird-dispersed seeds was positively correlated. Therefore, these changes along the stand-age gradient for specific ecological attributes of species created the similarity in community composition found between older plantations and secondary forests. Because the relative frequency of occurrence and number of tall-tree species and the relative frequency of species with bird-dispersed seeds were significantly higher in secondary forests than in plantations, restoring these species in plantations would likely be a long process.

A Functional Comparison of Productivity in Even-Aged and Multiaged Stands: A Synthesis for Pinus ponderosa - Kevin L. O’Hara; Linda M. Nagel (Forest Science, 2006)
The relative productivity of even-aged and uneven-aged or multiaged stands is a frequently debated topic in silviculture and forestry. Nearly all previous comparisons have been empirical growth studies, simulations of stand growth, or economic analyses based on differences in stem volume production. Both even-aged and multiaged systems are highly variable and the large number of variables and assumptions makes any comparisons difficult. In this review, a series of studies in ponderosa pine are synthesized to develop a more functional understanding of the relative stemwood productivity of these variable stand structures. Multiaged ponderosa pine stands were either as efficient or slightly more efficient at converting light energy to volume growth than even-aged stands. Even-aged stands appear to experience a higher level of mid-summer water stress than multiaged stands. This finding suggests reduced photosynthesis in even-aged stands and a possible cause for a slightly lower level of productivity in even-aged stands. However, differences in productivity are likely insignificant in comparison to the wide variations in even-aged and multiaged structures and differences caused by the operations necessary to maintain these structures. As ponderosa pine systems are primarily water-limited, these results may not apply to more light-limited systems.

Bond, M.L., M.E. Seamans, and R.J. Gutiérrez. 2004. Modeling nesting habitat selection of California spotted owls ( Strix occidentalis occidentalis ) in the Central Sierra Nevada using standard forest inventory metrics (Forest Science, 2006)

Mehtätalo, L. 2005. Localizing a predicted diameter distribution using sample information (Forest Science, 2006)

Restoration of Boreal and Temperate Forests (Forest Science, 2006)

Alternatives to Incorporate Uncertainty and Risk Attitude in Multicriteria Evaluation of Forest Plans - Pekka Leskinen; Jari Viitanen; Annika Kangas; Jyrki Kangas (Forest Science, 2006)
This article studies alternative possibilities to incorporate uncertainty and risk attitude into multicriteria forest planning calculations. The interest is in studying the uncertainties involved in forest owner’s subjective preferences, but the presented approach could be applied also more generally with measurement and modeling errors concerning forest inventory and forecasting, for example. The models applied are based on ratio scale pairwise comparisons of decision elements and their statistical regression analysis, which enables versatile possibilities to incorporate the uncertainty into decisionmaking. In traditional statistical inference, uncertainty is not used directly as a decision criterion that would be required to include risk attitude. However, the statistical approach can be used, for example, to derive pairwise winning probabilities for forest plans beating each other and rank probabilities for forest plans for attaining a given rank. Several types of indices can be derived from these probabilities enabling the incorporation of risk attitude, but a more promising approach was to reduce the decisionmaking problem to contain mean and SD of the utility distributions for each forest plan and provide them as decision support to the forest owner. The approach is based on classical mean-variance utility in portfolio theory. Also, weighted average of certain percentiles of the utility distributions or weighted average of rank probabilities have their advantages.

Transpiration and Canopy Stomatal Conductance of 5-Year-Old Loblolly Pine in Response to Intensive Management - Lisa J. Samuelson; Thomas A. Stokes (Forest Science, 2006)
The influence of weed control only (W) versus weed control plus irrigation (WI) and weed control plus irrigation and fertigation (WIF) on canopy stomatal conductance (G S) and transpiration expressed on a ground (E) and leaf area (E L) basis was examined over 1 year in 5-year-old loblolly pine (Pinus taeda L.) to determine whether increased leaf area index (L) in response to intensive silviculture resulted in regulation of G S, whole-tree hydraulic conductance per unit sapwood area (G), or the ratio of transpiring leaf area to conducting sapwood area (A L:A S) to minimize the gradient in water potential from soil to leaf (ΔΨ). Values of E were as high as 3.9 mm d−1 and increased from a total of 357 mm in the W treatment to 529 and 565 mm in the WI and WIF treatments, respectively. Values of E L did not vary with treatment and were, on average, 0.8 mm d−1 in summer and 0.4 mm d−1 in winter. Increasing management intensity increased L by as much as 76% and sapwood area up to 68%, but had no influence on ΔΨ G, G S, or leaf specific hydraulic conductance. High L values realized by intensive management resulted in regulation of A L:A S to maintain ΔΨ with increasing canopy development.

Evaluation of Selfing Effects on Western Redcedar Growth and Yield in Operational Plantations Using the Tree and Stand Simulator (TASS) - Tongli Wang; John H. Russell (Forest Science, 2006)
Seed lots of western redcedar (Thuja plicata) from both wild stands and seed orchards contain a relatively large proportion of self-pollinated seeds compared to other tree species. Selfed seeds do not exhibit early inbreeding depression, and thus have the same probability of producing acceptable seedlings for field planting as outcrossed ones. However, selfed trees show, on average, about 10% reduction in 9-year height after outplanting. To evaluate the potential negative effects of selfing on productivity at harvest, growth and yield of stands comprising selfs were simulated using TASS (tree and stand simulator) with various planting sites and initial planting densities in this study. Height distributions of selfed and outcrossed individuals were also compared and modeled, which provided a solid basis for accurate TASS simulations and some inside view of selfing in this species. Our results indicate that effects of selfing are smaller on stand final productivity (8% on average) than on 9-year-young trees due to natural selection (competition) against slower-growing trees after crown closure, resulting in more selfs being purged than outcrossed trees. Using better planting sites with higher initial planting densities can substantially intensify the selection and reduce the negative effects of selfing on final productivity.

Timber Harvesting Margins in the Southern United States: A Temporal and Spatial Analysis - Changyou Sun; Daowei Zhang (Forest Science, 2006)
This study focuses on the logging sector by analyzing timber harvesting margins in the southern United States between 1977 and 2001. The real growth rate of harvesting margins has been negative for pine pulpwood, while positive for pine sawtimber, hardwood pulpwood, and hardwood sawtimber. Harvesting margins for pulpwood are more stable over time and more integrated spatially when compared with those for sawtimber. There is no perfect integration in the logging sector by timber product and no individual state is found to lead the logging service market. The revealed patterns are explained in terms of changing demand for forest products and forest industry structure.

Flight Periodicities, Phoresy Rates, and Levels of Pseudopityophthorus minutissimus Branch Colonization in Oak Wilt Centers - Angie K. Ambourn; Jennifer Juzwik; Jordan E. Eggers (Forest Science, 2006)
Oak bark beetles, Pseudopityophthorus minutissimus and P. pruinosus, are considered important vectors of the oak wilt fungus, Ceratocystis fagacearum, in Missouri and Ohio. However, the frequency of the species’ association with diseased oaks in Minnesota and their relative importance in pathogen spread in the state are unclear. Window traps were placed in canopies of recently killed northern pin oaks to determine seasonal flight periodicities of dispersing oak bark beetles and their phoresy (pathogen presence) rates. Branch samples were collected from diseased northern pin and northern red oak canopies in May and Aug., life history data obtained, and oak bark beetles emerging from the branches assayed for the pathogen. Only P. minutissimus was found in the study areas. In 2003, peak flight of P. minutissimus in Minnesota occurred 12 May to 19 May, with 869 beetles being trapped. Dispersing beetles carried viable pathogen propagules at low frequencies (4 to 13 per 1,000) in May and June. Branches of oak wilt-killed trees were commonly colonized by the beetle. More beetles emerged from branch samples collected in May than in Aug., but none yielded C. fagacearum. These results support the hypothesis that the relative importance of P. minutissimus in the overland transmission of the pathogen in red oak species in Minnesota is minor.

The Effectiveness of Different Buffer Widths for Protecting Headwater Stream Temperature in Maine - Ethel Wilkerson; John M. Hagan; Darlene Siegel; Andrew A. Whitman (Forest Science, 2006)
We evaluated the effect of timber harvesting on summer water temperature in first-order headwater streams in western Maine. Fifteen streams were assigned to one of five treatments: (1) clearcutting with no stream buffer; (2) clearcutting with 11-m, partially harvested buffers, both sides; (3) clearcutting with 23-m, partially harvested buffers; (4) partial cuts with no designated buffer; and (5) unharvested controls. Over a 3-year period we measured summer water temperature hourly before and after harvesting, above and below the harvest zone. Streams without a buffer showed the greatest increase in mean weekly maximum temperatures following harvesting (1.4–4.4°C). Streams with an 11-m buffer showed minor, but not significant, increases (1.0–1.4°C). Streams with a 23-m buffer, partial-harvest treatment, and control streams showed no changes following harvest. The mean weekly maximum temperatures never exceeded the thermal stress limit for brook trout (25°C) in any treatment group. The mean daily temperature fluctuations for streams without buffers increased from 1.5°C/day to 3.8°C/day, while with 11-m buffers fluctuations increased nonsignificantly by 0.5–0.7°C/day. Water temperatures 100 m below the harvest zone in the no-buffer treatment were elevated above preharvest levels. We concluded that water temperature in small headwater streams is protected from the effects of clearcutting by an 11-m buffer (with >60% canopy retention).

Market Orientation, Strategy, and Performance in the Primary Forest Industry - Eric Hansen; Clay Dibrell; Jon Down (Forest Science, 2006)
Over a decade of research on market orientation has produced many insights into the market orientation–performance relationship. More recently, researchers have begun to incorporate other strategic phenomena into their market orientation work. We build on this growing knowledge base by investigating the mediating role of firm strategy on the market orientation-firm performance connection. Findings show that market orientation has a positive impact on all forms of firm strategy (i.e., customer differentiation, product differentiation, channel differentiation, and overall low cost). However, only a channel differentiation strategy in combination with a market orientation produced a positive impact on firm performance. In contrast, a low cost strategy had a positive impact on firm performance in the absence of a market orientation.

Fuzzy Multicriteria Approval Method and its Application to Two Forest Planning Problems - Annika Kangas; Jyrki Kangas; Sanna Laukkanen (Forest Science, 2006)
Many different multicriteria decision aid methods have been used in forestry decision support. When opinions of the general public are considered, methods that are simple to understand and easy to use are required. One such method is multicriteria approval (MA). It is based on approval voting, where the voters have been replaced by criteria. In MA, alternatives are approved or rejected with respect to each voter, i.e., each criterion. In the basic version, the approval threshold is crisp and defined by the system. The varying importance of the criteria is considered using the concept of ordinal dominance. Thus, the importance order of the criteria is needed to make a recommendation. The basic MA approach favors solutions that may be mediocre with respect to all criteria. A crisp approval threshold used in MA may also lead to awkward recommendations. We propose a new method using a concept of fuzzy approval for solving these problems. The fuzzy approval also easily extends to group decision-making problems. Two forestry applications are presented, where the fuzzy version of MA is tested and compared to the results of original MA. The possibilities of using fuzzy approval in forestry decision support are discussed.

Variance Reduction for Sector Sampling - Thomas B. Lynch (Forest Science, 2006)
Variance reduction techniques used in Monte Carlo integration including control variates and importance sampling can use estimated or actual shapes of vegetated land areas to reduce the variance of estimators from sector sampling. The estimated shapes of forested areas could come from maps, aerial photos, or similar sources. Antithetic variates for variance reduction in Monte Carlo integration can be applied to sector sampling without using any estimated shape or map. Sector sampling selects as samples all trees or other vegetation of interest located in randomly chosen sectors that have a vertex at a common point located in the interior of a forested area. Each sector is associated with an angle of fixed magnitude emanating from the interior point. Sector orientation is based on a randomly selected azimuth originating at the interior point that is the vertex for each sector. This technique is well adapted to application on relatively small areas that have irregularly shaped boundaries. Sector sampling can be demonstrated to be unbiased. Unbiasedness holds with angle reduction for adjustment of sample size and with the variance reduction techniques that are proposed. The method is not restricted to application with trees because sector sampling methods could be applied just as well to other vegetation types or any other objects located in the land area of interest.

Dynamic Site Model for Loblolly Pine ( Pinus taeda L.) Plantations in the United States - Ulises Diéguez-Aranda; Harold E. Burkhart; Ralph L. Amateis (Forest Science, 2006)
Data from a large, long-term loblolly pine (Pinus taeda L.) plantation study including 186 permanent sample plots were used to evaluate four dynamic site equations derived with the generalized algebraic difference approach (GADA). All of the equations are base-age invariant and directly estimate height and site index from any height and age. The fittings were done in one stage using the base–age invariant dummy variables method. A first-order autoregressive error structure was used to correct the serial correlation of the longitudinal data used in this study. Cieszewski’s model (Cieszewski, C.J. 2002. Comparing fixed- and variable-base–age site equations having single versus multiple asymptotes. For. Sci. 48:7–23) best described the data.

Inventory Updates and Related Topics: From Special Sampling Techniques to Stochastic Analyses - Chris J. Cieszewski; Mike Strub (Forest Science, 2006)

Modeling Individual-Tree Growth from Data with Highly Irregular Measurement Intervals - Thomas Nord-Larsen (Forest Science, 2006)
Fitting annual tree growth and survival models to data with irregular measurement intervals requires special consideration to the interpolation of the independent variables. This study presents an iterative method for continuously updating individual-tree and stand attributes, using the hypothesized functional form of a system of forward difference equations. Based on data from permanent sample plots, parameter estimates were obtained for three first-order difference equations of diameter and height growth and mortality for European beech in Denmark. One parameter of the individual-tree diameter and height growth models was estimated locally and expresses apparent site quality. The plot-specific parameters of the individual-tree growth models were highly correlated with site index and plot-specific estimates of rate constants from a dominant height growth model. Parameter estimates of individual-tree models based on either of those indicators of site quality allow for a flexible use of the models. The study failed to establish any relation between plot-specific rate constants and soil texture variables. The resulting system of individual-tree models is consistent with tree growth and mortality expected for beech in Denmark.

Analysis of Different Base Models and Methods of Site Model Derivation for Scots Pine - Chris J. Cieszewski; Michał Zasada; Mike Strub (Forest Science, 2006)
Using an example of averaged growth series data of Scots pine (Pinus sylvestris L.), we examine several approaches to site-dependent height-age model derivation. We consider several renowned base models (two-dimensional equations, such as Y = f(t)) and derive from them anamorphic and polymorphic dynamic site equations (three-dimensional site-height-age models, such as Y = f(t, t 0, y 0)) of different complexities. The considered base models were selected previously as suitable for Scots pine in other studies, and are different variations of exponential and fractional functions. We compare all of the base models fit to individual site classes and the derived base-age invariant anamorphic and polymorphic dynamic site equations fit to all sites pooled together. All the fits of site equations to the pooled data from different site productivity series were based on base-age invariant stochastic regressions, in which the global model parameters that are common to all data are estimated simultaneously with the site effects unique for each site productivity series. The results show that: (1) choice of definition describing changes across site qualities may be more important than the choice of base equation defining changes over time; (2) a base model with high cost of deriving self-referencing function may sometimes be better than a base model with low cost of deriving the self-referencing function; and (3) superior base models may not produce superior anamorphic or simple polymorphic site models, but can produce superior advanced polymorphic site models, which can describe the growth patterns in data better than either anamorphic or simple polymorphic models.

Developing Dynamic Site Index Curves for European Beech ( Fagus sylvatica L.) in Denmark - Thomas Nord-Larsen (Forest Science, 2006)
In base-age specific methodologies, assessment of base age and site index may be a problem when developing site curves from repeated measurements on permanent sample plot data. In most cases, such data will not contain measurements at any base age that is common for all the sample plots, and some sort of interpolation or even extrapolation would have to be applied to address this issue. Base-age invariant methodologies pose the desirable property of estimating the curves without prior arbitrary assumptions about values of the site indices. Presented here is the development of such base-age invariant site index curves for European beech (Fagus sylvatica L.) in Denmark, fitted to permanent sample plot data. The developed polymorphic dynamic site equations with variable asymptotes are based on the generalized algebraic difference approach, and the parameters of the model were estimated with correction for first-order serial correlation.

Optimal Regeneration Planning for Old-Growth Forest: Addressing Scientific Uncertainty in Endangered Species Recovery through Adaptive Management - Clinton T. Moore; Michael J. Conroy (Forest Science, 2006)
Stochastic and structural uncertainties about forest dynamics present challenges in the management of ephemeral habitat conditions for endangered forest species. Maintaining critical foraging and breeding habitat for the endangered red-cockaded woodpecker (Picoides borealis) requires an uninterrupted supply of old-growth forest. We constructed and optimized a dynamic forest growth model for the Piedmont National Wildlife Refuge (Georgia, USA) with the objective of perpetuating a maximum stream of old-growth forest habitat. Our model accommodates stochastic disturbances and hardwood succession rates, and uncertainty about model structure. We produced a regeneration policy that was indexed by current forest state and by current weight of evidence among alternative model forms. We used adaptive stochastic dynamic programming, which anticipates that model probabilities, as well as forest states, may change through time, with consequent evolution of the optimal decision for any given forest state. In light of considerable uncertainty about forest dynamics, we analyzed a set of competing models incorporating extreme, but plausible, parameter values. Under any of these models, forest silviculture practices currently recommended for the creation of woodpecker habitat are suboptimal. We endorse fully adaptive approaches to the management of endangered species habitats in which predictive modeling, monitoring, and assessment are tightly linked.

A New Type of Sample Plot that Is Particularly Useful for Sampling Small Clusters of Objects - Kim Iles; Nicholas J. Smith (Forest Science, 2006)
The sampling method presented here uses a new type of plot, with surprising characteristics. Although useful in sampling any grouping of objects, it is illustrated here by correctly sampling small patches of trees remaining after harvest. Small patches are difficult to sample unbiasedly because of the “edge effect𠇍 caused by sampling with fixed or variable plots. By this we do not refer to a biological effect on trees near an edge, but to a common sampling bias that distorts the selection probabilities of those trees. Groups of objects that are small and irregular are very prone to this “edge effect bias𠇍 when using typical sampling systems. “Sector plots𠇍 will allow the user to sample the trees in a small patch, and the method can also be extended to small trees planted outside the patch after harvesting, or to solitary “dispersed𠇍 trees outside the patch but within the harvested area. The method can unbiasedly select sample trees along an irregular border. The method eliminates all bias from edge effect. It can balance the tree selection on opposite sides of the patch, and the pivot point of the plot can be arbitrarily placed by the sampler in any convenient location without introducing any bias to the selection process. This new plot shape might be described as “a constrained angle shape with variable area, randomly oriented around an arbitrary sample point, which selects objects with equal probabilities.𠇍

Applying an Efficient k -Nearest Neighbor Search to Forest Attribute Imputation - Andrew O. Finley; Ronald E. McRoberts; Alan R. Ek (Forest Science, 2006)
This article explores the utility of an efficient nearest neighbor (NN) search algorithm for applications in multisource kNN forest attribute imputation. The search algorithm reduces the number of distance calculations between a given target vector and each reference vector, thereby decreasing the time needed to discover the NN subset. Results of five trials show gains in NN search efficiency ranging from 75 to 98% for k = 1. The search algorithm can be easily incorporated into routines that optimize feature subsets or weights, values of k, distance decomposition coefficients, and mapping.

Horizontal Line Sampling for Riparian Forests without Land Area Estimation - Thomas B. Lynch (Forest Science, 2006)
Sampling forests in riparian areas presents unique difficulties that can be addressed by judicious application of line sampling. Land areas associated with riparian forests often have highly irregular boundaries, making accurate area determination difficult. Therefore, estimators for total amounts of forest attributes that do not depend on land area are desirable. Such estimators can be obtained by using horizontal line sampling from sample lines that are located at random intervals along a straight baseline and which extend entirely through the riparian area of interest. Horizontal line sampling selects sample trees that subtend an angle whose vertex is located on a length of line. This is conceptually similar to Ståhl's transect relascope sampling (Ståhl, G. 1998. Transect relascope sampling—A method for the quantification of course woody debris. For. Sci. 44:58–63), which estimates total amounts of coarse woody debris from lines established at fixed intervals. Use of a control variate or importance sampling based on predicted line length (where available) is suggested as a variance reduction technique. An unbiased estimator for sampling at intervals along the line is suggested. Monte Carlo integration estimates of riparian land area are proposed for estimation of per-unit area quantities. These estimators could be applied to any forested area but appear to be most well suited to long, relatively narrow riparian areas.

Potential of Aerial Image-Based Monoscopic and Multiview Single-Tree Forest Inventory: A Simulation Approach - Ilkka Sakari Korpela; Timo Erkki Tokola (Forest Science, 2006)
Two aerial image-based estimation chains were compared for their potential in the assessment of timber resources. The two chains consisted of two- and three-dimensional image measurements followed by indirect model estimation. The effects of various errors at both the single-tree and stand levels were examined with Monte Carlo simulation. The three-dimensional multiview estimation chain with height measurements of individual trees proved less prone to random and systematic errors than the monoscopic chain. An upper limit of accuracy at the single-tree level is determined mainly by the allometric correlations. Volume estimates of single trees showed estimation accuracies (root-mean-square error, RMSE) of 15–20% and 35–40% in the multiview and monoscopic chains, respectively. This is lower than the accuracy achievable in the field, which is 6%. Image-based single-tree forest inventory is prone to systematic measurement and model errors, and in a simulation for the total effect of error sources, upper estimation accuracies (RMSE) of 15% and 30% for stand volume were computed using full mapping of the stand with the multiview and monoscopic estimation chains, respectively.

Base–Age Invariance Properties of Two Techniques for Estimating the Parameters of Site Index Models - Mike Strub; Chris J. Cieszewski (Forest Science, 2006)
Using eight hypothetical data points (four growth series with two observations each) the difference between two site index curve parameter estimation methods, the base–age invariant stochastic regression approach (BAI) and the method of all base ages (BAA), is illustrated. The anamorphic form of the Schumacher log-transform height–age equation is used for the comparison. The two estimation techniques are equivalent for the linear case of the model but produce different parameter estimates for its nonlinear form. For both linear and nonlinear cases the BAI approach produced a lower root-mean-squared error than the BAA method. Only the BAI approach produced unique estimates for the site-specific parameters of both model forms and both growth series.

Finding the Efficient Frontier of a Bi-Criteria, Spatially Explicit, Harvest Scheduling Problem - Tóth Sándor F.; Marc E. McDill; Stephanie Rebain (Forest Science, 2006)
The effects of cost-sharing and information assistance on nonindustrial private forest owners’ investment in timber stand improvements are analyzed using a two-step estimation method. We use survey data on Finnish nonindustrial private forestland owners’ stand improvements in 1994–1998, including precommercial thinnings, cleaning of seedling stands, and restoration thinnings of juvenile stands. The investment decision is theoretically considered in a two-period model with amenity values. To allow for the joint determination of participation in the cost-sharing program and the decision to invest, a two-step estimation method is used. The predicted probability of using public subsidy from the first-step model is included in the second-step model for the probability or relative extent of stand improvements. For robust inference, quasi-maximum likelihood estimation is applied. Public subsidy, personal assistance, and forest planning expectedly increased the probability of investing. Public subsidy especially had substantial effects on the probability and extent of stand improvements. Besides overcoming the endogeneity of cost-sharing, the two-step approach showed that personal assistance also encourages stand improvements indirectly through its effect on the use of public subsidy.

Detailed Stem Measurements of Standing Trees from Ground-Based Scanning Lidar - Jason G. Henning; Philip J. Radtke (Forest Science, 2006)
A commercially available pan-and-tilt mount laser scanner was used to acquire data for subsequent three-dimensional modeling and measurement of standing forest trees. Methods were developed for identifying trees in range images and co-registering range images acquired from different vantage points. Upper-stem diameters and branch heights derived from the range images were compared to measurements made after the felling of a small number of loblolly pine (Pinus taeda L.) trees. Tree identification assumed bole cross-sections were circular, estimating their geometric centers at successive heights up the stem. Tree center estimates at multiple heights were then used to co-register images made from different vantage points. Co-registration (x, y) errors did not exceed 2.1 cm in any of the 18 pairwise registrations carried out. Results showed excellent agreement (average error < 1 cm) between the lidar-derived diameter estimates and caliper measurements for bole sections below the base of live crown. Less accurate estimates (<2 cm) were obtained for stem heights up to 13 m. Results indicated the potential for accurate assessment of branch or whorl heights using ground-based scanning lidar, with the greatest accuracy likely to be realized for branches near the base of the live crown and below it.

Comparison of Experimental Designs for Clonal Forestry Using Simulated Data - Salvador A. Gezan; Timothy L. White; Dudley A. Huber (Forest Science, 2006)
Various alternatives for the design of clonal field trials in forestry were studied using simulated data to identify “optimal𠇍 or “near-optimal𠇍 scenarios for the estimation of genetic parameters. The simulated field site consisted of a rectangular grid on which 256 clones with 8 ramets each were installed. Estimates of genetic parameters were compared for (1) single-tree and four-tree row plots; (2) several experimental designs (completely randomized, randomized complete block, incomplete blocks of various sizes, and row–column); (3) no mortality versus 257% mortality; and (4) different patterns of environmental variability (only patches, only gradients, and both patches and gradients). Use of single-tree plots, on average, increased the correlations between true and predicted clonal values by 57% over four-tree row plots and increased genetic gain from selection. Starting with a parametric broad-sense heritability (H B 2) of 0.25 for a completely randomized design, the experimental designs resulting in the highest H B 2 were row–column designs for single-tree plots and incomplete blocks with 32 blocks per replication when four-tree row plots were used. These designs increased average heritability 107% and 147% over a randomized complete block design, respectively. The only effect of 257% mortality was an increase in the variability of some variance component estimates.

Application of the Algebraic Difference Approach for Developing Self-Referencing Specific Gravity and Biomass Equations - Lewis Jordan; Ray Souter; Bernard Parresol; Richard F. Daniels (Forest Science, 2006)
Biomass estimation is critical for looking at ecosystem processes and as a measure of stand yield. The density-integral approach allows for coincident estimation of stem profile and biomass. The algebraic difference approach (ADA) permits the derivation of dynamic or nonstatic functions. In this study we applied the ADA to develop a self-referencing specific gravity function and biomass function as part of a density-integral system composed of taper, volume, specific gravity, and biomass functions. This was compared to base systems of similar equations that did not have the self-referencing parameter specifications. Systems of equations were fit using nonlinear, seemingly unrelated regressions with nonlinear cross-equation constraints to account for contemporaneous correlations in the data. Results suggest that correct volume determination is more critical than specific gravity for accurate biomass estimates. The goodness-of-fit statistics clearly show that the self-referencing system provided a better fit than the base system.

Corrections for Cluster-Plot Slop - Harry T. Valentine; Mark J. Ducey; Jeffrey H. Gove; Adrian Lanz; David L.R. Affleck (Forest Science, 2006)
Cluster-plot designs, including the design used by the Forest Inventory and Analysis program of the USDA Forest Service (FIA), are attended by a complicated boundary slopover problem. Slopover occurs where inclusion zones of objects of interest cross the boundary of the area of interest. The dispersed nature of inclusion zones that arise from the use of cluster plots precludes the use of most of the slopover-correction methods that apply to solitary plots. One exception is the walkthrough method, which corrects for slopover bias in radially symmetric cluster-plot designs. In this article, we provide a modification of the walkthrough method, the “walkabout method,𠇍 which is applicable to some asymmetric cluster-plot designs, such as the one used by FIA. We also present two general correction methods, the “vectorwalk method𠇍 and the “reflection method,𠇍 both of which are applicable to cluster-plot designs with satellite subplots arranged in a regular or irregular pattern. The reflection method has two sets of protocols, one that applies to radially symmetric designs and to asymmetric designs with random orientation; the other set applies to asymmetric designs with fixed orientation. Both the vectorwalk and reflection methods incorporate the walkthrough method on a subplot-by-subplot basis. All four methods correct for slopover bias for straight or curved boundaries, and where work outside the tract is impossible.

A Multilevel Approach to Individual Tree Survival Prediction - Charles E. Rose; Daniel B. Hall; Barry D. Shiver; Michael L. Clutter; Bruce Borders (Forest Science, 2006)
Traditionally, modeling of permanent plot individual tree survival has not considered the multiple sources of heterogeneity and correlation that may arise due to the multilevel data structure inherent in the design (e.g., clustering of trees within a plot). Permanent plots are sampled periodically; therefore, data are interval-censored because it is only known that a tree died between two successive measurement occasions. Here, we adopt the complementary log–log (CLL) function for modeling permanent plot interval-censored individual tree survival data. The CLL function is derived directly from the likelihood function of a fully specified statistical model that accounts for interval censoring. In addition, our CLL model considers silvicultural treatment effects on survival. Our data are from young permanent plot loblolly pine plantations that have been measured annually beginning at age 1 year. Each plot was randomly assigned one of four cultural treatments:control (C), herbicide (H), fertilization (F), and herbicide and fertilization (HF). Here we extend the individual tree survival CLL model to allow for trees within a plot and plot level random effects. We demonstrate individual tree survival predictions with and without the inclusion of random effects.

Does Faustmann Rotation Apply to Fully Regulated Forests? - Olli Tahvonen; Esa-Jussi Viitala (Forest Science, 2006)
Forest economics literature contains two lines of research in which the Faustmann rotation is taken to be invalid for continuous harvesting, i.e., for normal or fully regulated forests. As alternatives, a “marginal model for divisible forest capital𠇍 and a “regular profit model for timber production𠇍 have been proposed and applied. In contrast, recent forest economics has provided vast evidence that the Faustmann rotation is the long-term stationary state in rotation models with multiple age classes. In this article, we attempt to clear up this contradiction in the literature by showing that the two approaches deviating from the Faustmann approach yield the same rotation period. The deviations from the Faustmann approach are because the models are based on incorrect formulas for the value of a normal forest.

Cost-Sharing and Private Timber Stand Improvements: A Two-Step Estimation Approach - Ville Ovaskainen; Harri Hänninen; Jarmo Mikkola; Emmi Lehtonen (Forest Science, 2006)
The effects of cost-sharing and information assistance on nonindustrial private forest owners’ investment in timber stand improvements are analyzed using a two-step estimation method. We use survey data on Finnish nonindustrial private forestland owners’ stand improvements in 1994–1998, including precommercial thinnings, cleaning of seedling stands, and restoration thinnings of juvenile stands. The investment decision is theoretically considered in a two-period model with amenity values. To allow for the joint determination of participation in the cost-sharing program and the decision to invest, a two-step estimation method is used. The predicted probability of using public subsidy from the first-step model is included in the second-step model for the probability or relative extent of stand improvements. For robust inference, quasi-maximum likelihood estimation is applied. Public subsidy, personal assistance, and forest planning expectedly increased the probability of investing. Public subsidy especially had substantial effects on the probability and extent of stand improvements. Besides overcoming the endogeneity of cost-sharing, the two-step approach showed that personal assistance also encourages stand improvements indirectly through its effect on the use of public subsidy.

Substitutability between US Domestic and Imported Forest Products: The Armington Approach - Jianbang Gan (Forest Science, 2006)
This article estimates the Armington elasticities of substitution between US domestic and imported forest products. The results indicate that US domestic and foreign forest products are far from perfect substitutes for each other. The low substitutability calls into question the effectiveness of import restrictions that alter the relative price between domestic output and imports and the trade impact assessments that impose the law of one price. The degree of substitutability is higher in the long run than in the short run and varies across product aggregation levels. The elasticity estimates, though remaining relatively stable for most forest products, show an increase since the late 1980s for the overall forest product, implying that US domestic and imported forest products have, in general, become more substitutable over time.

Interest in Cross-Boundary Cooperation: Identification of Distinct Types of Private Forest Owners - Andrew O. Finely; David B. Kittredge; Thomas H. Stevens; Charles M. Schweik; Donald C. Dennis (Forest Science, 2006)
This article presents quantitative results from a study that evaluated private forest (PF) owner interest in cross-boundary cooperation. The intent was to reveal subgroups, referred to here as segments, of PF owners that align with different forms and levels of cooperative activities. Segmentation analysis used 783 mail-back surveys from Franklin County, Massachusetts, PF owners in spring 2002. The analysis indicates that there are four segments of PF owners in Franklin County, each maintaining a distinct level of interest in proposed forms of cooperation. Two segments define positive interest in cooperation (General Cooperators, 27%; Conservation Cooperators, 21%), and the other two represent apathy (Neutralists, 27%), and disinterest (Non-Cooperators, 24%). Furthermore, each segment presents a unique profile of items and scales that measure personal values and attitudes about cross-boundary cooperation and socioeconomic and demographic characteristics. Segment profiles show a strong association between interest in cooperation and profiling variables such as age, affluence, personal values, and attitudes. By identifying the specific needs and wants among PF owners, these findings can help in the development of responsive initiatives to promote cross-boundary cooperation in Franklin County. Furthermore, the outlined segmentation analysis could aid PF owner studies identify and describe key segments and determine interest in cross-boundary cooperation.

BOOK REVIEWS: Valuing Agroforestry Systems: Methods and Applications - Martin K. Luckert (Forest Science, 2005)
Agroforestry has long been touted as a management approach with potential for gaining synergies between agricultural and forest production. A staple approach in developing-country situations, agroforestry systems are increasingly being considered in developed-country settings. However, socioeconomic analyses of agroforestry systems have long lagged behind natural science contributions. This volume, the second in the series “Advances in Agroforestry,” makes a significant step in promoting the social science importance of agroforestry. The editors have assembled a nice collection of studies regarding the valuation of agroforestry systems around the world, encompassing developing and developed country settings. The approaches used arise largely from an economics disciplinary background, but there is much in here of interest to a broader, multidisciplinary audience.

Litterfall Dynamics of an Evergreen Broadleaf Forest and a Pine Forest in the Subtropical Region of China - Zhi An Li; Bi Zou; Han-ping Xia; Hai Ren; Jiang-ming Mo; Hong Weng (Forest Science, 2005)
Monthly litterfall was monitored over a 10-year period from an evergreen broadleaf forest (EBF) and a pine forest (PF) in subtropical South China. During this period, litter was also collected bimonthly from the forest floor for 2 years. Total annual litterfall in EBF fluctuated around 9 Mg ha−1 with leaves, branches, and miscellanea accounting for 52.5%, 22.2%, and 25.3%, respectively. Total annual litterfall alternated between high and low values in consecutive years. Storms and pest outbreaks were responsible for most of the peaks in both monthly and annual litterfall. Litter from each of 43 species was recorded, but 9 species contributed about 85% of total litterfall. Dominant species shed their leaves in a more regular pattern with peaks mainly from Jan. to Mar. Pine forest (Pinus massoniana) produced much less litterfall than EBF, with a mean of 2.7 Mg ha−1. Here, leaves accounted for 73.2% of total litterfall, branches only 11.4%, and miscellanea 15.4%. Litter on the ground amounted to 5.2 Mg ha−1 in EBF and 2.9 Mg ha−1 in PF. The results show that this climax forest has much higher litterfall and forest floor mass than the pine forest, and litterfall is rather stable with regard to annual variation. FOR. SCI. 51(6):608–615.

Rhizobacteria Isolated from Loblolly Pine Seedlings Mediate Growth-Promotion of Greenhouse-Grown Loblolly, Slash, and Longleaf Pine Seedlings - S. A. Enebak (Forest Science, 2005)
Loblolly (Pinus taeda L.), slash (Pinus elliottii Engelm.), and longleaf pine (Pinus palustris Mill.) seeds were inoculated in the greenhouse with rhizobacteria recovered from 4-month-old bareroot loblolly pine seedlings. Emergence and seedling densities were determined at 3- and 8-week intervals after sowing, respectively, with root and shoot biomass measured at 12 weeks. All bacterial strains significantly increased the speed of seedling emergence relative to untreated loblolly and slash pine seeds, while five strains significantly slowed longleaf germination. For loblolly and slash pine, there were no differences in percentage germination when comparing treated and untreated seed. However, all bacterial strains significantly reduced longleaf germination over nontreated seed. Treatment with rhizobacteria had significant positive and negative effects on seedling growth and biomass, depending on the tree species and bacteria isolate used. Five of the eight bacterial isolates tested increased shoot length of loblolly pine seedlings, whereas one strain increased above- and belowground biomass. Slash pine seedlings experienced growth increases with three bacterial strains. However, two bacterial strains, ALA-41G and ALA-54G, resulted in shorter slash pine shoots. Only strain ALA-3G increased shoot biomass of longleaf pine over nontreated longleaf seed. Increased seedling emergence and growth promotion by rhizobacteria collected from Pinus sp. is a potential useful tool for management of these forest species. The effect may be species-specific and the use of bacteria in forest nurseries for growth promotion will need to take this into account. FOR. SCI. 51(6):541–545.

Provenance Trials of Ponderosa Pine in Northern California - Jay H. Kitzmiller (Forest Science, 2005)
Growth of 17 ponderosa pine populations transferred within the southern Cascades–Sierra Nevada ranges were tested for 19 years on two contrasting sites, Cherry Hill (CH) and Peanut Springs (PS). Seven additional southern Sierra populations were tested at PS. Results provide guidance to forest managers seeking to reforest ponderosa pine after large wildfires or to improve productivity of plantations. PS represented warm, moist, lower mixed-conifer sites in the central Sierra. CH represented colder, drier climates at the southern limit of the Cascades in upper elevation mixed-conifer. High inherent site productivity at PS was reduced by topsoil displacement and brush competition for moisture and/or nutrients. Contrasting magnitudes and patterns of growth among provenances were expressed between sites. The local provenance at PS outgrew more distant sources by 12 to 74%. However, high elevation, nonlocal Sierra sources grew best at CH, where volume decreased with source latitude and increased with source elevation. All sources had stockier form at CH. In both tests, Sierra sources outgrew and were stockier than Cascade sources; stockiness increased with source elevation. Current results at CH support matching provenance elevation with site, using southern sources. Results at PS strongly support the use of local seed, with allowance for transferring seed to adjacent zones. FOR. SCI. 51(6):595–607.

Estimating Supply Elasticity for Disaggregated Paper Products: A Primal Approach - Roger Brown; Daowei Zhang (Forest Science, 2005)
Most existing elasticity estimates for the pulp and paper industry are based on aggregate products (e.g., total paper, paperboard, or paper except newsprint). Using United States data, we present and evaluate econometric output supply models for four relatively disaggregated paper products: newsprint paper (NP), printing/writing paper (PWP), tissue paper (TP), and packaging paper (PP). Sample periods vary from 14 years for PP (1987–2001) to 20 years for NP and PWP (1981–2001). Each paper type is specified using a two-stage least squares geometric distributed lag model in log–log form using monthly data. Estimated long-run (short-run) output price elasticities are 2.75 (0.69) for NP, 2.45 (1.07) for PWP, 1.77 (1.77) for TP, and 0.41 (0.24) for PP. Input demand elasticities for capital, wood fiber, labor, electricity, and wastepaper are also estimated for each paper type. FOR. SCI. 51(6):570–577.

Parsimonious and Completely Compatible Taper, Total, and Merchantable Volume Models - Lewis Jordan; Kenneth Berenhaut; Ray Souter; Richard F. Daniels (Forest Science, 2005)
A parsimonious and compatible system of taper, total, and merchantable volume equations sharing a common vector of three parameter estimates was derived from Clark and Saucier's (1990) volume ratio model. Clark and Saucier's model expresses volume inside bark as a function of outside bark diameter and is itself not compatible with the derived taper equation. To ensure compatibility, models were fit to express volume outside bark as functions of diameter outside bark. By constraining the limits of integration of the taper function to go from the tip to groundline diameter, a completely compatible system of taper, total, and merchantable volume equations were developed. Systems of equations were fit using nonlinear seemingly unrelated regressions with nonlinear cross-equation constraints to account for contemporaneous correlations in the data. The system fit was found to account for at least 96% of the variation in diameter outside bark, total, and merchantable outside bark volume. FOR. SCI. 51(6):578–584.

Tropical Forest Measurement by Interferometric Height Modeling and P-Band Radar Backscatter - Till Neeff; Luciano Vieira Dutra; João Roberto dos Santos; Corina da Costa Freitas; Luciana Spinelli Araujo (Forest Science, 2005)
A new approach to tropical forest biomass monitoring with airborne interferometric X and P-band synthetic aperture radar (SAR) data is presented. Forest height, basal area, and aboveground biomass are modeled from remote sensing data for a study site in the Brazilian Amazon. Radar data quality has improved: A novel digital model of vegetation height from X- and P-band interferometry is available along with the usual P-band backscatter information. The digital vegetation height model is derived from the interferometric surface models of the ground (from P-band) and the forest canopy (from X-band). The difference between the surface models is called “interferometric height,” and is used as a measure of vegetation height. Interferometric height is shown to relate to a subset of the forest trees that changes according to the forest successional stages. The suitability of radar backscatter and interferometric height as a means for forest and biomass monitoring was explored by relating forest parameters as measured in the field to remote sensing data. Basal area and biomass were related to radar backscatter with limited precision of r2 = 0.19 and r2 = 0.34, respectively. Mean forest height is shown to relate to interferometric height with good precision (r2 = 0.83, RMSE = 4.1 m). A statistical model for forest biomass as a function of both P-band backscatter and interferometric height information not only arrives at high values of precision (with r2 = 0.89 and a RMSE from cross-validation of only 46.1 t/ha), but also overcomes the well-known issue of backscatter saturation. This research shows that tropical forest biomass can be quantified and mapped over large areas for a range of forest structures with reasonably tight and similar errors. FOR. SCI. 51(6):585–594.

Production Efficiency and Radiation Use Efficiency of Four Tree Species Receiving Irrigation and Fertilization - Christopher B. Allen; Rodney E. Will; Marshall A. Jacobson (Forest Science, 2005)
To determine the effect of resource availability on efficiency of stemwood production, we calculated radiation use efficiency (Εstem = stem production/photosynthetically active radiation [PAR] interception) and production efficiency (PEstem = stem production/leaf area index [LAI]) from measurements of LAI, intercepted photosynthetically active radiation (IPAR), and stem production on stands of Pinus taeda, Pinus elliottii, Liquidambar styraciflua, and Platanus occidentalis during the sixth growing season. Treatments were control, irrigation only, and irrigation plus 57, 85, or 114 kg N ha−1 y−1. Compared to the control, irrigation plus 85 kg N ha−1 increased stem production: 8.7–15.0 Mg ha−1 y−1 (loblolly), 6.0–10.7 Mg ha−1 y−1 (slash), 1.2–12.8 Mg ha−1 y−1 (sweetgum), and 0.5–9.6 Mg ha−1 y−1 (sycamore). Annual PAR capture and LAI were correlated with stem production (r2 = 0.80, r2 = 0.66, respectively, average of 4 species). Fertilization and irrigation increased Εstem and PEstem for sycamore, whereas only fertilization increased efficiencies for sweetgum. Irrigation increased PEstem for the pines. Foliar [N], often a surrogate for photosynthetic efficiency, was positively correlated with both efficiency variables for the hardwoods (r2 from 0.65 to 0.79). For the pines, canopy size was the primary growth determinant. FOR. SCI. 51(6):556–569.

Foliar δ13C and δ15N Response of Lodgepole Pine and Douglas-Fir Seedlings to Soil Compaction and Forest Floor Removal - Woo-Jung Choi; Scott X. Chang; Michael P. Curran; Hee-Myong Ro; Mohammed Kamaluddin; Janusz J. Zwiazek (Forest Science, 2005)
The effects of soil compaction, forest floor (FF) removal, and rehabilitation treatments on foliar δ13C and δ15N of lodgepole pine (Pinus contorta) and Douglas-fir (Pseudotsuga menziesii) were studied on a calcareous soil. Regardless of soil compaction, FF removal (which reduces soil water potential) resulted in less negative foliar δ13C values of lodgepole pine (from −25.9 to −23.4‰), whereas soil compaction effects on foliar δ13C were observed only within the FF intact treatment. This result and the more negative foliar δ13C with increasing seedling growth most likely reflected limitation on CO2 diffusion due to water stress caused by those treatments. However, foliar δ13C of Douglas-fir (range −25.0 ∼ −24.5‰) were not affected by the treatments, indicating less susceptibility to water stress. Soil compaction reduced NH4+-N concentrations in the FF (from 48.5 to 28.0) and NO3−-N concentrations in the FF (from 13.8 to 6.4) and mineral soil (from 4.3 to 2.1 mg kg−1), and FF removal tended to decrease NH4+-N concentrations in the mineral soil. Foliar δ15N of both species were not affected by soil compaction but were increased by the FF removal and rehabilitation treatments, indicating that the latter two treatments dramatically altered soil N dynamics. FOR. SCI. 51(6):546–555.

Mismatch between Herbivore Behavior and Demographics Contributes to Scale-Dependence of Host Susceptibility in Two Pine Species - Tiina Ylioja; Daniel H. Slone; Matthew P. Ayres (Forest Science, 2005)
The impacts on forests of tree-killing bark beetles can depend on the species composition of potential host trees. Host susceptibility might be an intrinsic property of tree species, or it might depend on spatial patterning of alternative host species. We compared the susceptibility of loblolly pine (Pinus taeda) and Virginia pine (P. virginiana) to southern pine beetle (Dendroctonus frontalis) at two hierarchical levels of geographic scale: within beetle infestations in heterospecific stands (extent ranging from 0.28 to 0.65 ha), and across a forest landscape (extent 72,500 ha) that was dominated by monospecific stands. In the former, beetles preferentially attacked Virginia pine (tree mortality = 65–100% in Virginia pine versus 0–66% in loblolly pine), but in the latter, loblolly stands were more susceptible than Virginia stands. This hierarchical transition in host susceptibility was predicted from knowledge of (1) a behavioral preference of beetles for attacking loblolly versus Virginia pine, (2) a negative correlation between preference and performance, and (3) a mismatch in the domain of scale between demographics and host selection by individuals. There is value for forest management in understanding the processes that can produce hierarchical transitions in ecological patterns. FOR. SCI. 51(6):522–531.

Soil Compaction and Forest Floor Removal Affect Early Growth and Physiology of Lodgepole Pine and Douglas-Fir in British Columbia - Mohammed Kamaluddin; Scott X. Chang; Michael P. Curran; Janusz J. Zwiazek (Forest Science, 2005)
We investigated the effects of soil compaction and forest floor removal on growth and physiology of lodgepole pine (Pinus contorta ex Loud. var. latifolia Engelm.) and Douglas-fir (Pseudotsuga menziesii var. glauca [Baissn.] Franco) seedlings on a calcareous long-term soil productivity (LTSP) study site near Invermere, British Columbia. Treatments consisted of factorial combinations of soil compaction (noncompacted versus compacted) and forest floor removal (forest floor intact versus forest floor removed) as well as a remedial (rehabilitation) treatment of deep ripping following soil compaction. The experiment was not replicated at the treatment plot level, therefore no statistically based mean comparisons were made. After two growing seasons, we found that the two tree species responded differently to those treatments. Lodgepole pine height and diameter growth and unit needle-weight (dry mass per unit needle) averaged 25, 51, and 30% greater, respectively, in the rehabilitation than in the other treatments, whereas Douglas-fir responded to the rehabilitation treatment by increasing stem diameter growth by 27%, but not height growth (a change of 9%). Forest floor removal decreased height growth in lodgepole pine by 11%, but increased diameter growth in Douglas-fir by 15%. The decreases in growth for lodgepole pine in the forest floor removal treatments were accompanied by lower foliar N concentrations. Foliar N concentrations were positively correlated with rates of net photosynthesis (r = 0.69, P = 0.004) and height growth (r = 0.76, P = 0.004) in lodgepole pine, but not in Douglas-fir. Low N supply (as observed for lodgepole pine) and depletion of soil moisture as a result of forest floor removal likely played a role in shaping the growth and physiological responses of the trees in this study. FOR. SCI. 51(6):513–521.

Simulating Landscape-Level Effects of Constraints to Public Forest Regeneration Harvests due to Adjacent Residential Development in Northern Wisconsin - Brendan C. Ward; David J. Mladenoff; Robert M. Scheller (Forest Science, 2005)
Residential development in rural forests is currently one of the most prominent land use changes in the United States. Such development can have important effects on ecosystem processes and landscape patterns. It can also constrain forest management on public lands, influencing tree species composition and age structure at the landscape scale. We used the forest landscape simulation model LANDIS-II to analyze changes to the landscape patterns of tree species composition, age structure, windthrow disturbance, and aboveground live biomass across a range of constraints to public forest timber harvests on a northern Wisconsin landscape. Our results demonstrate that decreasing harvest area through the use of buffers reduces the dominance of early-successional species, increases the dominance of mid to later-successional species, and shifts the stand age distribution within the landscape toward older forests. These buffers increase the spatial heterogeneity of dominant species and age structure at the landscape scale, and lead to more windthrow disturbance. We believe that our study can inform policymakers, forest managers, and scientists about potential long-term landscape-level effects of interaction between residential development and forest management. FOR. SCI. 51(6):616–632.

Spatial Continuity of Tree Attributes in Bottomland Hardwood Forests in the Southeastern United States - Luben D. Dimov; Jim L. Chambers; Brian Roy Lockhart (Forest Science, 2005)
Sustainable forest management and conservation require understanding of underlying basic structural and competitive relationships. To gain insight into these relationships, we analyzed spatial continuity of tree basal area (BA) and crown projection area (CPA) on twelve 0.64-ha plots in four mixed bottomland hardwood stands in Louisiana, Arkansas, and Mississippi. Variogram range indicated that BA spatial continuity of trees with dbh >10.0 cm extended an average 4.5 m. This distance equaled the quadratic mean crown radius (QMCR) of the overstory trees. Overall, 95% of the variability in BA was accounted for by the spatially structured variance and could be modeled as spatial dependence. Removal of suppressed trees from the analyses reduced the variability in BA at small separation distances and increased the variogram range. The average spatial continuity of unsuppressed trees averaged 18.2 m and was 17.6, 18.5, and 18.5 m based on the BA variograms, CPA variograms, and cross-variograms, respectively. This distance corresponded to four times the QMCR of the overstory trees and extended far enough to encompass the first- and second-order neighbors. The results suggest an existence of complex competitive influences and confirm findings in nonwoody vegetation that competitive effects can propagate beyond the direct neighbors. FOR. SCI. 51(6):532–540.

Correction (Forest Science, 2005)

Airtanker Flight Distance between Fires: Random Fire Starts on Line Segments - Francis E. Greulich (Forest Science, 2005)
Under high initial attack fire loads, dispatchers sometimes redirect airtankers that are working on other fires. The inherent variability of flight distance between random fire locations is a potentially important aspect of any model that would reallocate the airtanker resource between fires. Requisite formulas are derived, and computational procedures are provided in this article for the stochastic description of airtanker flight distances between fire-start locations randomly located along straight-line segments. Numerical approximations and comparisons with prior work confirm the results of detailed examples that establish a blueprint for application and continued model development. FOR. SCI. 51(5):460–471.

Effects of Fertilization and Vegetation Control on Microbial Biomass Carbon and Dehydrogenase Activity in a Juvenile Loblolly Pine Plantation - Michael A. Blazier; Thomas C. Hennessey; Shiping Deng (Forest Science, 2005)
To characterize the influences of fertilization and understory vegetation suppression on microbial biomass and activity in a juvenile loblolly pine plantation, we measured microbial biomass C (Cmic) and dehydrogenase activity in soil monthly in response to (1) untreated control (CONT), (2) understory suppression with glyphosate (BC), (3) pine removal (NP), (4) pine removal with understory suppression (NPBC), (5) urea + diammonium phosphate with understory suppression (UDBC), and (5) slow-release urea with understory suppression (CUFBC). Cmic and dehydrogenase activity were significantly decreased relative to the CONT treatment by the NP, NPBC, UDBC, and CUFBC treatments. These reductions likely indicate a dependence of soil microbes on labile C sources derived from living vegetation. Fertilization + brush control decreased Cmic and dehydrogenase activity to a greater extent than brush control alone, suggesting that the availability of labile C sources was adversely affected by fertilization. Short-term reductions in Cmic were correlated with increases in soil NO3−. Results of this study demonstrate that, in this young, intensively managed pine plantation, labile C substrates from vegetation may be a predominant determinant of soil N availability through its influence on microbial biomass and activity. FOR. SCI. 51(5):449–459.

Analyzing the Spread of Beech Canker - Nicole H. Augustin; Edgar Kublin; Berthold Metzler; Elsa Meierjohann; Georg von Wühlisch (Forest Science, 2005)
We investigate the spread of Nectria canker of beech, which is a fungal chronic disease caused by Nectria ditissima Tul. et C. Tul. Data are available from a beech provenance trial. A possible influential factor on the proportion of infected trees per plot is the wind dispersal zone(s) (wdz), a categorical variable describing the distance and wind direction from diseased shelterwood, the source of infection. We investigate the effect of wdz and whether the disease incidence in the regeneration can be explained alone by the wdz using different approaches accounting for spatial correlation in the data. One method uses generalized estimating equations (GEE) where, through specification of a general variance–covariance matrix allowing for nonindependence, spatial correlation can be accounted for in the model. The second method uses generalized additive models (GAM) and the spatial autocorrelation is dealt with by modeling it as a spatial trend. The third method uses generalized linear mixed models (GLMM) with a random effect accounting for spatial correlation and heterogeneity. We show that, in the beech data, some spatial correlation is present that is over and above that accounted for by the wdz. Therefore, methods not accounting for this correlation are inappropriate. The GLMM is the most appropriate model because it manages to model the biological process best: It explains the variation in disease incidence by the wdz and by secondary infection. Hence it yields the most precise estimates. FOR. SCI. 51(5):438–448.

Confirmation of Oak Recruitment Failure in Indiana Old-Growth Forest: 75 Years of Data - Preston R. Aldrich; George R. Parker; Jeanne Romero-Severson; Charles H. Michler (Forest Science, 2005)
We report on a long-term study of changes in the diameter distribution of red and white oaks in old-growth forest of Indiana. We expand the scope of a prior 50-year demographic study of a 20.6-ha stand by (1) extending the census period, (2) comparing diameter distributions in the large stand with those of a smaller (2.3-ha) stand, and (3) examining small-diameter ingrowth of red oaks into both stands. Oaks displayed bell-shaped or even-aged diameter distributions in 1926, suggesting a history of disturbance from timber removal, grazing, and fire. These exogenous disturbances were suppressed starting in 1917 with acquisition of the property by Purdue University. Subsequent censuses indicated considerable ingrowth of nonoak stems into both stands. Oaks that were mid-sized in 1926 gradually moved through the size classes and were replaced by younger individuals in the small stand but not in the center of the large stand. The survey of red oak saplings confirmed this pattern, revealing numerous recruits in the small stand but virtually none in the large stand. These data support the view that oaks are failing to regenerate in part due to shade-intolerance and a waning disturbance regime in the large stand interior. FOR. SCI. 51(5):406–416.

Variation in Wood Density and Shrinkage and Their Relationship to Growth of Selected Young Poplar Hybrid Crosses - Alfas Pliura; Qibin Yu; S. Y. Zhang; John MacKay; Pierre Périnet; Jean Bousquet (Forest Science, 2005)
Wood density, various shrinkages and several growth traits were measured in two 10-year-old clonal trials at sites of contrasting growth potential. The material studied consisted of 12 clones of three poplar hybrid crosses, Populus deltoides × P. nigra, P. trichocarpa × P. deltoides, and P. maximowiczii × P. balsamifera, as well as P. deltoides. Wood density and longitudinal and radial wood shrinkages were significantly lower at the St-Ours than at the Windsor site, by 6.7, 46.7, and 14.9%, respectively, while growth rate was increased. The differences among hybrid crosses were significant for all growth traits and wood properties except for radial and tangential shrinkages of juvenile wood. P. deltoides had the highest wood density of 363.2 kg/m3, whereas P. maximowiczii × P. balsamifera wood had the lowest density of 299.8 kg/m3. The differences among hybrid crosses were significant for growth traits, primarily due to the fast growth of P. trichocarpa × P. deltoides and slow growth of P. deltoides. Among the wood properties measured, only tangential wood shrinkage exhibited clear radial intertree changes with cambial age. The tangential wood shrinkage increased from pith to mid-diameter and then started to decrease outward, with each hybrid showing a different pattern of variation. Phenotypic clonal mean correlations among growth traits and wood density were weakly negative. Correlations among growth traits and radial wood shrinkage ranged from weakly to strongly negative. Longitudinal shrinkage displayed strong negative correlations with radial and tangential shrinkages. Negative correlations found between wood density and longitudinal shrinkage and positive correlations between density and both radial and tangential shrinkages suggest that selection for high wood density may lead to increased transverse wood shrinkage but decreased longitudinal shrinkage. FOR. SCI. 51(5):472–482.

Mixed Conifer Forest Duff Consumption during Prescribed Fires: Tree Crown Impacts - Marco G. Hille; Scott L. Stephens (Forest Science, 2005)
Fire suppression has produced large forest floor fuel loads in many coniferous forests in western North America. This study describes spatial patterns of duff consumption in a mixed-conifer forest in the north-central Sierra Nevada, California. Overstory crown coverage was correlated to spatial patterns of duff depth after prescribed fire. On one site that was burned under dry conditions, almost all duff was consumed, with some remaining in overstory gaps. On a second site that was burned under moist conditions a few days after the first annual precipitation, strong spatial patterns of duff consumption were recorded with increasing distance from the base of the nearest overstory tree, the probability of duff remaining after prescribed fire increased significantly. There is strong evidence that spatial variation of precipitation throughfall resulted in higher duff moisture in gaps, whereas duff beneath crown cover was drier, and therefore, totally consumed. This study demonstrates that including a spatial component in a process-based duff consumption model would improve the accuracy of fire-effect predictions. FOR. SCI. 51(5):417–424.

BOOK REVIEW: Modern Biogeochemistry - Scott Chang (Forest Science, 2005)
Professor Bashkin's recent book “Modern Biogeochemistry” provides an in-depth analysis of the many aspects of biogeochemistry of some key chemical elements in a wide variety of ecosystems. The book essentially evolved from the lectures professor Bashkin gave at the Universities of Cornell, Moscow, Pushchino, Seoul, and Bangkok.

A New Simulator for the Spread of Forest Root Diseases by Individual Root Contacts - F. G. Peet; R. S. Hunt (Forest Science, 2005)
A new simulator for the spread of forest root diseases, and the testing of it, is presented. It differs from earlier models in that it represents a first step to incorporate the basic processes of spread by individual root contact. It therefore has a generality that allows its use in different host–pathogen and geographic situations. It stochastically grows individual roots longitudinally outward from the stem. They are tapered, turn, and contact other roots as they grow. The simulator transfers fungus stochastically at points of contact between healthy roots and infected stump or tree roots and moves the fungus along infected tree roots stochastically. The fungus can girdle the rootcollar, move out into other roots, and eventually kill the tree. Growth of roots and fungus movement along infected roots is on an annual basis for up to 200 years. Root growth, fungus growth along roots, disease spread, and stand openings are displayed dynamically in color on the computer screen as the simulation proceeds. Estimates for numbers of infected trees and mortality are provided in tabular and graphical form. Results from the simulator were close to the field data it was tested against. FOR. SCI. 51(5):425–437.

Forecasting Germany's Printing and Writing Paper Imports - Lauri Hetemäki; Jarmo Mikkola (Forest Science, 2005)
Short-term forecasting of forest products demand is one of the key inputs for successful market planning in the forest sector. Currently, this field is dominated by consultants' and industry analysts' forecasts, which are often based on methods and procedures that are not well documented, or are ad hoc. This article seeks to contribute to the scarce literature on this topic by presenting results for short-term forecasts for the import demand for coated printing and writing paper in Germany. A number of univariate time series models, single equation econometric models, and multivariate systems models are estimated using quarterly data from 1991:Q1–2001:Q2, and observations from 2001:Q3–2002:Q4 are used for the out-of-sample forecast performance evaluation. Forecasts are also computed using various weighted combinations of the individual forecasting models. The results indicate that forecast accuracy increases when one moves from univariate time series models to econometric models. The best single forecasting model in terms of the root-mean-squared error criterion is a VARX model in differences. However, by optimally combining individual model forecasts, one is able to produce even more accurate forecasts. FOR. SCI. 51(5):483–497.

Changes in Snag Populations in Northern Arizona Mixed-Conifer and Ponderosa Pine Forests, 1997–2002 - Joseph L. Ganey; Scott C. Vojta (Forest Science, 2005)
Snags (standing dead trees) are important components of forests that contribute to ecological processes and provide habitat for many life forms. We monitored dynamics of snag populations on 1-ha plots in southwestern mixed-conifer (n = 53 plots) and ponderosa pine (Pinus ponderosa, n = 60 plots) forests in north-central Arizona from 1997 to 2002. Of 2,240 snags marked in 1997, at least 76% remained standing in 2002, 17% had fallen and were relocated as logs, 0.5% were cut down, and the remainder (6%) were unaccounted for. Snag density increased significantly in mixed-conifer forest but not in ponderosa pine forest. Snag density increased mainly in the smaller size classes in both forest types. Density of large snags (≥46 cm in diameter and 9 m in height) increased slightly but nonsignificantly from 1997 levels in both forest types, and fell below current targets for retention. Species composition of snags differed between 1997 and 2002 in ponderosa pine forest, but not in mixed-conifer forest, and decay-class distributions differed among years in both forest types. A classification-tree analysis indicated that a ratio of height to diameter, species, and diameter were key variables in predicting whether a snag survived from 1997 to 2002. These results provide empirical data on snag populations and dynamics in this area and establish a basis for longer-term monitoring of snag populations and dynamics. FOR. SCI. 51(5):396–405.

An Alternative Incentive Structure for Wildfire Management on National Forest Land - Geoffrey H. Donovan; Thomas C. Brown (Forest Science, 2005)
Wildfire suppression expenditures on national forest land have increased over the last 35 years, exceeding US$1 billion in 2000 and 2002. These increases in expenditure have been attributed, in part, to a century of aggressive wildfire suppression, resulting in a buildup of fuel on the nation's forests. The efficiency of the current incentive structure faced by Forest Service fire managers is analyzed. An alternative incentive structure is presented that encourages fire managers, as they work to limit wildfire damages, to contain costs and consider the beneficial effects of wildfire. FOR. SCI. 51(5):387–395.

Acacia mangium , a Nurse Tree Candidate for Reforestation on Degraded Sandy Soils in the Malay Peninsula - M. Norisada; G. Hitsuma; K. Kuroda; T. Yamanoshita; M. Masumori; T. Tange; H. Yagi; T. Nuyim; S. Sasaki; K. Kojima (Forest Science, 2005)
We investigated the suitability of Acacia mangium Willd., a fast-growing tropical leguminous tree, as a nurse tree for reforestation with indigenous species on severely degraded sandy soils in southern Thailand. Planting A. mangium yielded a survival rate of 91% and satisfactory growth (7.7 m height, 56 mm dbh, 59 Mg dry weight ha−1 aboveground biomass) 45 months after planting, indicating the species' suitability for reforestation. Three dipterocarp species (Dipterocarpus alatus Roxb. ex G. Don, Hopea odorata Roxb., and Shorea roxburghii G. Don.) planted simultaneously with A. mangium showed better growth than when planted alone. Seedlings of all three dipterocarp species that survived transplanting showed better survival when planted with A. mangium. The findings suggest A. mangium is an effective nurse tree for dipterocarp seedlings. The carbon and nitrogen contents of surface soil did not increase in the A. mangium stands. Microclimate measurements showed moderated air temperature, relative humidity, and soil temperature in the mixed planting. The moderated microclimate under the A. mangium canopy is thought to be responsible for the improved growth of the dipterocarp seedlings. If dipterocarp seedlings are planted after A. mangium grows enough to provide shade, initial survival rates should improve. FOR. SCI. 51(5):498–510.

Multilevel Nonlinear Mixed-Effects Models for the Modeling of Earlywood and Latewood Microfibril Angle - Lewis Jordan; Richard F. Daniels; Alexander Clark; Rechun He (Forest Science, 2005)
Earlywood and latewood microfibril angle (MFA) was determined at 1-millimeter intervals from disks at 1.4 meters, then at 3-meter intervals to a height of 13.7 meters, from 18 loblolly pine (Pinus taeda L.) trees grown in southeastern Texas. A modified three-parameter logistic function with mixed effects is used for modeling earlywood and latewood MFA. By making the parameters of the logistic function linear functions of height, a three-dimensional model was developed that describes the changes of earlywood and latewood MFA within the tree. A first-order autoregressive correlation structure and a variance model corresponding to a variance covariate given by the fitted values for each wood type, but in which the proportionality constant differs according to the level of wood type, was identified as the within-group correlation and variance structures. Cross-validation was used to determine model accuracy and precision. The methods of model development including determination of the height structure, which parameters should be considered random or fixed, determination of an appropriate variance-covariance structure, and prediction are addressed. Model performance was evaluated utilizing informative statistics including likelihood ratio tests (LRTs), Akaike information criterion (AIC), and Bayesian information criterion (BIC). FOR. SCI. 51(4):357–371.

Localizing a Predicted Diameter Distribution Using Sample Information - Lauri Mehtätalo (Forest Science, 2005)
This study presents a new method for predicting the diameter distribution of a stand, utilizing the percentile-based diameter distribution. The expected diameter percentiles are first predicted using stand measurements. Subsequently, the distribution is calibrated (localized) for the stand using sample order statistics, which consist of one or more diameters of sample trees and their ranks on the sample plot(s). These measurements can be quickly carried out in the field, because the rank can be assessed visually. The sample order statistics can be interpreted as measured sample percentiles. The expectations, variances, and covariances of the measured sample order statistics are derived using the theory of order statistics. Regression models are used to predict the conditional expectations of predefined percentiles, which are then combined with the measured percentiles using the best linear unbiased predictor. The method was tested in a real data set using simulated sample plots. The test showed that, even with a small number of sample measurements, the relative root mean square error and bias of volume per hectare could be decreased remarkably. Furthermore, increasing the number of measurements steadily improved the prediction. The proposed method seems to be a promising tool in the prediction of diameter distributions of various forms, including those found in complex stands. FOR. SCI. 51(4):292–303.

Comparing and Combining Stem Analysis and Permanent Sample Plot Data in Site Index Models - Oscar García (Forest Science, 2005)
Most site index models are built either from repeated measurements on permanent sample plots or by using data obtained by stem analysis. Sometimes both types of data are available. It is then of interest to test them for consistent height-age trends, and to estimate model parameters using all the data. Efficient procedures should take into account the difference in error patterns between the two data sources. A stochastic differential equation model is proposed in which trend and error parameters can take either different or common values for various data groups. All parameters are simultaneously estimated by maximum-likelihood, and computed likelihoods and likelihood-ratio tests can be used for comparing model variants and for hypothesis testing. The methods are applied to Pinus pinaster plantations in northern Spain. FOR. SCI. 51(4):277–283.

Aquatic Invertebrate Responses to Timber Harvest in a Bottomland Hardwood Wetland of South Carolina - Darold P. Batzer; Bagie M. George; Amy Braccia (Forest Science, 2005)
We used aquatic invertebrates to assess environmental impacts of timber harvest on a bottomland hardwood wetland in the Coosawhatchie River floodplain, Jasper County, SC. Two years (1998, 1999) of preharvest baseline data were collected during winter floods in three 11–13-ha tracts of wetland forest. The following autumn of 1999 one tract was completely clearcut. In a second tract the majority of the area was also clearcut, but three 0.2–0.6-ha islands of intact forest were retained (i.e., patch-retention treatment). The third tract remained intact and served as the control. We continued to sample invertebrates in the three tracts for another 2 years (2000, 2001) after harvests. Invertebrate communities in the clearcut tract differed significantly from previous baseline conditions in that habitat and also from the nearby control tract. The patch-retention tract induced a lesser response than the clearcut, suggesting that retention islands helped mitigate impacts. Timber harvest caused a decline in some invertebrate populations (Asellidae, Crangonyctidae, Planorbidae), but an increase in others (Culicidae). Overall invertebrate abundance and family richness was not affected by harvest, only community composition. Invertebrate change probably reflected a conversion of a fauna typical of forested wetland to one typical of herbaceous wetland. FOR. SCI. 51(4):284–291.

Molecular Genetics and Breeding of Forest Trees - Gary F. Peter (Forest Science, 2005)

A Variance and Covariance Equation for Area Estimates with a Geographic Information System - P. A. J. van Oort; A. Stein; A. K. Bregt; S. de Bruin; J. Kuipers (Forest Science, 2005)
Geographic Information Systems automatically calculate the area of a polygon from the coordinate values of the vertices that describe its boundary. Uncertainty in these coordinate values results in uncertainty in area estimates. Earlier articles showed how area uncertainty of individual polygons could be calculated. In this article we propose a covariance equation to quantify the impact of uncertainty in the position of a vertex on uncertainty in the area of all polygons sharing this vertex. The approach is based on the assumption of absence of spatial correlation in positional errors, but includes variation in the positional accuracy. The equations were implemented and applied to a case study area, described by a set of 97 adjacent polygons with different per unit area utility values (€/ha). We were then able to calculate how uncertainty in the coordinate values propagated into uncertainty in the utility value of the complete set of polygons. FOR. SCI. 51(4):347–356.

Forest and Pasture Carbon Pools and Soil Respiration in the Southern Appalachian Mountains - Paul V. Bolstad; James M. Vose (Forest Science, 2005)
Our ability to estimate the changes in carbon (C) pools and fluxes due to forest conversion is hampered by a lack of comparative studies. We measured above- and belowground C pools and soil respiration flux at four forested and four pasture sites in the southern Appalachian Mountains. Above- and belowground C pools were significantly larger (P < 0.01, t-test) at forested sites relative to pasture sites. The largest differences were in aboveground live biomass, which averaged 152 Mg ha−1 C at the forested sites and 1.9 Mg ha−1 at the pasture sites. Coarse root and stump C and surface detritus were also substantially different, averaging 41.3 and 32.6 Mg ha−1 C, respectively, at the forested sites, and less than 1 Mg ha−1 at the pasture sites. Fine root C was higher and mineral soil C lower at pasture sites relative to comparable forested sites, but neither difference was statistically significant. Soil respiration at a given temperature was generally lower at pasture sites relative to forest sites. However, soil temperatures at pastures were consistently higher than at forest sites. Estimated annual soil respiration flux averaged 10.9 Mg C ha−1 at the pasture sites and 12.6 Mg C ha−1 at the forested sites. FOR. SCI. 51(4):372–383.

Spatial Assessment of Model Errors from Four Regression Techniques - Lianjun Zhang; Jeffrey H. Gove (Forest Science, 2005)
Forest modelers have attempted to account for the spatial autocorrelations among trees in growth and yield models by applying alternative regression techniques such as linear mixed models (LMM), generalized additive models (GAM), and geographically weighted regression (GWR). However, the model errors are commonly assessed using average errors across the entire study area and across tree size classes. Little attention has been paid to the spatial heterogeneity of model performance. In this study, we used local Moran coefficients to investigate the spatial distributions of the model errors from the four regression models. The results indicated that GAM improved model-fitting to the data and provided better predictions for the response variable. However, it is nonspatial in nature and, consequently, generated spatial distributions for the model errors similar to the ones from ordinary least-squares (OLS). Furthermore, OLS and GAM yielded more clusters of similar (either positive or negative) model errors, indicating that trees in some subareas were either all underestimated or all overestimated for the response variable. In contrast, LMM was able to model the spatial covariance structures in the data and obtain more accurate predictions by accounting for the effects of spatial autocorrelations through the empirical best linear unbiased predictors. GWR is a varying-coefficient modeling technique. It estimated the model coefficients locally at each tree in the example plot and resulted in more accurate predictions for the response variable. Moreover, the spatial distributions of the model errors from LMM and GWR were more desirable, with fewer clusters of dissimilar model errors than the ones derived from OLS and GAM. FOR. SCI. 51(4):334–346.

Assessment of Sustainability in Intensively Managed Forested Landscapes: A Case Study in Eastern Texas - João C. Azevedo; X. Ben Wu; Michael G. Messina; Richard F. Fisher (Forest Science, 2005)
We developed a methodology to analyze the effects of management practices on landscape structure and function to be used in the assessment of sustainability in intensively managed forest landscapes. It is based on modeling and simulation of landscape and stand structure as well as biological and physical processes. The methodology includes a landscape structure model and several forest stand-level models to simulate the dynamics of landscapes and stands as a function of management rules. It also includes habitat models to evaluate landscape quality and spatial characteristics of vertebrate habitat, and a hydrologic model to simulate water and sediment yield at the subarea and watershed levels. The application of this methodology to the Sustainable Forestry Initiative (SFI) program in eastern Texas indicated that this is an effective way to evaluate effects of sustainable forestry programs on landscape structure and processes. During simulation years, the habitat of pine warbler, the species used as an example to illustrate the methodology, became apparently fragmented under the SFI scenario. This fragmentation was caused mainly by narrow, forested streamside management zones dissecting pine stands and should have little negative influence on the pine warbler habitat. Sediment yield at the landscape level decreased by the implementation of SFI measures, particularly by the reduction of channel degradation. FOR. SCI. 51(4):321–333.

A Re-Evaluation of Reineke's Rule and Stand Density Index - Hans Pretzsch; Peter Biber (Forest Science, 2005)
The self-thinning rule established by Reineke in 1933, N α d−1.605 (N, d = number of stems and quadratic mean diameter, respectively) assumes the same allometric relationship between size and density for a wide spectrum of species under self-thinning conditions. We re-evaluate this rule based on 28 fully stocked pure stands of common beech (Fagus sylvatica L.), Norway spruce (Picea abies [L.] Karst.), Scots pine (Pinus sylvestris L.), and common oak (Quercus petraea [Mattuschka] Liebl.) in Germany that date back to the year 1870. OLS regression of the model ln(N) = a + b · ln(d) results in b values of −1.789 for common beech, −1.664 for Norway spruce, −1.593 for Scots pine, and −1.424 for common oak. The allometric coefficient for common beech differs significantly from the other species. There is also a significant difference between the b values of Norway spruce and common oak. Except for Scots pine, the above allometric coefficients deviate significantly (common beech) and close-to-significantly (Norway spruce, common oak) from the coefficient −1.605 postulated by Reineke in 1933. To cover the species–specific oscillation of mortality rates, we additionally calculate the self-thinning coefficient for each survey period. Ecological implications of the species-specific scaling exponents are stressed and consequences regarding tools for regulating stand density are discussed. FOR. SCI. 51(4):304–320.

Biophysical Controls on Soil Respiration in the Dominant Patch Types of an Old-Growth, Mixed-Conifer Forest - Siyan Ma; Jiquan Chen; John R. Butnor; Malcolm North; Eugénie S. Euskirchen; Brian Oakley (Forest Science, 2005)
Little is known about biophysical controls on soil respiration in California's Sierra Nevada old-growth, mixed-conifer forests. Using portable and automated soil respiration sampling units, we measured soil respiration rate (SRR) in three dominant patch types: closed canopy (CC), ceanothus-dominated patches (CECO), and open canopy (OC). SRR varied significantly among the patch types, ranging from 2.0 to 4.5 µmol m−2 s−1 and from 0.9 to 2.9 µmol m−2 s−1 during the 1999 and 2000 measuring periods, respectively, with the maximum in CECO and the minimum in OC. Multiple peaks of seasonal SRR were functions of soil temperature and moisture dynamics. The relationship between SRR and soil temperature switched from a positive to a negative correlation when soil moisture dropped from saturation to drought. Time lag, as a function of soil moisture, was included in an exponential model to assess the effects of soil moisture on SRR in this seasonal water-stressed ecosystem. The total soil C flux summed by an area-weighted average across all three patch types was 660 ± 163 g C m−2 from May to Oct. 2000. These results may be applicable to other water-stressed forests in the Mediterranean climate zone, and have implications for the conservation of soil carbon. FOR. SCI. 51(3):221–232.

Soil Arthropod Responses to Different Patch Types in a Mixed-Conifer Forest of the Sierra Nevada - James L. Marra; Robert L. Edmonds (Forest Science, 2005)
The Teakettle Ecosystem Experiment in the southern Sierra Nevada is using thinning and prescribed fire to recreate historical stand conditions. As part of Teakettle we assessed pretreatment diversity and density of the soil arthropod community in 1998 and 2000. We determined the density and diversity of soil microarthropods among treatment plots, the influence of patch type (closed canopy, canopy gaps, Ceanothus sp., and coarse woody debris [CWD]), and established baseline pretreatment data. Mites were the dominant microinvertebrates (78%). Canopy gaps had the lowest mite density and diversity, and were more sensitive to year-to-year changes in climate (1998 was an extremely wet year for the region). Soil organic matter as represented by bulk density appeared to be most closely associated with changes in species composition among different patch types. There was substantial overlap, however, in community composition among the different patch types as represented by nonmetric multidimensional scaling (NMS) ordination. No significant differences were observed for mite species richness and density among plots assigned to future treatments. The gap data suggest that in the characteristically hot, dry summers of the southern Sierra Nevada the rate of recovery of vegetation following thinning and fire treatments may have a significant influence on the recovery rate of microarthropods, not only by providing sources of energy inputs in the form of dead organic matter, but also by moderating the microclimate of the forest floor. FOR. SCI. 51(3):255–265.

Canopy Arthropod Assemblages in Four Overstory and Three Understory Plant Species in a Mixed-Conifer Old-Growth Forest in California - Timothy D. Schowalter; Yanli Zhang (Forest Science, 2005)
We compared canopy arthropod assemblages among overstory conifer and understory angiosperm species at Teakettle Experimental Forest in the Sierra Nevada in California during 1998–2000. Arthropods were sampled from upper, middle, and lower crown levels of one overstory tree of each of the four dominant conifer species (Jeffrey pine, sugar pine, white fir, and incense cedar), and from three understory plants of each of the major understory species (California black oak, manzanita, and white-thorn ceanothus) in each of five replicate plots during June and Aug. in each of the 3 years to represent seasonal and annual variation in abundances. Many taxa differed significantly in abundance among plant species, with one to five taxa being significant indicators for each plant species. Five to eight taxa on each plant species showed significant differences in abundance among years. Aphids and scale insects, predaceous mirids, and some detritivores showed peak abundances in 1999, a particularly dry year, whereas most other taxa showed lowest abundances during 1999 or declining abundances during this period, suggesting association with wetter conditions. Nonmetric multidimensional scaling (NMS), supported by multi-response permutation procedure (MRPP), showed that arthropod assemblages differed significantly among the seven plant species, especially between overstory conifers and understory angiosperms, and among the 3 years. These data indicate that the diversity and structure of arthropod communities depend on vegetation structure and/or condition, perhaps as modified by annual variation in weather conditions. FOR. SCI. 51(3):233–242.

Hypogeous Ectomycorrhizal Fungal Species on Roots and in Small Mammal Diet in a Mixed-Conifer Forest - Antonio D. Izzo; Marc Meyer; James M. Trappe; Malcolm North; Thomas D. Bruns (Forest Science, 2005)
The purpose of this study was to estimate the portion of an ectomycorrhizal (ECM) fungi root community with a hypogeous fruiting habit. We used molecular methods (DNA sequence analysis of the internally transcribed spacer [ITS] region of rDNA) to compare three viewpoints: ECM fungi on the roots in a southern Sierra Nevada Abies-dominated old-growth forest, fungi in scat samples collected from small mammals in the same forest, and hypogeous sporocarps found throughout the Sierra Nevada. We found that hypogeous taxa accounted for a minimum of 21% of the species and 25–40% of the dry root biomass of all samples. This estimate is two to three times greater than estimates from previous studies. This difference may be due to methodological advantages of this study, but may also be related to conditions in dry forests typical of western North America where prolonged drought may favor this form of fruiting. Although molecular analysis of scat samples did not add to our view of the ECM roots, we readily isolated sequences from Rhizopogon species. From these results we inferred that two species, R. occidentalis and R. olivaceotinctus, are represented primarily in the spore bank and may be dependent on substantial disturbance to become abundant on roots. FOR. SCI. 51(3):243–254.

Effects of Vegetation Patches on Soil Nutrient Pools and Fluxes within a Mixed-Conifer Forest - Heather E. Erickson; Patricia Soto; Dale W. Johnson; Brent Roath; Carolyn Hunsaker (Forest Science, 2005)
At a spatially heterogeneous mixed-conifer forest in the central California Sierras, we quantified total carbon (C) and nitrogen (N), inorganic N, and net N mineralization in organic (O) and surface (0–15 cm) mineral soils, and in situ fluxes of inorganic N and ortho-phosphate using resin lysimeters under three patch types: closed canopy conifer, sparsely vegetated open canopy, and Ceanothuscordulatus thickets. In O horizons, total N and C pools ranked: closed canopy > Ceanothus > open canopy. In mineral soils, total N pools under Ceanothus exceeded those under closed canopy patches by about 30%. For 2 years, nitrate concentrations and rates of net N mineralization in O horizons were 4× greater under Ceanothus than under the other patch types. Similarly, ammonium concentrations and net N mineralization in mineral horizons were more than 80 and 200% greater, respectively, under Ceanothus than under the other patch types. In situ fluxes of nitrate were 4× greater beneath Ceanothus for 1 year, and no differences were found among the patch types for another year. Despite the interannual variability, our data suggest that Ceanothus contributes to a greater proportion of total N mineralized than based on cover alone, and may be important for forest nutrition under current conditions and after forest burning. FOR. SCI. 51(3):211–220.

Influence of Fire and El Niño on Tree Recruitment Varies by Species in Sierran Mixed Conifer - Malcolm North; Matthew Hurteau; Robert Fiegener; Michael Barbour (Forest Science, 2005)
The influence of fire and climate events on age structure of different species was examined in old-growth mixed conifer in the southern Sierra Nevada. Within a 48-ha stem-mapped sample area, after a mechanical thinning, all stumps were examined for fire scars and 526 stumps were cut to ground level and aged. Before 1865, which was the last widespread fire event, the mean interval between scars for an individual tree was 17.3 years and the mean fire return interval for the period with the greatest number of recording trees was 11.4 years. A significantly greater than expected number of fires occurred in dry La Niña years, but these fires were not significantly larger in size than fires in other years. The response of mixed-conifer recruitment to climate and fire events varied by species. Before 1865, Jeffrey pine and sugar pine recruitment were correlated with wet El Niño years, but only sugar pine establishment was associated with fire. Red fir recruitment did not follow fire events but was associated with El Niño years before and after 1865. Most white fir and incense cedar (84%), including many large-diameter trees (>76 cm dbh), recruited after the last widespread fire in 1865. Although tree distribution is clustered in the southern Sierra Nevada, mixed-conifer groups are not age cohorts because species have different recruitment patterns relative to climate and fire events. In mixed conifer, top-down effects of fire and weather on recruitment are mediated by different species responses to these effects and within-stand differences in where species are located. FOR. SCI. 51(3):187–197.

Introduction to the Special Issue on Sierran Mixed-Conifer Research - Malcolm North; Jiquan Chen (Forest Science, 2005)

Stand Conditions Associated with Tree Regeneration in Sierran Mixed-Conifer Forests - Andrew N. Gray; Harold S. J. Zald; Ruth A. Kern; Malcolm North (Forest Science, 2005)
Fire suppression has significantly increased canopy cover, litter depth, and stem density in many western forests, altering microsite conditions that affect tree seedling establishment. We conducted studies in a mixed-conifer forest in the Sierra Nevada, California, to determine relationships between established understory trees and microsite quality, and to examine the effect of fire intensity and shrub cover on seedling establishment. Most of the conifer species were found on microsites with relatively high soil moisture and relatively low direct solar radiation. All species had greater frequency under shadier conditions except for Jeffrey pine, which was found on drier, more open microsites. Although seedlings were more abundant on mineral soil than expected, intact litter and forest floor was not a barrier to establishment. Mortality of planted seedlings was high, particularly in exposed areas. Although shrub cover may initially aid survival, few conifer saplings were present in shrub-dominated patches, possibly because shrubs can be aggressive competitors for soil moisture. The lack of regeneration, logs, or snags in many openings suggest that large gaps are hostile environments for tree seedlings. Results suggest that reductions in shrub cover may benefit tree establishment, but increasing understory light and decreasing surface soil moisture through canopy cover reductions may not. FOR. SCI. 51(3):198–210.

Patterns of Mortality in an Old-Growth Mixed-Conifer Forest of the Southern Sierra Nevada, California - Thomas F. Smith; David M. Rizzo; Malcolm North (Forest Science, 2005)
Mortality patterns in an old-growth, mixed-conifer forest, in the absence of wildfire, were investigated at the Teakettle Experimental Forest from 2000 to 2002. We tested the hypothesis that after a century of fire suppression, pathogen- and insect-associated mortality (between episodic droughts) would be significantly greater on ingrowth trees (i.e., smaller-diameter, shade-tolerant species in high-density clusters). Using a survey of over 30,000 mapped trees, overall mortality, as measured by standing dead trees, was 8.7% of all stems ≥5 cm dbh. Mortality levels were proportional to the population size of the five dominant conifer species, white fir (Abies concolor), red fir (A. magnifica), incense cedar (Calocedrus decurrens), Jeffrey pine (Pinus jeffreyi), and sugar pine (Pinus lambertiana). There was also no significant difference in mortality between shade-tolerant and shade-intolerant species. All dead trees were clustered within plots. Mortality was significantly higher than expected for large-diameter trees (>100 cm dbh) with all conifer species combined and for each individual species, except Jeffrey pine. Small-diameter dead trees were grouped in high-density clusters. Mortality was less than expected among small-diameter trees (5–20 cm dbh) for all species combined, red and white fir, and sugar pine. Mortality for all conifers was higher than expected in areas of high stand density and lower in areas of low stand density. Mortality of small-diameter trees was clustered and particularly high in areas of high stand density. Our data suggest pathogen- and insect-associated mortality is significantly greater in areas of high stand density but it is not higher for shade-tolerant species. Furthermore, mortality is higher than expected for large-diameter trees, suggesting an acceleration of old-tree mortality under current fire suppression conditions. FOR. SCI. 51(3):266–275.

Motivations and Behaviors of New Forest Owners in Virginia - Angelina Kendra; R. Bruce Hull (Forest Science, 2005)
Forestry must find ways to remain relevant to its changing constituency and client base. Market segmentation techniques can help. This study assessed the motivations and forest practices of 661 people who recently purchased forested lands ranging in size between 0.8 and 20 ha in rapidly growing counties in Virginia. Cluster analysis techniques were used to identify six market segments: absentee investors (4%), professionals (13%), preservationists (16%), young families (19%), forest planners (21%), and farmers (21%). (The remaining 6% demonstrated no variance in their responses and were not clustered.) The results suggest that lifestyle and amenity concerns are much more important motivations for landownership than are timber production and economic concerns. We discuss communication strategies, management services, and landowner assistance programs that might appeal to people in each of the six market segments. FOR. SCI. 51(2):142–154.

Juvenile Genetic Parameters and Genotypic Stability of Pinus pinaster Ait. Open-Pollinated Families under Different Water and Nutrient Regimes - Rafael Zas; Josefa Fernández-López (Forest Science, 2005)
The purpose of this study was to estimate the impact of genotype × nutrient and genotype × water availability interactions in the maritime pine (Pinus pinaster Ait.) breeding program in Galicia (northwestern Spain). Twenty-nine open-pollinated families, randomly selected in a seed orchard, were cultivated for 23 weeks in a greenhouse in a split-plot design under controlled conditions. Two water regimes (high and low water supply) combined with two nutrient regimes (high and low nutrient supply) were applied by subirrigation. Both the irrigation and the fertilization treatments had a strong effect in all the assessed traits. Heritabilities for growth and biomass traits were moderate to high (0.2–0.5) in individual treatments, especially in those treatments that led to intermediate growth. However, when analyzing all treatments together, the impact of the family × treatment interactions led to an important reduction (0.1–0.2) of the heritability estimates. The results indicated that the genotype × water and genotype × nutrient interactions may be important and could not be ignored in the Galician maritime pine breeding program. However, the study of the family ecovalence values indicated that interactions are mainly due to some interactive families (7 to 31% of families). Culling several of the female parents with high ecovalence values would result in a stable breeding population and would be enough to overcome the interaction handicap in the breeding program. FOR. SCI. 51(2):165–174.

Comparison of Nearest Neighbor Methods for Estimating Basal Area and Stems per Hectare Using Aerial Auxiliary Variables - Valerie LeMay; Hailemariam Temesgen (Forest Science, 2005)
Simulations were used to compare variable-space nearest neighbor methods for imputing stems per ha and basal area per ha (ground measured) for complex stands (many species and sizes) of southeastern British Columbia, Canada. Species composition and other characteristics obtained for every stand by interpreting aerial photography were used as auxiliary variables. The simulations included three distance metrics (squared Euclidean distance, most similar neighbor, and absolute distance), three intensities of stands with full information (20%, 50%, and 80%), two sets of aerial variables (mixed versus moderately high correlations with ground variables), and three averaging methods (nearest neighbor, average of three nearest neighbors, and distance weighted average of three nearest neighbors weighted). Increasing the number of stands with full information to 50% from 20% resulted in increased accuracy, with no noticeable improvement with a further increase to 80%. Of the three distance metrics, the most similar neighbor measure gave good results in imputing stems per ha and basal area per ha, particularly when there was a mixture of correlations, high and moderate, between the auxiliary (aerial) variables, and the ground variables. No large gain was noted in using the average of three neighbors rather than a single neighbor. FOR. SCI. 51(2):109–119.

An Evaluation of Spatial Dependency in Juvenile Loblolly Pine Stands Using Stem Diameter - Bronson P. Bullock; Harold E. Burkhart (Forest Science, 2005)
A simultaneous autoregressive model (SAR) was used to evaluate the amount of spatial influence juvenile loblolly pine (Pinus taeda L.) stems in a plantation have on one another. The presence of spatial autocorrelation between stems in a stand indicates that the characteristics of one stem are related to the characteristics of neighboring stems. The stands evaluated in this study had planting densities that varied from 747 to 6,727 trees per hectare. The SAR model contains a spatial dependency parameter that captures the inter-tree influences. Analysis on detrended diameter data showed that across ages 2 to 5 for groundline diameter measurements and ages 5 to 11 for breast height diameter measurements, the simultaneous autoregressive model indicated significant spatial dependency parameters in 23.2% of the plots (alpha-level = 0.10). A generally increasing trend in the occurrence of significant spatial influence from 18.2% to 28.4% was noted with an increase in planting density from 747 to 3,364 trees per hectare, beyond which the trend decreased. Estimation of the spatial dependency parameter will aid in describing juvenile competition processes and developing a more precise representation of juvenile forest stands. FOR. SCI. 51(2):102–108.

Describing Leaf Area Distribution in Loblolly Pine Trees with Johnson's SB Function - Mauricio Jerez; Thomas J. Dean; Quang V. Cao; Scott D. Roberts (Forest Science, 2005)
The objective of this study is to evaluate the fit of Johnson's SB distribution function to vertical foliage distributions of variously aged and treated loblolly pine trees when the function is fit with two percentiles of the observed distributions. Foliage distributions are linked to various stand properties, and straightforward means of quantifying foliage distribution may lead to a convenient method of characterizing forest stands using remote sensing technology such as LiDAR. Regression analyses indicate that the 15th and 50th percentiles of the distributions were best correlated with variables of crown structure and tree age. Skewness and kurtosis of the distributions calculated with the function's parameters also varied with crown structure and age. Cumulative fractions of leaf area calculated with fitted SB functions matched measured values well; cumulative values of absolute leaf area showed less correspondence with measured values, but residuals of both centered around zero. Incompatibilities between the continuous SB function and the irregular and discrete nature of foliage distribution of single trees occasionally produced large prediction errors. Based on these results, the SB function fitted with the two-percentile method suitably describes the vertical distribution of leaf area of a wide variety of loblolly pine trees. FOR. SCI. 51(2):93–101.

Nitrogen Management in a Fraser Fir ( Abies fraseri [Pursh] Poir.) Christmas Tree Plantation: Effects of Fertilization on Tree Performance and Nitrogen Leaching - David E. Rothstein (Forest Science, 2005)
There is increasing concern over the effects of nitrogen (N) pollution resulting from fertilizer inputs to food and fiber production systems. Christmas tree production is one segment of the forestry sector that uses substantial fertilizer inputs. However, we know very little about the environmental costs and production benefits of N fertilization in Christmas tree plantations. I studied the costs and benefits of 2 years of N applications (as ammonium sulfate) at 0, 47, 95, and 140 kg N ha−1 year−1 to 4-year-old Fraser fir (Abies fraseri) Christmas trees. These rates correspond to 0, 50, 100, and 150% of the amount recommended for 4-year-old trees, and 33, 67, and 100% of recommendations for 5-year-old trees. There were no significant effects of fertilization rate on tree growth or morphology. In contrast, foliar N concentrations increased with increasing rates of N application, and there was a trend toward improved foliage health (indicated by chlorophyll fluorescence) at the lowest application rate. Mineral N (NH+4 + NO−3) concentrations in water leaching below the rooting zone increased markedly with increasing N application rates. Lysimeter NO−3 concentrations in the highest application treatment were consistently 20–30 times greater than the safe drinking water standard of 10 mg NO−3-N/l. Together, these results suggest that conventional guidelines for fertilization of Michigan Fraser fir plantations greatly exceed the capacity of trees and surface soils to store N, provide no benefit to tree growth, and create the potential for significant N pollution of ground and surface waters. Furthermore, these results indicate that applying N at a lower rate of 47 kg N ha−1 year−1 substantially reduced NO−3 leaching with no decline in growth rates or tree quality. FOR. SCI. 51(2):175–184.

Is There a Single National Lumber Market in the United States? - Runsheng Yin; Jungho Baek (Forest Science, 2005)
This article revisits the question of whether the law of one price (LOP) holds for the United States lumber markets, with the most disaggregate data and a large number of price combinations for different products, regions, and species. We also paid close attention to issues related to how we should conduct unit root tests with a potential structural break, whether we should include intercept and time trend in a co-integration model, and what lag length should be chosen. After exhaustive investigations, we find overwhelming evidence supporting the LOP for the entire United States softwood lumber market. We believe that this finding has profound implications on our market modeling and policy analysis. FOR. SCI. 51(2):155–164.

Optimum Juvenile Density, Harvesting, and Stand Structure in Even-Aged Scots Pine Stands - Kari Hyytiäinen; Olli Tahvonen; Lauri Valsta (Forest Science, 2005)
The economics of timber production is studied using empirical data for various juvenile densities and a distance-independent individual-tree growth model specified for Finnish Scots pine (Pinus sylvestris [L.]) stands. Our results imply that explicit inclusion of quality effects on prices increases optimum juvenile density. In addition, quality effects make economic surplus of forestry more sensitive to variations in juvenile density. Optimum thinnings remove trees that have no prospects for high relative value growth. Optimum thinnings are selective thinnings that remove inferior-quality trees, some of the smallest trees and, contrary to conventions, those of the largest trees that fulfill the sawlog dimensions. Thinnings removing trees strictly above and/or below certain tree diameters homogenize the remaining growing stock by narrowing the diameter distribution. Homogeneous stand structure is economically favorable at final clearcutting because the stand can be clearcut promptly after the majority of trees have reached sawlog dimensions and have experienced the last high peak in value growth. FOR. SCI. 51(2):120–133.

Screening European Elms for Resistance to Ophiostoma novo-ulmi - Alejandro Solla; Jürgen Bohnens; Eric Collin; Stephanos Diamandis; Albrecht Franke; Luis Gil; Margarita Burón; Alberto Santini; Lorenzo Mittempergher; Jean Pinon; An Vanden Broeck (Forest Science, 2005)
Resistance breeding of the native elms against Dutch elm disease, caused by the fungus Ophiostoma novo-ulmi Brasier, is a major objective in Europe for the conservation of this tree species. More than 2,500 cuttings of 324 elm clones (Ulmus minor Miller, U. glabra Huds., U. laevis Pall., U. pumila L., U. minor x U. glabra, and U. minor x U. pumila) from eight European countries, planted in several randomized two-block designed plots were inoculated with various O. novo-ulmi strains. Crown wilting and dieback were recorded during the first year after inoculation. The wilting of the control trees varied among the plots, making the results difficult to compare, but analysis of variance (ANOVA) within each plot showed significant differences in disease severity among the clones tested, allowing study of the variation of the response among elm taxa. Results showed that 19 European inoculated clones recovered from O. novo-ulmi attack, giving hope for the reestablishment of native elms in countryside hedges and forests. FOR. SCI. 51(2):134–141.

Correction (Forest Science, 2005)

Genotype by Environment Interactions in an Australia-Wide Radiata Pine Diallel Mating Experiment: Implications for Regionalized Breeding - Harry X. Wu; A. Colin Matheson (Forest Science, 2005)
Genotype by site interactions were studied in an Australia-wide diallel experiment covering 10 testing sites for stem dbh, stem straightness, branch angle and size, and number of branch clusters on the stem at age 10.5 to 11.5 years. The size and practical importance of genotype by site interactions were examined by four approaches: (1) the ratio of interaction variance to general combining ability (GCA) variance; (2) additive genetic correlations among sites; (3) testing whether the interaction was a result of a few families reacting more than others; and (4) by the size of genetic gains through a proposed regionalization. The genotype by site interaction for dbh observed in this experiment was larger than reported earlier for radiata pine because two high-elevation sites were included. There were more interactions between the two high-elevation sites and other lower elevation sites than interactions between lower elevation sites. The large genotype by region interaction was attributed to the extensive snow loading at the two higher elevation sites. Gain predictions from five regionalization schemes in this experiment favor regionalization of radiata pine breeding into two main regions: higher elevation and lower elevation sites. FOR. SCI. 51(1):29–40.

Developmental Pathways following the Harvest of Oak-Dominated Stands - Peter J. Gould; Kim C. Steiner; James C. Finley; Marc E. McDill (Forest Science, 2005)
The postharvest development of 90 formerly oak-dominated stands in Pennsylvania was examined to identify developmental pathways that led to a range of stand compositions and structures in the third decade after harvest. Operational data collected through the course of timber sale administration were used to quantify preharvest overstory composition and the distribution and composition of advance regeneration and regeneration 2 years after harvest. Stands were re-measured during their third decade of development. Based on their third-decade compositions, stands were grouped into four distinct classes. The development of each class was then traced by comparing preharvest overstory, advance regeneration, and postharvest regeneration compositions between classes. Stands in the OAK class maintained dominance by oaks throughout stand development, resulting in an average of 83.8% oak stocking in the third decade after harvest. Stands in the MIXED and RED MAPLE classes began with lower levels of advance oak regeneration and lost oak dominance relative to preharvest stand compositions. The MIXED class experienced recruitment of pioneer species after harvest, resulting in stands where black birch (Betula lenta L.) and other species are important components, despite being poorly represented as advance regeneration. The RED MAPLE class had abundant red maple (Acer rubrum L.) advance regeneration and lacked postharvest recruitment of oaks or pioneer species, leading to the development of red maple-dominated stands. Stands in the UNSTOCKED class suffered preharvest mortality and regeneration (primarily red maple) declined after harvest, resulting in regeneration failures. The four developmental pathways demonstrate the importance of specific stand conditions at the time of harvest and, to a lesser extent, just after harvest to future stand development. FOR. SCI. 51(1):76–90.

Nonparametric Tests for Profit Maximization with Incomplete Data: Application to the Pulp and Fine Paper Production in Finland - A. Maarit I. Kallio; Riitta Hänninen (Forest Science, 2005)
Forest sector models give relevant information to decision makers only if they are based on correct economic hypotheses. This requires that the data from which the model parameters are estimated are consistent with the a priori assumptions made on market agents' behavior and competition patterns. For static models, rather simple nonparametric tests exist for checking such consistency. Such tests also provide an analyst with insights on possible errors in the data and the suitability of the data for the particular econometric model that the analyst has in mind. This article proposes data tests for the competitive or noncompetitive profit-maximization hypothesis that can also be used with incomplete data. The tests are applied to quarterly data on the production of pulp and fine paper in Finland. It is found that the data may not represent profit-maximizing price takers. Although this can be due to, e.g., integrated production, missing dynamics, or noncompetitive behavior—a hypothesis that was indeed found to be consistent with the fine paper data—it is evident that the modeler should not use these data in estimating a parametric industry model that builds on price-taking profit-maximizing behavior. The results emphasize the importance of testing the data before modeling. FOR. SCI. 51(1):19–28.

Management of Mixed-Species, Uneven-Aged Forests in the French Jura: From Stochastic Growth and Price Models to Decision Tables - François Rollin; Joseph Buongiorno; Mo Zhou; Jean-Luc Peyron (Forest Science, 2005)
A deterministic matrix growth model of uneven-aged stands of fir, spruce, and hardwood trees was extended to recognize random shocks. The results showed that the expected basal area of hardwoods, mainly beech, was substantially higher in the long run than that predicted by the deterministic model. A parallel stochastic model of prices was also developed from past data. It showed that real prices had no trend but that they were autocorrelated over time. The stochastic stand and price models were simulated simultaneously to obtain the probabilities of transition between stand and market states. This transition probability matrix was used in Markov decision-process models to calculate the best decision in each possible stand and market state. The policies examined included maximizing net present value, or expected tree diversity, production, or annual returns, subject to constraints on net present value, expected tree diversity, and basal area. A general mathematical programming method is presented to optimize economic or ecological objective functions subject to multiple constraints with or without time discounting. In the French Jura context, the solutions suggested that high net present value could be obtained while maintaining the average basal area near its current level, and keeping a high level of tree diversity. Accounting for risk called for more intense harvesting to raise revenues, and it led to stands that were much more diverse than suggested by deterministic solutions. FOR. SCI. 51(1):64–75.

Tree Density Estimations Using a Distance Method in Mali Savanna - Nicolas Picard; Amadou M. Kouyaté; Hélène Dessard (Forest Science, 2005)
The biological characteristics of trees in tropical dry savannas make it difficult to conduct inventories of tree density, and this has aroused interest in distance-based methods. This study proposes a distance-based tree density estimator using Matérn point processes, generating clustered spatial patterns. It was defined as the maximum likelihood estimator of the density, based on an approximate distribution of the distance from a random point to the pth nearest tree. It was compared with seven estimators identified in the literature as the most efficient. The estimators were compared on a benchmark of 10 point processes, with six being adjusted to observed tree patterns in six Mali savannas (West Africa). The proposed estimator was generally the most efficient. However, this result ignores that (i) all estimators do not require the same effort on the field, (ii) the point-processes benchmark was restricted to Matérn processes, and (iii) all estimators are not equivalent with respect to measurement errors. FOR. SCI. 51(1):7–18.

Forest Fragmentation Estimated from Remotely Sensed Data: Is Comparison Across Scales Possible? - Soledad García-Gigorro; Santiago Saura (Forest Science, 2005)
Remotely sensed data with different spatial resolutions are being used as the primary information source for the analysis of forest fragmentation. However, there is currently a lack of appropriate methods that allow for the comparison of forest fragmentation estimates across various spatial scales. To provide insights into this problem we analyzed a forested study area in central Spain and a set of 10 widely used fragmentation indices. Forests were mapped from two simultaneously gathered satellite images with different spatial resolutions, 30 m (Landsat-TM) and 188 m (IRS-WiFS). TM forest data were transferred to WiFS resolution through different aggregation rules and compared with actual WiFS data. We found that incorporating sensor point spread function (which replicates the real way in which remote sensors acquire radiation from the ground) greatly improved comparability of forest fragmentation indices. We found a poor performance of power scaling laws for estimating forest fragmentation at finer spatial resolutions, and suggest that the true accuracy and practical utility of these scaling functions may have been overestimated in previous literature. Finally, we report an unstable behavior of three cell-based fragmentation indices (clumpiness, aggregation, and patch cohesion indices), for which spuriously high values can be obtained by resampling forest data to finer spatial resolutions. We believe that the results and guidelines provided may significantly contribute to an adequate analysis and comparison across scales of forest fragmentation estimations. FOR. SCI. 51(1):51–63.

Improved Estimation for Multiple Means with Heterogeneous Variances - Edwin J. Green; William E. Strawderman; Ralph L. Amateis; Gregory A. Reams (Forest Science, 2005)
Two new estimators are presented for use in situations where simultaneous estimation of more than two sample means is required and alternative, possibly biased information is available. The new estimators are modifications to an older estimator by Green and Strawderman. The latter estimator assumed homogeneous variances, whereas the new ones are designed for the more usual case of heterogeneous variances among the sample means. In simulation experiments, the new estimators yielded superior performance to that of the ordinary sample mean vector (X). Surprisingly, the estimator designed to dominate X under precision-weighted loss was apparently the best estimator, even under nonprecision-weighted loss. Use of the new estimators should allow foresters to achieve considerable savings in estimation precision. FOR. SCI. 51(1):1–6.

Trees, Crops and Soil Fertility: Concepts and Research Methods - J. Doland Nichols (Forest Science, 2005)
Up until about 20 years ago, agroforestry literature was generally vague and descriptive–“trees are good and farmers and graziers should plant more of them.” Existing systems, especially ones developed in the tropics, were described, but usually not systematically studied, and an overall optimism about the benefits of trees on farms prevailed. Many years were spent in international research and development projects promoting “agroforestry,” particularly the use of nitrogen-fixing, multiple-use (products and services) trees, especially Leucaena leucocephala. Often farmers have not taken up the recommended systems. Although they may not have phrased it in academic language, their basic objections were something like, “aggressive fast-growing trees will take up space and compete with crops or pasture for water, nutrients, or light; and the benefit-to-cost ratio, at least in the short term, is not favorable.”

A Critical Evaluation of Fire Suppression Effects in the Boreal Forest of Ontario - S.R.J. Bridge; K. Miyanishi; E.A. Johnson (Forest Science, 2005)
Although fire suppression is widely believed to have changed the “natural” fire regime in the boreal forest, empirical evidence for this effect is limited and usually involves a comparison of fire sizes, average annual area burned, and fire cycle between areas with and without fire suppression. We critically evaluate this empirical evidence and discuss problems with untested assumptions, data quality, statistical analyses, interpretations, and inferences. Furthermore, to test the hypothesis that fire suppression has changed the natural fire regime, we apply time-since-fire techniques to spatial fire data (1921–1995) for the western and eastern boreal regions of Ontario and compare temporal and spatial variation in fire cycle for areas with and without fire suppression. There is no detectable temporal change in fire cycle between 1921 and 1995 in areas with aggressive fire suppression; however, interpretation of the fire cycle in areas without aggressive fire suppression is confounded by insufficient data. Also, although the western region shows an increase in fire cycle from fully protected to less protected areas, the eastern region shows the shortest fire cycle in the most protected area. Thus, to date there is insufficient empirical evidence that fire suppression has significantly changed the fire cycle in the boreal forest of Ontario. FOR. SCI. 51(1):41–50.

Author and Subject Index (Forest Science, 2004)

Sap Beetle Species (Coleoptera: Nitidulidae) Visiting Fresh Wounds on Healthy Oaks During Spring in Minnesota - Jennifer Juzwik; Thomas C. Skalbeck; Marc F. Neuman (Forest Science, 2004)
Many species of sap beetles have been implicated as vectors of the oak wilt pathogen, (Ceratocystis fagacearum), but the species responsible for most aboveground transmission of the fungus is unknown. The abundance of adult sap beetle species inhabiting <7-day-old, artificially made wounds on healthy oaks during Apr.–June of 2 years in Minnesota, and the frequencies with which viable propagules of the fungi were present on each, were determined. Sap beetles were most abundant on wounds created in May, and 1–3-day-old wounds yielded higher numbers of insects than 4–6-day-old wounds. Of the beetles collected, >95% were Colopterus truncatus and Carpophilus sayi. C. fagacearum was isolated from 75% of 594 adults assayed for the fungus. The average number of viable propagules for pooled data of individuals of each species ranged from <100 to 18,000. Frequencies of fungus isolation differed by days after wounding, study location, and sap beetle species. These results, when coupled with previous findings on predominant species associated with oak wilt fungi mats, support the hypothesis that Co. truncatus and Ca. sayi are the principal sap beetle species transmitting C. fagacearum from diseased to healthy oaks in Minnesota. FOR. SCI. 50(6):757–764.

The Two-Stage Method for Measurement Error Characterization - Sean J. Canavan; David W. Hann (Forest Science, 2004)
A measurement error (ME) is a component of any study involving the use of actual measurements, but is often not recognized or is ignored. The consequences of ME on models can be severe, affecting estimates of tree and stand attributes and model parameters. Although correction methods do exist for countering the effects of ME, the use of these methods requires knowledge of the distribution of the errors. A new method for modeling error distributions, called the two-stage error distribution (TSED) method, is presented here. This method is compared with traditional methods for error modeling through an example using diameter and height ME. Comparisons between the fitted error distribution surfaces and the empirical error surface are based on a dissimilarity measure. The results indicate that the TSED method produces a much more accurate and precise characterization of the ME distribution than do traditional methods when a high percentage of errors is identical. In other cases, the TSED method works as well as the most accurate form of the traditional method. The TSED method is also expected to perform better at characterizing asymmetric distributions. It is therefore more adaptable than traditional methods and is being proposed for error modeling in the future. FOR. SCI. 50(6):743–756.

Book Reviews: Toward Forest Sustainability - Scott D. Roberts (Forest Science, 2004)
A major issue facing forestry these days is whether forests can be actively managed while supporting diversity and maintaining their natural range of ecological processes and functions. In other words, can forests be managed sustainably? This book contains a collection of essays written by participants of a sustainable forestry roundtable held in 2002 in Marysville, Victoria, Australia. Although much of the conference focused on Australia's montane ash forests, the purpose of the book is to share the wisdom and experience of experts from countries throughout the temperate regions of the world as their countries struggle to learn how to manage forests more sustainably in the face of changing political and environmental pressures. Some of the contributors will be very familiar to readers who have followed the sustainable-forest management debates in North America, including Jerry Franklin, Michael Soulé, David Perry, and Frank Bunnell. Other contributors may not be as familiar to the North American audience, but will certainly be recognized by those who have followed the international sustainable-forestry debate. These include, among others, David Lindenmayer and Per Angelstam.

Book Reviews: Analysis of Ecological Communities - John J. Battles (Forest Science, 2004)
As an aspiring student in forest ecology, I was never more distressed about my career choice than when a senior graduate student predicted that I would spend more time learning statistics than any other subject. Twenty years later, the contents of my bookshelf and hard drive provide compelling evidence of the truth of this prediction. Community ecology has collected an eclectic mix of multivariate techniques to quantify the relationships among species and their environment. The challenge has always been to sort through the lot to find the most appropriate approach given the question and the data. While I still sometimes pine for the simplicity of a two-way analysis of variance (ANOVA), Bruce McCune and James Grace's book, Analysis of Ecological Communities satisfies my craving for statistical clarity. They provide an exemplary guide to the convoluted terrain of multivariate data analysis.

Are Self-Thinning Constraints Needed in a Tree-Specific Mortality Model? - Robert A. Monserud; Thomas Ledermann; Hubert Sterba (Forest Science, 2004)
Can a tree-specific mortality model elicit expected forest stand density dynamics without imposing stand-level constraints such as Reineke's maximum stand density index (SDImax) or the −3/2 power law of self-thinning? We examine this emergent properties question using the Austrian stand simulator PROGNAUS. This simulator was chosen specifically because it does not use stand density constraints to determine individual tree mortality rates. In addition, it is based on a probability sample of the population that includes the span of the data being used to test the hypothesis. Initial conditions were obtained from 27 permanent research plots that were established in young pure stands of Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) in Austria. A growth period of 250 years was simulated. We conduct our test in two parts. First, we compare our simulated results to Reineke's theory of maximum density and stand density index by examining the self-thinning relationship between stem number per hectare and quadratic mean diameter (log-log scale). Second, we compare our results to Sterba's full competition density rule, which incorporates dominant height along with stem number and quadratic mean diameter. From the results for Norway spruce, we conclude that stand-level density constraints are not necessary to obtain Reineke's maximum size-density relations. Norway spruce results confirm that the maximum size-density relationship reflects reasonable and stable stand dynamics and conforms to that expected by Reineke's theory. Results from simulation of Scots pine also display reasonable and stable stand dynamics, except that they greatly exceed Reineke's maximum stand density index determined empirically from the literature. This Scots pine result argues for stand-level constraints (such as specifying SDImax) to ensure that the appropriate intercept for the maximum density line is used. Our second test revealed that the estimated maximum stand density index according to Sterba's theory was too high for both species, but that the relative rankings across plots were correct. Thus, we are left with ambiguous results. First, that a density-dependent individual-tree mortality model, developed on an adequate data set, is sufficient for the desired stand-level behavior of Reineke to emerge. Second, that stand-level constraints on SDImax need to be imposed if the underlying mortality modeling database is not adequate. FOR. SCI. 50(6):848–858.

Predicting the Spatial Distribution of Leaf Litterfall in a Mixed Deciduous Forest - Jeroen Staelens; Lieven Nachtergale; Sebastiaan Luyssaert (Forest Science, 2004)
An accurate prediction of the spatial distribution of litterfall can improve insight in the interaction between the canopy layer and forest floor characteristics, which is a key feature in forest nutrient cycling. Attempts to model the spatial variability of litterfall have been made across forest types, but the reported models have not yet been compared. We predicted the spatial distribution of leaf litterfall for the same mixed hardwood stand using inverse distance interpolation, ordinary kriging, single and multiple regressions based on plot basal area, and three individual-tree models. Models were calibrated using litterfall data (n = 67) of white birch (Betula pendula Roth), pedunculate oak (Quercus robur L.), and northern red oak (Quercus rubra L.). Model performance was compared using an independent validation data set (n = 37). Interpolation techniques did not reliably estimate spatial patterns of leaf litterfall (r < 0.60, n = 37). However, models incorporating tree data, such as linear regressions and individual-tree models, successfully reproduced the observed spatial litterfall heterogeneity of each species (r > 0.80). No model was able to predict the variability of the total leaf litterfall of the three species. We conclude that, for an intimately mixed forest stand, a model that simulates leaf dispersal of individual trees is likely to be the best choice for predicting the spatial distribution of leaf litterfall. FOR. SCI. 50(6):836–847.

Young Stand Growth Modeling for Intensively-Managed Loblolly Pine Plantations in Southeastern U.S - James A. Westfall; Harold E. Burkhart; H. Lee Allen (Forest Science, 2004)
Intensively managed loblolly pine stands are often subjected to a variety of silvicultural treatments at time of planting or shortly thereafter. However, most loblolly pine growth-and-yield models predict growth after crown closure has occurred. In this article, we describe the development and implementation of a system of equations designed to simulate growth of loblolly pine before the onset of intraspecific competition. Treatment response functions were also developed for various site preparation, herbaceous weed control, and fertilization practices. These functions modify the baseline model predictions to simulate the effects of treatments on tree growth and stand development. This system was incorporated into the PTAEDA2 growth-and-yield simulator to make growth projections from time of planting through rotation age for intensively managed stands of loblolly pine in the southeastern United States. Growth simulations specifying either bedding or disking showed increases in volume growth for both treatments. The shear-and-pile site-preparation method reduced growth rates slightly. Volume growth responses to herbaceous weed control were positive, with magnitude of increase largely depending on duration of treatment. Increases in volume attributable to fertilization at planting were related to types of element applied. The largest predicted response was for phosphorus fertilization, whereas application of potassium was the least effective fertilization treatment. Site preparation, weed control, and fertilization treatment combinations produced additional volume gains when compared to single treatments, while maintaining predicted values that are within biological limits for loblolly pine growth. Levels of response to treatments are consistent with results from published studies on intensive management practices. The addition of the precompetitive growth system did not significantly affect the predictive behavior of the PTAEDA2 model for untreated stands. FOR. SCI. 50(6):823–835.

A Pòlya-Urn Resampling Scheme for Estimating Precision and Confidence Intervals Under One-Stage Cluster Sampling: Application to Map Classification Accuracy and Cover-Type Frequencies - Steen Magnussen; Stephen V. Stehman; Piermaria Corona; Michael A. Wulder (Forest Science, 2004)
A Pòlya-urn resampling scheme (PURS) is introduced as an alternative to classical inference (CLAS) for applications related to map accuracy and estimating cover-type frequencies from land-cover maps. PURS is akin to a Bayesian bootstrap procedure for generating a predictive posterior distribution of sample estimates. PURS is a simple alternative to the complexity of deriving Taylor-series approximation (TSA) to CLAS variance estimators and reliance on asymptotic normality for construction of confidence intervals. The potential advantages of the resampling scheme are explored in simulated sampling of actual data from three 102–107-km2 large study sites. PURS root mean square errors (rmse) of six measures of classification accuracy were slightly lower than TSA to CLAS rmse. PURS estimated standard errors and coverage rates of confidence intervals (95%) for bias-corrected classified cover-type frequencies were, in most cases, superior to corresponding TSA. Yet variance estimators and confidence intervals constructed for a cover type occupying less than 5% of a study site were consistently underestimated by both methods. PURS is adaptable to a wide range of forest resource survey designs. FOR. SCI. 50(6):810–822.

Photosynthetic and Water Use Efficiency Responses to Diffuse Radiation by an Aspen-Dominated Northern Hardwood Forest - Adrian V. Rocha; Hong-Bing Su; Christoph S. Vogel; Hans Peter Schmid; Peter S. Curtis (Forest Science, 2004)
Clouds can exert strong effects on ecosystem CO2 and water vapor fluxes and may be important determinants of terrestrial primary production. We used three years of eddy-covariance and meteorological data from an aspen-dominated northern hardwood forest in Michigan to investigate how canopy photosynthesis (P), evapotranspiration (E), and water use efficiency (WUE) responded to changes in cloud cover, or the proportion of diffuse (If) to total (It) photosynthetically active radiation (PAR). Canopy quantum efficiency (the initial slope of the P versus PAR response curve) increased with increasing cloud cover, but both midday canopy P and canopy photosynthetic potential (the asymptote of the P versus PAR response curve) were greatest under partly cloudy skies (If/It = ∼0.57). Midday canopy E decreased and midday canopy WUE increased with increasing If/It. The relationship between canopy P and cloud cover varied with soil moisture. Canopy P was insensitive to changes in soil moisture under overcast skies (If/It > 0.70), whereas under clearer skies, canopy P was lower during periods of low compared to high soil moisture. These results further our understanding of cloud cover effects on canopy physiological processes and will aid in more accurate assessments of forest responses to climatic change. FOR. SCI. 50(6):793–801.

Coarse Woody Debris in Managed Central Hardwood Forests of Indiana, USA - Michael A. Jenkins; Christopher R. Webster; George R. Parker; Martin A. Spetich (Forest Science, 2004)
We evaluated the volume of down deadwood (DDW) and the basal area of standing deadwood (SDW) from a chronosequence of 110 silvicultural openings and 34 mature stands (72–105 years old) across three Ecological Landtype Phases (ELTP; wet-mesic bottomlands, mesic slopes, and dry-mesic slopes) in southern Indiana, USA. The volume of DDW decreased with increasing opening age and was lower in clearcuts than in group-selection openings. Openings on mesic slopes and bottoms contained greater volumes of DDW than openings on dry-mesic slopes. Regardless of age and ELTP, openings contained low volumes of highly decayed DDW. The volume of small-diameter DDW decreased rapidly with increasing stand age across all three ELTPs. Mature stands contained low total volumes of DDW (maximum of 22.4 ± 5.1 m3 ha−1) and low volumes of both highly decayed and large-diameter DDW. Most of the dead trees in silvicultural openings were small diameter and did not contribute significantly to DDW volume. SDW basal area was very low in mature stands (maximum of 1.4 ± 0.5 m2 ha−1), suggesting that little mortality has occurred. Our results suggest that even and uneven-aged silviculture in hardwood forests have differing impacts on the volume and distribution of coarse woody debris (CWD). In addition, the mature stands that dominate forests across much of the Central Hardwood Region of the eastern United States contain relatively little CWD compared to younger and old-growth stands. FOR. SCI. 50(6):781–792.

Modeling Nesting Habitat Selection of California Spotted Owls ( Strix occidentalis occidentalis ) in the Central Sierra Nevada Using Standard Forest Inventory Metrics - Monica L. Bond; Mark E. Seamans; R. J. Gutiérrez (Forest Science, 2004)
California spotted owl (Strix occidentalis occidentalis) nest sites are associated with large trees, moderate-to-high tree densities, high canopy cover, and structural complexity. Therefore, forest managers need accurate estimates of these characteristics. Standard forest inventory metrics, such as those estimated from Forest Inventory and Analysis (FIA) data, are used by silviculturists to assess forest trends and condition, and are a source of data for assessing wildlife habitat. We estimated which FIA metrics best predicted California spotted owl nesting habitat by developing a nesting-habitat model comparing owl nest stands with randomly chosen forest stands in potential nesting habitat (stands dominated by 30–60.9- and ≥61-cm diameter trees and ≥40% cover) in the central Sierra Nevada. Number of large trees (≥76.2 cm) and canopy cover were the best predictors of owl nesting habitat. We present a nesting-habitat selection model based on our analysis. FIA metrics may be useful for quantifying California spotted owl habitat in our study area, but because forest conditions are highly variable in the Sierra Nevada, our results should be tested further in other geographic regions. FOR. SCI. 50(6):773–780.