Salamander Abundance and Amphibian Species Richness in Riparian Buffer Strips in the Oregon Coast Range - David G. Vesely; William C. McComb (Forest Science, 2002)
Logging and other forest practices are widely reported to be a threat to some amphibian populations in the Pacific Northwest. Riparian buffer strips are one conservation measure that may benefit amphibians in managed forests. However, few amphibian surveys have been conducted in buffer strips. We compared total salamander abundance, amphibian species richness, and sampling proportions for five species of salamanders between 17 managed stands and 12 unlogged, streamside forests in the Coast Range of western Oregon. We also identified relationships between buffer strip width and salamander population indices. Surveys conducted on 20 × 40 m plots demonstrated that torrent salamanders (Rhyacotriton spp.), clouded salamanders (Aneides ferreus), Dunn's salamanders (Plethodon Dunni), western red-backed salamanders (Plethodon vehiculum), total salamander abundance, and amphibian species richness were sensitive to forest practices in riparian areas. We conclude that riparian buffer strips are a useful habitat management strategy for several salamander species. However, buffer strip widths currently required by state forest practices regulations may not be adequate to prevent local declines in the diversity of amphibian communities. FOR. SCI. 48(2):291–297.

Wildlife-Habitat Relationships in Oregon and Washington - Richard M. DeGraaf (Forest Science, 2002)
This is a massive compilation that greatly expands on the coverage and regional themes introduced in the epochal Wildlife Habitat Relationships in Managed Forests: the Blue Mountains of Oregon and Washington (1979. J.W. Thomas, tech. coord., Pacific Northwest Forest and Range Experiment Station, USDA Forest Service, Portland, OR), Management of Wildlife and Fish Habitats in Forests of Western Oregon and Washington (1985. E.R. Brown, tech. ed., Pacific North-west Region, USDA Forest Service, Portland, OR), and Atlas of Oregon Wildlife (1997. B. Csuti, et al., Oregon State University Press, Corvallis, OR). The much-litigated natural resources management plans in the Pacific Northwest have focused attention on a few species, largely in mixed conifer forests. But the region is very diverse, and the current work covers the entire range of vegetative communities, from eastern shrubsteppe and agriculture, interior forests, westside grasslands and chaparral, to riparian, coastal, and marine environments, in addition to the more familiar mixed conifer forests.

The Effect of Forest Roads on the Reproductive Success of Forest-Dwelling Passerine Birds - David I. King; Richard M. DeGraaf (Forest Science, 2002)
Recent studies indicate that forest roads may affect the distribution of forest-dwelling birds. However, previous studies have not demonstrated any significant effects of forest roads on avian productivity. We studied the effect of maintained and unmaintained forest roads on (1) forest bird nest survival, (2) reproductive parameters of ovenbirds (Seiurus aurocapillus) potentially associated with food abundance, and (3) habitat and microclimate at six sites on the White Mountain National Forest, New Hampshire, during two breeding seasons. Nest survival did not differ between areas near (0–150 m) and far (>150 m) from maintained forest roads, and was marginally (P=0.08) higher in areas near (0–150 m) unmaintained roads. When the 0–150 m distance class was subdivided, however, nest survival was significantly higher within 0–75 m of maintained roads than >75–150 m away. Ovenbird nest initiation dates, clutch size, and fledging success did not differ between areas near (0–150 m) and far (>150 m) from maintained and unmaintained forest roads, and this result did not change when the distance class 0–150 m from roads was subdivided. There were no relationships between habitat or microclimate and distance from maintained roads. We conclude that small, unsurfaced forest roads at low road density do not result in decreases in forest passerine bird productivity in extensively forested areas in New England. FOR. SCI. 48(2):391–396.

Reproduction of Amphibians in Natural and Anthropogenic Temporary Pools in Managed Forests - Danielle DiMauro; Malcolm L. Hunter (Forest Science, 2002)
Vernal-pool breeding amphibians often oviposit in anthropogenic pools formed during industrial forest-management activities, as well as in natural ephemeral pools. We quantified wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) reproductive effort and metamorph emergence, pool hydroperiods and environmental features, and the density of natural and anthropo-genic pools across the landscape to compare the reproductive effort and success of amphibians breeding in natural and anthropogenic pools in managed forests in Maine. Numbers of egg masses in anthropogenic and natural pools did not differ for either wood frogs (median number masses/pool = 15 and 14, respectively) or spotted salamanders (13 and 13 masses/pool). Anthropogenic pools outnumbered natural pools on survey transects by a factor of 3.7. Pool area, depth, temperature, solar exposure, and coverage of closed-canopy forest within 100 m influenced amphibian reproductive effort in temporary pools. In a year with typical breeding-season rainfall (1997), anthropogenic pools dried sooner than natural pools (median drying dates: June 17 and July 30, respectively), and extensive larval mortality occurred upon pool drying. During an unusually wet breeding season (1996), the two pool types had similar hydroperiods (median drying dates: August 17 and 28). Metamorphs emerged from natural pools later and at larger size than metamorphs emerging from anthropogenic pools. Anthropogenic pools seem to function as ecological traps for breeding wood frogs in most years, and thus they should be avoided or designed with adequate size, depth, and shading to maintain an adequate hydroperiod. FOR. SCI. 48(2):397–406.

The Effects of Shelterwood Logging on Bird Community Composition in the Black Hills, Wyoming - Stanley H. Anderson; Bradley J. Crompton (Forest Science, 2002)
The Black Hills of Wyoming and South Dakota are characterized by a complex history of both natural and human disturbance regimes. Historically, ponderosa pine (Pinus ponderosa) communities were characterized by frequent, cool ground fires. Intensive fire suppression and timber harvest throughout the past century have drastically altered the structure of existing forests. Today, much of the area has been harvested using shelterwood logging resulting in open even-aged stands. The goal of this study was to compare bird communities in treated (areas that have recently been harvested) and untreated (areas receiving minimal silvicultural treatment) in the past 40 yr. Of the 20 commonly observed bird species, 3 species [red-breasted nuthatch (Sitta Canadensis), brown creeper (Certhia Americana), and ovenbird (Seiurus aurocapillus)] were conspicuously less abundant in treated than in untreated stands. Eleven other species were more abundant in treated stands, while six species showed no response to treatment. Although bird species diversity and the abundance of birds were highest in treated stands, this does not imply that logging is beneficial to the entire bird community. The abundance of particular bird species may appear to have increased, but the composition of the bird community has been altered. As more of the forested areas are harvested, the bird community will shift from one with birds typical of both open pine and dense pine forest to one dominated by ground foraging species. FOR. SCI. 48(2):365–372.

Roads as Edges: Effects on Birds in Forested Landscapes - Yvette K. Ortega; David E. Capen (Forest Science, 2002)
Numerous studies have documented that forest edges affect habitat use and reproductive success of forest birds, but few studies have considered edges created by narrow breaks in the forest canopy. We compared predation rates on artificial nests placed within forest habitat along edge transects, 10 m from unpaved roads, and along interior transects, 300 m from forest-road boundaries. Local factors, such as nest concealment, and landscape factors, such as the degree of forestation in surrounding areas, were accounted for when testing for edge effects on nest predation. We conducted fixed-radius point counts to compare relative abundance of 34 bird species on edge and interior transects. Also, seven study plots were established adjacent to unpaved roads to map the distribution of bird territories within edge areas, 0–150 m from unpaved roads, and interior areas, 150–300 m from roads. Rates of nest predation on artificial nests did not differ between edge and interior transects, but the distribution of forest birds was influenced by unpaved roads. Four of 18 forestinterior species had lower relative abundance or territory density adjacent to roads, while four of six species categorized as edge nesters had higher relative abundance on edge transects. Our results suggest that narrow openings within forested landscapes may affect habitat use but not nest predation levels, emphasizing the need to frame definitions of “edge effects” within the context of multiple ecological processes. FOR. SCI. 48(2):381–390.

Herpetofaunal Response to Gap and Skidder-Rut Wetland Creation in a Southern Bottomland Hardwood Forest - Robert B. Cromer; Joseph D. Lanham; Hugh H. Hanlin (Forest Science, 2002)
We compared herpetofaunal communities in recently harvested gaps, skidder trails, and unharvested depressional wetlands to assess the effects of group-selection harvesting and skidder traffic on reptiles and amphibians in a southern bottomland hardwood forest. From January 1, 1997 to December 31, 1998 we captured 24,292 individuals representing 55 species of reptiles and amphibians at the Savannah River Site in Barnwell County, South Carolina. Forty-two species (n = 6,702 individuals) were captured in gaps, 43 species (n = 8,863 individuals) were captured along skid trails between gaps and 43 species (n = 8,727 individuals) were captured in bottomland depressions over the 2 yr period. Three vegetation variables and six environmental variables were correlated with herpetofaunal abundance. Salamander abundance, especially for species in the genus Ambystoma, was negatively associated with areas with less canopy cover and pronounced rutting (i.e., gaps and skidder trails). Alternatively, treefrog (Hylidae) abundance was positively associated with gap creation. Results from this study suggest that group selection harvests and skidder rutting may alter the herpetofaunal species composition in southern bottomland hardwoods by increasing habitat suitability for some species while diminishing it for others. FOR. SCI. 48(2):407–413.

Effects of Landscape and Local Habitat Attributes on Northern Goshawk Site Occupancy in Western Washington - Sean P. Finn; John M. Marzluff; Daniel E. Varland (Forest Science, 2002)
We quantified habitat structure, composition, and configuration at three spatial scales (39 ha nest area; 177 ha post-fledging area; 1,886 ha home range) and compared vegetative conditions with measures of northern goshawk (Accipiter gentilis) site occupancy at 30 historical nest sites (those containing at least one goshawk and a large stick nest when discovered) on Washington's Olympic Peninsula. Twelve of the 30 historical sites were occupied by one or more goshawks and 8 of the 12 contained a successful breeding pair. Sites that were occupied in 1 yr tended to remain occupied throughout the 3 yr study, and breeding success was strongly and positively correlated with occupancy. Occupied historical sites tended to have a high proportion of late-seral forest [>70% canopy closure of conifer species with >10% of the canopy trees >53 cm diameter at breast height (dbh)], reduced stand initiation cover, and reduced landscape heterogeneity at all three scales, but only the two larger scale models predicted occupancy successfully. Incorporating habitat attributes previously measured at finer (stand level) scales (canopy depth and percent shrub cover in the nest stand) improved our larger (landscape level) scale models of goshawk occupancy. Olympic Peninsula forest managers can promote goshawk occupancy, and therefore reproduction, by limiting the amount of early forest stand initiation cover (<20%) and landscape contrast in the home range and by maintaining potential nest stands (≥39 ha) having deep canopies and reduced shrub cover. FOR. SCI. 47(3):427–436.

Roost Site Characteristics of Northern Spotted Owls in the Nonbreeding Season in Central Washington - Dale R. Herter; Lorin L. Hicks; Henning C. Stabins; Joshua J. Millspaugh; Amy J. Stabins; Larry D. Melampy (Forest Science, 2002)
To evaluate habitat important to northern spotted owls (Strix occidentalis caurina) away from the nest stand, we used radio telemetry to locate adult owls at diurnal roosts during the nonbreeding season (September 1–March 15, 1994–1997). We recorded physiographic variables and measured within-stand structural characteristics within nested circular plots centered on roost trees. We then compared owl use plots to random plots selected within suitable habitat and inside the approximated home ranges of the 14 (7 male, 7 female) owls studied. Spotted owls selected older forest over young forest. Owls selected sites lower in elevation, with larger tree diameter at breast height (dbh), fewer trees/ha, greater canopy cover, less cover of low shrubs, and fewer pieces of down wood than random locations. Females used old-growth and mature forest to a greater degree than males. Fewer trees/ha, less cover of low shrubs, and fewer pieces of down wood/transect best discriminated roost sites from random sites. These characteristics are not indicative of stand conditions thought to maximize prey density. Results may indicate selection of specific sites for roosting. However, because spotted owls opportunistically take prey from diurnal roosts and often roost in foraging stands, they may also be selecting for site characteristics that facilitate the capture of prey. FOR. SCI. 48(2):437–444.

Evaluation of a Winter Habitat Suitability Index Model for Elk in West-Central Alberta - Paul F. Jones; Robert J. Hudson; Daniel R. Farr (Forest Science, 2002)
We evaluated a habitat suitability index (HSI) model developed to assess impacts of forestry on elk (Cervus elaphus) winter range in west-central Alberta. The HSI model consisted of 3 submodels that collectively utilized 14 habitat variables to represent the life requisites of food, thermal cover, and hiding cover. We assessed the performance of each submodel by determining if there was a positive correlation between a preference index (PI) and HSI classes and by determining if there was a significant difference in mean HSI for sites selected by elk versus mean HSI for available habitat sites. We used stepwise logistic regression to determine which habitat variables significantly differentiated used and available habitat sites. All 3 submodels in the original model performed poorly. Of the 20 habitat variables entered, stepwise logistic regression identified only 3 as important in differentiating elk feeding sites from available sites: tree height, stem density, and distance to unimproved access. Performance of the food submodel was improved when these 3 habitat variables and their logistic relationships were applied. Only stem density significantly differentiated elk bedding sites from available sites, but using only stem density and its logistic relationship did not improve performance of the cover submodels. Our approach to testing the model involved separating HSI scores for used and available sites, and is an alternative method to using population data. FOR. SCI. 48(2):417–425.

Floristics and Avian Community Structure: Implications for Regional Changes in Eastern Forest Composition - Amanda D. Rodewald; Marc D. Abrams (Forest Science, 2002)
Because many forest stands are increasingly dominated by maple (Acer spp.) in eastern North America, there will likely be a relative scarcity of mature oak (Quercus spp.) forests within the next several decades. In an effort to understand how avian communities may be affected by a regional change in forest composition from oak to maple dominance, we compared bird communities in both oak- and maple-dominated forest stands in three seasons (winter, spring, and fall). In 1998 and 1999, birds were surveyed and habitat characteristics were measured in six mature forest woodlots in central Pennsylvania. Total abundance of birds was greater within oak- than maple-dominated stands in all seasons, whereas species richness was greater in oak stands only in the spring. Resident species, long-distance migrants, woodpeckers, bark-gleaners, and 11 individual species were more abundant within oak than maple stands in at least one season. Differences in avian community structure between oak and maple stands were greatest in the fall when oaks produced hard mast and in the spring when insectivorous birds gleaned arthropods from tree substrates. This pattern was consistent with our expectations based on mast characteristics and tree physiognomy of maples and oaks as well as the diet and foraging behavior of birds. Our results suggest that a regional change from oak- to maple-dominated forests may strongly affect avian community structure and populations of some common bird species associated with eastern deciduous forests. FOR. SCI. 48(2):267–272.

Small Mammal Habitat Associations at Patch and Landscape Scales in Oregon - Karl J. Martin; William C. McComb (Forest Science, 2002)
To investigate multiscale habitat associations, we examined patterns of capture rates of small mammals in thirty 250–300 ha landscapes in the central Oregon Coast Range. We compared capture rates of 14 species within ≥7 patch types to expected capture rates based on sampling effort. We used landscape level capture rates to test for associations with percent area (composition) and 8 pattern indices at the landscape scale. Capture rates of 10 of 14 small mammal species were higher in conifer and/or mixed large sawtimber patch types. At the landscape scale, capture rates of 6 of 14 species of small mammals were positively associated with the area of patch types. The pattern of patches on the landscape may influence the distribution of 5 small mammal species in this region. We conclude that some small mammals may respond to landscape pattern and/or composition, while other small mammals may not respond to either landscape pattern or composition. Our results suggest that mature forest habitat, patch richness, pattern, and composition are key landscape features that should be considered in management plans, particularly when biodiversity of forest floor mammals is a management objective. FOR. SCI. 48(2):255–264.

Avian Habitat Relationships at Multiple Scales in a New England Forest - Sean W. MacFaden; David E. Capen (Forest Science, 2002)
Habitat selection by birds is a complex phenomenon that varies by species and ommunity. Some birds select habitat according to specific combinations of microhabitat characteristics, which pertain to the structure and composition of site-specific vegetation. Recently, however, habitat selection studies have shifted from site-specific characteristics to consideration of coarser environmental scales. We examined habitat relationships for 31 bird species in the White Mountain National Forest at a series of scales from microhabitat (fine scale) to the landscape (coarse scale). Relative abundance data were collected through 10 min. point counts at 360 points organized into 15 transects. Habitats sampled included a diversity of forest-cover types (deciduous to coniferous) and management strategies (wilderness to clearcuts). Species-specific logistic regression models based on subsets (183 and 48 points) of the original dataset corroborated the historical focus on microhabitat, but models including other scales indicated that some birds respond to coarser scale environmental characteristics. These results also supported the premise that some birds respond to multiple environmental scales. Community gradient descriptions, based on anonical correspondence analysis (CCA), supported results of logistic regression, indicating that microhabitat constituted the most important level followed by lesser, but significant, contributions from other scales. Through species-environment biplots, CCA also effectively illustrated avian habitat selection as a multiple-scale phenomenon, showing the hierarchical organization of landscape components and how they affect the spatial distribution of bird communities. FOR. SCI. 48(2):243–253.

Models for Mapping Potential Habitat at Landscape Scales: An Example Using Northern Spotted Owls - William C. McComb; Michael T. McGrath; Thomas A. Spies; David Vesely (Forest Science, 2002)
We are assessing the potential for current and alternative policies in the Oregon Coast Range to affect habitat capability for a suite of forest resources. We provide an example of a spatially explicit habitat capability model for northern spotted owls (Strix occidentalis caurina) to illustrate the approach we are taking to assess potential changes in habitat capability for vertebrates across the Coast Range. The model was based on vegetation structure at five spatial scales: the potential nest tree, a 0.5 ha potential nest patch, 28 ha around a potential nest patch, 212 ha around a potential nest patch, and a 1,810 ha home range area around a potential nest patch. Sensitivity analyses indicated that the proportion of the 28 ha patch in large trees around a potential nest patch, and the number of potential nest trees per ha in the nest patch, had the greatest influence on habitat capability estimates. The model was verified using georeferenced locations of spotted owl nests from systematically surveyed areas. Logistic regression analysis indicated that habitat capability scores were significantly associated with the probability of a site having a nest. Alternative model structures were tested during verification to test assumptions associated with four variables. The final model allowed development of a map of habitat capability for spotted owl nesting. The model will be linked to a model of forest dynamics to project changes in habitat capability under alternative land management policies. FOR. SCI. 48(2):203–216.

Regional and National Issues for Forest Wildlife Research and Management - Stephen DeStefano (Forest Science, 2002)
Biologists and managers face a broad range of issues related to research and management of forest wildlife. To assess current trends in research, I reviewed 12 scientific journals (1992–2001) that published articles on wildlife, general ecology, and forestry and summarized articles by location, topic, issue, and species. To assess management concerns and issues, I interviewed professional biologists from across the United States, asking their opinions on important forest wildlife topics, approaches to improve research design, how management differs on public versus private lands, and which species they thought were underrepresented, overrepresented, or of special concern in their region. Most scientific articles focused on habitat selection, effects of forest alteration, and demography of birds and mammals. Herpetofauna (i.e., amphibians and reptiles) and invertebrates, although the subjects of some studies, made up only 10% each of all research papers. Biologists were most concerned with the alteration of forest vegetative structure due to timber harvest and its effects on wildlife populations and communities, but also recognized other issues such as changes in natural disturbance patterns such as fire, effects of road building, and loss of early successional vegetative communities as well as fragmentation of older forests. Most biologists agreed that long-term, large-scale, experimental studies, which document the demographic response of forest wildlife to alterations in forest cover, are needed. FOR. SCI. 48(2):181–189.

The Effectiveness of Stand-Level and Landscape-Level Variables for Explaining Bird Occurrence in an Industrial Forest - John M. Hagan; Amy L. Meehan (Forest Science, 2002)
We evaluated the effectiveness of habitat variables derived at two spatial scales for explaining the presence or absence of 20 bird species at 363 point count stations in an extensive industrial forest in Maine. Sixteen stand-level (microhabitat) and seven landscape-level (within 1 km radius, or 3.14 km2) variables were used in stepwise logistic regression models to evaluate the relative roles of these two spatial scales for explaining each species' occurrence at a point count station. Species were classified as either early-successional (n = 6) or late-successional (n = 14) species for analysis. Three regressions were run for each of the 20 species: (1) stand variable only, (2) landscape variable only, and (3) stand and landscape variables combined. Regression models that included only stand-level variables averaged significantly higher model concordance scores than regression models that included only landscape variables. For 17 of 20 species, regressions that included only stand-level variables better explained the presence or absence of a species at a point than did regression that included only landscape-level variables. The presence of two species was better explained by landscape variables, and the presence of one species could not be explained by either stand- or landscape-level variables. Because many variables were positively associated with presence of some species and negatively associated with other species, management for particular stand- or landscape-level features must be preceded by a determination of which species are more important to conserve. FOR. SCI. 48(2):231–242.

Salamander Abundance in Regenerating Forest Stands on the Monongahela National Forest, West Virginia - Jeffrey P. Duguay; Petra Bohall Wood (Forest Science, 2002)
We compared the abundance of salamanders in 18 hardwood stands treated with two-age management 15 yr after harvest, clearcutting 15 yr after harvest, and mature second-growth stands in the Monongahela National Forest of West Virginia during the summers of 1995 and 1996. Salamanders were captured with pitfall traps. We sampled 47,083 trap days and captured eight species of salamanders. Abundance of salamanders, expressed as number captured per 100 trap days, was higher (P = 0.06) in the mature second-growth than two-age treatment (two-age = 0.96 ± 0.11; clearcut = 1.46 ± 0.23; mature second-growth = 2.40 ± 0.57). Abundance of redback salamanders (Plethodon cinereus) also was higher (P = 0.09) in the mature second-growth than twoage treatment (two-age = 0.76 ± 0.14; clearcut = 1.48 ± 0.34; mature second-growth = 1.84 ± 0.51). These data indicate that 15 yr after harvest, harvested stands in the Monongahela National Forest may be less favorable than mature hardwood forests for some forest salamanders. FOR. SCI. 48(2):331–335.

Temporal Patterns in Aquatic and Avian Communities Following Selective Logging in the Upper Great Lakes Region - David J. Flaspohler; Casey J FisherHuckins; Brian R. Bub; Peter J. van Dusen (Forest Science, 2002)
We surveyed populations of birds, fish, and aquatic macroinvertebrates in and along riparian systems within northern and mixed-hardwood forests that varied in time since last selection logging. Thirteen headwater stream sites from the Otter River watershed in Michigan's Upper Peninsula were included in the study. We detected a significant negative correlation between a standard index of habitat quality for coldwater streams (Great Lakes Environmental Assessment Section [GLEAS]) and time since last selective logging. Brook char (Salvelinus fontinalis Mitch.) abundance was also negatively correlated with year of forest cut as was the abundance of selected aquatic macroinvertebrate orders (Ephemeroptera, Plecoptera, and Trichoptera) that are sensitive to anthropogenic disturbance. Thus, relative to more recently logged stands, stands with older cuts had higher indices of habitat quality, more brook char, and the dominant aquatic macroinvertebrates tended to be those generally associated with higher quality coldwater streams. In contrast, bird species richness was positively related to year of last selective logging. As expected, basal area was lower and ground cover was greater in more recently logged stands. Thus, bird species richness was higher in stands with less basal area (recent cuts) than in stands with more basal area (older cuts). Percent ground cover showed a strong positive correlation with bird species richness. Twelve bird species were detected only in recently logged (since 1990) stands. The results of this multitaxa study suggest that selective logging of riparian forests is associated with changes in local animal abundance and diversity, and these effects appear to persist for approximately 30 yr postharvest. FOR. SCI. 48(2):339–349.

Bird Use of Forest Structural Classes in Grand Fir Forests of the Blue Mountains, Oregon - Rex Sallabanks; Robert A. Riggs; Lynda E. Cobb (Forest Science, 2002)
We sampled breeding birds in 83 stands in the Blue Mountains, northeastern Oregon, 1994–1996, to describe bird use of forest structural classes in grand fir (Abies grandis) forests. We classified stands, based on basal area in different tree-size categories, into six forest structural classes: (1) stand initiation (SI); (2) stem exclusion, open canopy (SEOC); (3) stem exclusion, closed canopy (SECC); (4) understory reinitiation (UR); (5) young forest, multistory (YFMS); and (6) old forest, multistory (OFMS). Most species were detected in all structural classes, but slightly more than onethird of species analyzed (13 of 38) differed in abundance among structural classes (P < 0.004). Cluster analysis, based on structural attributes measured in each stand and weighted by avian abundance, grouped birds with similar habitat associations and allowed us to identify “non-SI associates,” “SI associates,” “structural class generalists,” and “mature forest associates.” We did not identify any species that could be considered strictly “OFMS associates.” With the exception of some SI associates, such as the mountain bluebird (Sialia currucoides) and house wren (Troglodytes aedon), we found little evidence of structural class specialization by birds. In grand fir forests of the Blue Mountains, ecologists and managers should focus on understanding how specific silvicultural prescriptions influence structural attributes that are correlated with avian abundance, rather than on stand age per se. FOR. SCI. 48(2):311–321.

Influences of Hardwood Stand Area and Adjacency on Breeding Birds in an Intensively Managed Pine Landscape - J. Chris Turner; John A. Gerwin; Richard A. Lancia (Forest Science, 2002)
We compared species richness, abundance, and community composition of breeding landbirds among three areal classes of mature hardwood stands within an intensively managed pine (Pinus taeda) landscape in the Lower Coastal Plain of South Carolina. We also compared these community metrics among rotation-age pines (≈20 yr old), the pine matrix (regenerated to rotation-age pine stands comprising 50% of the landscape), and all hardwood stands regardless of area. Approximately 220 fixed-radius point counts were conducted in 1995 and 1996. Species richness (21, 23, and 25 species, respectively) within small (n = 19; 1.0–4.4 ha), medium (n = 17; 6.0–34.4 ha), and large (n = 6; 65–560 ha) hardwood islands within the pine matrix was the same, but the trend was for richness to increase with island area. Forest interior, neotropical migrants dominated all hardwood stand areas. Most species were common to all areal classes, with only a few restricted to a particular areal class. Thus, there was little evidence that these hardwood islands, embedded in a managed pine landscape context, harbored unique bird communities. Species richness (40) was greatest within the matrix of pine stands of all ages, intermediate (32) in hardwood stands, and least (27) in rotation-age pine stands. Hardwood stands supported the highest total bird densities as well as the highest densities of neotropical migrants. Pine stands hosted high densities of both resident and early successional neotropical migrants. We concluded that the presence of hardwood stands embedded within a matrix of different age classes of pine likely allowed forest-interior neotropical migrants typical of hardwood stands to “spill over” into adjacent, structurally similar pine stands and vice versa. FOR. SCI. 48(2):323–330.

The Effect of Gypsy Moth Defoliation on Cavity-Nesting Bird Communities - Christopher R. Showalter; Robert C. Whitmore (Forest Science, 2002)
Gypsy moths (Lymantria Dispar) kill trees and create snags, a resource vital to cavitynesting birds. With this in mind, population trends of 11 cavity-nesting birds and their relationship to snags in an area that was defoliated by gypsy moths were investigated from 1984 to 1999. Vegetation and bird point-count data from before a major gypsy moth outbreak (1984–1986), during (1987–1988), and after (1989–1999) enabled us to ake inferences about this forest bird community. The combined abundance of the 11 cavity-nesting species examined increased during the years immediately after the outbreak (1989–1993) followed by a decline in the last 6 yr (1994–1999). The abundance of snags also increased from 1989 to 1993 followed by a decline from 1994 to 1999. Regression analysis confirmed that cavity-nesting bird populations were highly associated with snag abundance. These data suggest the importance of snags to cavity-nesting birds and that cavity-nesters were able to take immediate advantage of a new population of snags. FOR. SCI. 48(2):273–281.

Modeling Changes in Wildlife Habitat and Timber Revenues in Response to Forest Management - John M. Marzluff; Joshua J. Millspaugh; Kevin R. Ceder; Chadwick D. Oliver; John Withey; James B. McCarter; C.L. Mason; Jeffrey Comnick (Forest Science, 2002)
Few models evaluate the effects of forest management options on wildlife habitat and incorporate temporal and spatial trends in forest growth. Moreover, existing habitat models do not explicitly consider economic trade-offs or allow for landscape level projections. To address these concerns, we linked standard wildlife habitat suitability models with habitat projections from the Landscape Management System (LMS). LMS integrates spatially explicit forest inventories with forest growth, decay, and silviculture treatment (e.g., planting, thinning, harvesting) models to compare some economic and biological impacts of forest management on wildlife habitats at spatial scales ranging from the individual forest stand to the landscape. We used LMS to quantify pileated woodpecker (Dryocopus pileatus), Cooper's hawk (Accipiter cooperi), and southern red-backed vole (Clethrionomys gapperi) habitat qualities across landscapes and to project habitat changes through time. We modeled five forest management scenarios (including no action, intensive management for timber production, moderate management and intensive management to enhance mature forest structure, and mixed management for wildlife and timber) proposed for the 566 ha Satsop Forest in western Washington. The selected wildlife species' habitats (mixture of mature conifer and deciduous forests) were maximized by simply allowing the forest to grow with no management. However, this cost an estimated $929,539/yr in lost timber revenue. Intensive thinning, replanting, and retention of large trees increased habitat for all focal species and provided $384,558/yr return from timber. Because of potential short-term reductions in habitat that occur during long-term enhancement strategies (e.g., intensive thinning) and limited ability to model understory growth dynamics, monitoring and validation of predictions would be necessary. FOR. SCI. 48(2):191–202.

Forest Wildlife-Habitat Relationships: Introduction - Stephen DeStefano; Robert G. Haight (Forest Science, 2002)

Effects of Edge Contrast on Redback Salamander Distribution in Even-Aged Northern Hardwoods - Richard M. DeGraaf; Mariko Yamasaki (Forest Science, 2002)
Terrestrial salamanders are sensitive to forest disturbance associated with even-aged management. We studied the distribution of redback salamanders (Plethodon cinereus) for 4 yr at edges between even-aged northern hardwood stands along three replicate transects in each of three edge contrast types: regeneration/mature, sapling/mature, and poletimber/mature in northern New Hampshire. We used 2 m2 coverboard clusters at the edge, and at 5, 10, 20, and 40 m into the younger and mature stands. Salamanders were surveyed 12 times per year from May to October, approximately once every 2 wk, usually within 24 hr of a rain event. Habitat variables included board station soil temperature, litter depth, organic layer depth, depth to soil mottling, herbaceous cover, down log cover, three classes of understory hardwood stem density [0.5–1m tall, 1–2 m tall and <10 cm dbh, and >2 m tall], softwood stem density, Rubus/other stem density, and overstory basal area (ba) and mean dbh. A total of 4,038 redback salamanders were detected during 432 transect counts. The mean salamander density was 0.41/m2 across regenerating stand transects, 0.47m2 across sapling transects, and 0.69 m2 across poletimber transects. We analyzed salamander distribution by edge type, replicate, year, station (distance from edge), and their interactions. There were significant differences in salamander detections among edge types, replicates, station, and years for both counts across entire younger forest/mature forest transects and across the younger forest transect sections. There were significant interactions between edge type and distance from edge. Salamander detections were greater (P < 0.001) in pole/mature edges than in sapling/mature and regeneration/mature edges in all years. Counts in sapling and regeneration stands were not different. The pattern of salamander abundance was similar across all edge types: low abundance 40 m out in the younger stand, increased abundance near or at the edge, a decrease just inside the edge, peak abundance in the mature stand (20 m inside the edge), and decline at 40 m in the mature stand. Salamander counts differed among years across all transects, tracking yearly precipitation differences. Counts also varied seasonally; early spring and late summer counts were higher (P < 0.001) than counts in early to mid-summer and fall. Salamander counts were negatively related to total understory stem density, density of hardwood stems >2 cm tall and <10 cm dbh, and percent herb cover, and positively related to soil organic layer depth (P values <0.10). A stepwise regression model included percent herbaceous ground cover, number of hardwood stems >2 m tall and <10 cm dbh, and organic soil layer depth, and explained 29% of the variation in redback salamander counts. Our findings are consistent with reported recovery times for redback salamanders after clearcut harvesting; recovery rates even along edges may take about 30 yr. Seasonal and yearly variation must be taken into account if terrestrial salamanders are used in monitoring programs. FOR. SCI. 48(2):351–363.

Use of a Landbird Monitoring Database To Explore Effects of Partial-Cut Timber Harvesting - Jock S. Young; Richard L. Hutto (Forest Science, 2002)
We used data from the USDA Forest Service Northern Region Landbird Monitoring Program to investigate the effects of partial-cut timber harvesting on bird abundances in conifer forests within the northern Rocky Mountains. We present point-count data from four separate years of the longterm monitoring database, which included between 467 and 907 points, depending on the year. Five bird species were significantly more abundant in uncut forest stands in at least one year, and 17 species were more abundant in partially cut stands in at least one year. Four and eight species from these two groups, respectively, showed the same differences in a short-term, control/treatment comparison conducted in the same region, and no species showed contradictory treatment effects when the two studies were compared. Provided that vegetation data are coupled with bird abundance data, and provided that enough points are visited to compensate for an uncontrolled design, these results suggest that data from long-term monitoring points can be useful not only as sources of information about long-term population trends, but as sources of information about habitat relationships and the effects of land use. FOR. SCI. 48(2):373–378.

Response of Forest Floor Vertebrates to Riparian Hardwood Conversion Along the Bear River, Southwest Washington - James G. MacCracken (Forest Science, 2002)
The conversion of riparian red alder (Alnus rubra) forest to conifers for salmon (Oncorhynchus spp.) habitat improvement is controversial. I monitored changes in vegetation, microclimate, and the abundance, distribution, and body condition of small mammals and amphibians during the initial stage of alder conversion. Treatments reduced alder and moss cover [mean standardized effect size (ES) = -2.38 and -1.23, respectively (P = 0.0001)], but increased shrub and forb cover [ES = 0.98 and 0.37, respectively (P = 0.0001)]. Treatment effects on microclimate were neutral to moderate (ES = 0.00 to 0.67, P = 0.2). Effects on pitfall trap capture rates of small mammals were small to moderate (ES = -0.04 to 0.51, P = 0.2) and varied by taxon, and effects on captures of amphibians were small (P = 0.2), but positive (ES = 0.05 to 0.26). Pitfall captures were influenced more by seasonal weather patterns than treatment effects on vegetation. Differences in the density of torrent salamanders (Rhyacotriton kezeri) in streams in conversion and control sites were large (ES = -1.00, P = 0.4) and moderate for giant salamanders [ Dicamptodon spp. (ES = 0.31, P = 0.4)]. Treatment effects on the mass/individual for three species of shrew were small (P = 0.2 to 0.9) and either negative or neutral (ES = -0.21 to 0.00) for juveniles and adults. Effects on the mass of western red-backed salamanders (Plethodon vehiculum) were small for adults (ES = -0.12, P = 0.6) and juveniles (ES = 0.08, P = 0.8). Treatment effect on the mass of red-legged frogs (Rana aurora) was positive ( P = 0.2) for both age classes (adult ES = 0.52, juvenile ES = 0.20). The effect of conversion on the mass of torrent salamanders was positive (adult ES = 1.00, P = 0.002; juvenile ES = 0.25, P = 0.02). Additional research should focus on confirming my results, longer term effects, and additional wildlife species. FOR. SCI. 48(2):299–308.

Habitat Requirements for the Conservation of Arboreal Marsupials in Dry Sclerophyll Forests of Southeast Queensland, Australia - Kevin Ray Wormington; David Lamb; Hamish Ian McCallum; Damien John Moloney (Forest Science, 2002)
The habitat requirements of arboreal marsupials were investigated in the dry sclerophyll forests of southeast Queensland, Australia. Species richness and abundance of arboreal marsupials was correlated to the proportion of total stand basal area occupied by lemon-scented gum (Corymbia citriodora), the height of the tallest trees, and density of hollow-bearing trees. The first two factors suggested that the most productive forests were also the most suitable habitats for arboreal marsupials. Importantly, the number of hollow-bearing trees was a significant factor in determining species richness and abundance of arboreal marsupials in this study, with the maximum number of species reached at sites containing≥4 hollow-bearing trees/ha, and maximum abundance occurring at sites with≥6 hollow-bearing trees/ha. The proportion of C. citriodora was significant for the presence of the common brushtail possum (Trichosurus vulpecula), greater glider (Petauroides volans), and the yellow-bellied glider (Petaurus australis), while understory Acacia sp. density was important for the presence of the sugar glider (Petaurus breviceps). The yellow-bellied glider was also affected by two other variables: the density of hollow-bearing trees >50 cm diameter at breast height (dbh), and the time since the last logging. Current “Codes of Practice” regulating the density of hollow-bearing trees and silvicultural practices in state-owned timber production forests appear to provide adequate protection for arboreal marsupials, but the recently introduced increase in timber extraction rates within state forests may be detrimental to the animals. Also, protective prescriptions do not apply to the privately owned and leasehold estates, which contain the majority of the dry sclerophyll forests in southeast Queensland. FOR. SCI. 48(2):217–227.

Effects of Management on the Composition and Structure of Northern Hardwood Forests in Upper Michigan - Thomas R. Crow; David S. Buckley; Elizabeth A. Nauertz; John C. Zasada (Forest Science, 2002)
To improve our understanding of how management affects the composition and structure of northern hardwood forests, we compared managed with unmanaged sugar maple (Acer saccharum Marsh.) dominated forests. Unmanaged old-growth and unmanaged second-growth forests provided baselines for comparing the effects of even-aged and uneven-aged forest management on selected aspects of biological diversity. Three replications of each condition were located on the Winegar Moraine in Michigan's Upper Peninsula. Old-growth forests were multistoried, dominated by a few, large trees with well-developed crowns extending over a subcanopy stratum 10–15 m in height and an abundance of woody vegetation (mostly sugar maple seedlings) at 2–3 m. This complex stand structure contrasts with the relatively uniform structure of unmanaged second-growth forests with a closed overstory canopy and limited understory development. Forest management, both even- and uneven-aged, created forest structures that were more complex than their unmanaged second-growth baselines, yet managed forests lacked some of the structural complexity characteristic of old-growth. Managed forests had fewer large trees (stem diameter at 1.37 m > 50 cm) and considerably less basal area in dead trees when compared with old-growth. There were fewer tree species in managed forests because commercially important tree species were favored for retention and, when present, early successional species (e.g., Populus grandidentata Michx., Populus tremuloides Michx.) were harvested. A subcanopy comprised of large shrubs and small trees characteristic of old growth was absent in managed forests, but this structural element may develop with time under management. As expected, thinning the overstory and disturbing the forest floor through tree harvesting promoted understory development in managed forests. Most of the added species, however, were common in the landscape and thus added little to overall species richness. FOR. SCI.48(1):129–145.

Sapwood Area as an Estimator of Leaf Area and Foliar Weight in Cherrybark Oak and Green Ash - James S. Meadows; John D. Hodges (Forest Science, 2002)
The relationships between foliar weight/leaf area and four stem dimensions (dbh, total stem cross-sectional area, total sapwood area, and current sapwood area at breast height) were investigated in two important bottomland tree species of the southern United States, cherrybark oak (Quercus falcata var. pagodifolia Ell.) and green ash (Fraxinus pennsylvanica Marsh.). In all models tested and for both species, total sapwood area was consistently more highly correlated with foliar weight and leaf area than were the other three measures. However, there was little difference in accuracy among simple linear, multiple, and nonlinear models that used total sapwood area to predict either foliar weight or leaf area. Accuracy was improved slightly through the addition of total height and live crown ratio to the linear model. Foliar weight of both species was best described as a function of total sapwood area and live crown ratio (r2 = 0.97, n = 16 for both species). Leaf area of cherrybark oak was best described as a function of total sapwood area, total height, and live crown ratio (r2 = 0.96, n = 16), whereas leaf area of green ash was best described as a nonlinear function of total sapwood area (r2 = 0.95, n = 16). In contrast with other studies on upland oaks in relatively cool climates, we found that current sapwood area was only a fair estimator of foliar weight and leaf area in cherrybark oak and was a poor estimator in green ash. These results lead to the speculation that more of the sapwood than just the most recent one or two growth rings may be active in water conduction in bottomland species in warm climates. Specific leaf area was highest in the lower crowns of trees of both species and was highest among trees of the lower crown classes. Although based on a limited sample size of four trees per crown class per species, we found that the vertical distribution of foliage within the crown differed among crown classes in both species. Most of the foliage on dominant and codominant trees of both species was concentrated in the upper one-third of the crown, with only a very small proportion of the foliage in the lower one-third of the crown. Intermediate and overtopped cherrybark oaks and intermediate green ash trees had a more even distribution of foliage throughout their crowns, while the foliage of overtopped green ash trees was highly concentrated in the lower one-third of the crown. The leaf area:sapwood area ratio did not differ significantly among crown classes in either species, but averaged 0.67 m2 cm-2 in cherrybark oak and 0.24 m2 cm-2 in green ash. FOR. SCI. 48(1):69–76.

The Ratio of Live Crown Length to Sapwood Area as a Measure of Crown Sparseness - Douglas A. Maguire; Alan Kanaskie (Forest Science, 2002)
Leaf area density is a biologically appealing index of forest tree health because it can provide an assessment of foliage loss or retention; however, it is difficult to measure directly. In contrast, the ratio of crown length to sapwood area (CL:SA) is quite amenable to objective field measurement, and could be interpreted as an index of crown sparseness. CL:SA was computed for Douglas-fir trees from 70 plots covering a range in average size, stand density, site quality, and crown condition in the Oregon Coast Range. When expressed as cm:cm2, the index ranged from 2 to 100 for individual trees and from 2 to 11 for plot averages based on the 200 largest trees per ha. In general, individual trees with a high CL:SA had a lower relative height within the stand. The index also increased with increasing severity of needle loss on sites where Swiss needle cast (SNC) is causing premature loss of foliage. After correcting for stand density and stand age, plot basal area growth increased significantly with a decrease in plot average CL:SA across a gradient in Swiss needle cast severity. CL:SA has strong potential for discriminating effectively among stands with varying degrees of foliage loss and growth reduction due to other disturbances as well, such as air pollution and defoliating insects. FOR. SCI. 48(1):93–100.

Co-integration of Timber and Financial Markets—Implications for Portfolio Selection - V-P. Heikkinen (Forest Science, 2002)
The short-run and long-run correlations between Finnish forestry returns and financial market instruments are examined. Financial assets include the general stock market index HEX, bond rate and deposit rate. The results indicate that timber prices and bond and deposit rates are co-integrated in the long run. The study demonstrates the influence of co-integration on expected asset returns and the optimal investment portfolio. FOR. SCI. 48(1):118–128.

Heritability of Ozone Sensitivity in Open-Pollinated Families of Black Cherry ( Prunus serotina Ehrh.) - J.C. Lee; K.C. Steiner; J.W. Zhang; J.M. Skelly (Forest Science, 2002)
First-year seedlings of black cherry, representing 10 open-pollinated families from wild parents, were exposed in CSTR chambers to replicated treatments of 30, 60, 90, and 120 ppb ambient ozone for a 7 hr day-1, 5 day wk-1. Stem height, occurrence of leaf senescence, and visible foliar injury expressed as adaxial stipple were measured weekly during the 10 wk duration of exposure. Basal stem diameters were measured before and after fumigation. Stipple began to occur in week 1 of the 120 ppb ozone treatment, week 2 of the 90 ppb treatment, and week 4 of the 60 ppb treatment. No stipple occurred on any seedlings exposed to 30 ppb ozone. Premature leaf senescence occurred in all treatments, but sooner and more severely at higher concentrations of ozone. Relative diameter growth rates declined as ozone concentrations increased. Families differed significantly in their response to ozone treatments in severity of adaxial stipple, but not in leaf senescence or height or diameter growth. Family heritability estimates for foliar injury, calculated by treatment and week of measurement, were generally above 0.5 in the 90 and 120 ppb ozone treatments. The relative ozone sensitivity of these 10 families under CSTR conditions corresponded well with sensitivity rankings of their 27-yr-old parents, replicated in a clonal seed orchard, and growing under ambient ozone exposures. The existence of localized, heritable variation in ozone sensitivity in wild populations has obvious implications for the use of bioindicators in forest health monitoring. For. Sci. 48(1):111–117.

The Effect of Positional Errors on the Accuracy of Estimates in Guided Transect Sampling - Anna Ringvall; Göran Ståhl; Tomas Lämås (Forest Science, 2002)
Guided transect sampling was recently proposed as a method for sampling sparse and geographically scattered populations if auxiliary data with high spatial resolution are available prior to the inventory. In practice, a surveyor will use GPS to follow predetermined survey lines. However, the surveyor will never be able to follow the lines exactly, and thus the accuracy of estimates is likely to be affected. The aim of this article was to study the loss in accuracy of estimates in guided transect sampling due to errors in navigation. The evaluation was made through Monte-Carlo simulations in different simulated forest types. The auxiliary data were considered to be volumes of deciduous trees, and the variable of interest the abundance of an indicator species connected to deciduous trees. To describe the surveyors' movements along the survey lines, a Brownian bridge process was proposed and evaluated with field data. The results from the study indicate that errors in navigation only have a minor effect on both bias and standard errors of estimates of the population total. The bias was not higher than 2.9%, and the increase in standard error not higher than 3.2 % in any forest type. FOR. SCI. 48(1):101–110.

Correction for Slope in Point and Transect Relascope Sampling of Downed Coarse Woody Debris - Göran Ståhl; Anna Ringvall; Jeffrey H. Gove; Mark J. Ducey (Forest Science, 2002)
In this article, the effect of sloping terrain on estimates in point and transect relascope sampling (PRS and TRS, respectively) is studied. With these inventory methods, a wide angle relascope is used either from sample points (PRS) or along survey lines (TRS). Characteristics associated with line-shaped objects on the ground are assessed, e.g., the length or volume of downed logs. In their basic forms, the methods only work in flat terrain, and thus bias is incurred under sloping conditions. Two different possibilities to correct for bias due to slope are presented. The first one involves using a slightly modified relascope device and making a measurement of the angle of inclination of each sampled object. The second involves applying correction factors based on the steepness of the terrain in the area surveyed. However, it is shown that moderate slopes cause only limited bias and in such cases there is little need to adjust the measurement procedures or apply correction factors. For. Sci. 48(1):85–92.

Growth and Nutritional Interactions of Nutrient-Loaded Black Spruce Seedlings with Neighboring Natural Vegetation Under Greenhouse Conditions - Moses Imo; Victor R. Timmer (Forest Science, 2002)
Nutrient loading during nursery culture to improve early outplanting performance of black spruce (Picea mariana [Mill.] BSP) seedlings on weed prone sites is increasingly practiced in northern Ontario, but more insight is needed on the competitive mechanisms involved. Vector competition analysis was used to examine nutrient loading on interspecific growth and nutritional interactions between planted seedlings and neighboring natural vegetation under controlled greenhouse conditions. Nutrient loaded and conventional (nonloaded) seedlings were raised in a commercial green-house and then transplanted in bioassay soil substrates retrieved from two forest sites [Hardwood (OG 10) and Feathermoss (OG 4)], with weeds removed or left to grow naturally. Weed control increased seedling growth on the Hardwood substrates (103–194% height increase), but had no effect on the Feathermoss substrates suggesting that no seedling–natural vegetation interactions occurred on the latter site. Nutrient loading, however, countered weed competition on the competition-prone Hardwood site, reflecting the high competitiveness of these seedlings. Vector competition analysis revealed that tree-vegetation interactions on the Hardwood site caused antagonistic nutrient dilution primarily due to competition for N. Nutrient interactions were more symmetric with nutrient-loaded trees, indicating that these seedlings were less sensitive to competition than were nonloaded seedlings. For. Sci. 48(1):77–84.

Designing Compact and Contiguous Reserve Networks with a Hybrid Heuristic Algorithm - Darek J. Nalle; Jeffrey L. Arthur; John Sessions (Forest Science, 2002)
Conflicting opinions from environmental advocates and economic interests on the best strategy for management of public lands often leaves land managers in a difficult position. Since ecosystem sustainability is in the long-term interest of each group, the establishment of nature reserves could simultaneously address both views. To promote sustainability, fragmentation of existing natural habitats should be avoided, since it is commonly recognized as being disruptive to the species adapted to these habitats. Therefore, when designing an efficient nature reserve, the compactness and contiguity of the land reserved is an essential consideration. A new formulation of the reserve selection problem is presented that explicitly addresses these issues; specifically, the model minimizes a weighted combination of compactness and contiguity measures subject to constraints on the minimal representation of each habitat class. Motivated by the ongoing reserve efforts in the large and diverse Klamath-Siskiyou region of southwestern Oregon and northwestern California, common heuristic search techniques are implemented and results compared on various simulated test problems. From these findings a new heuristic is developed that reduces solution time and increases solution quality. When applied to the Klamath-Siskiyou region, results are promising. FOR. SCI. 48(1):59–68.

Examining Different Concepts for the Development of a Distance-Dependent Competition Model for Red Pine Diameter Growth Using Long-Term Stand Data Differing in Initial Stand Density - G.R. Larocque (Forest Science, 2002)
Red pine (Pinus resinosa Ait.) data collected from age 13 to age 43 in a spacing trial were used to develop a distance-dependent individual-tree diameter growth model. The traditional concept of zone of influence in competition indices was redefined, and differences in asymmetry in above- and below-ground competition were represented. The availability of remeasured crown dimensions data allowed for realistic representation of the dynamics of crown interference at the canopy level. Diameter at breast height (dbh) increment was expressed in terms of absolute growth rate, relative growth rate, and ratio of absolute growth rate to crown width. The best relationships accounted for at least 80% of the variability in dbh increment. When tested on an independent data set, the model predicted dbh increment relatively accurately under different conditions of stand density. In particular, the change in dbh size distribution with the increase in competitive stress was well represented. FOR. SCI. 48 (1):24–34.

Modeling the Joint Distribution of Tree Diameters and Heights by Bivariate Generalized Beta Distribution - Fasheng Li; Lianjun Zhang; Craig J. Davis (Forest Science, 2002)
A bivariate generalized beta distribution (GBD-2) is fit to the joint frequency distribution of tree diameters and heights of 43 Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) plots in Idaho. The model fitting and performance are compared with the Johnson's SBB distribution using goodness-of-fit χ2 tests for the marginal distributions of diameters and heights, a bivariate goodness-of-fit test for the joint distribution of the two variables, and model predictions of tree heights and volumes. We found that the GBD-2 is more flexible and successful than the Johnson's SBB in describing both marginal and joint distributions of tree diameters and heights. On average, the relative bias (%) from the GBD-2 is three times smaller than that from the Johnson's SBB across the 43 plots when the models are used in tree volume prediction. FOR. SCI. 48(1):47–58.

Combining Tabu Search and Genetic Algorithm Heuristic Techniques to Solve Spatial Harvest Scheduling Problems - Kevin Boston; Pete Bettinger (Forest Science, 2002)
The performance of two new heuristics that combine tabu search with a genetic crossover technique was examined for their usefulness in solving spatially constrained harvest scheduling problems. One heuristic utilized tabu search with 1-opt moves and a genetic crossover technique (TS/GA), and the other utilized tabu search with both 1-opt and 2-opt moves and a genetic crossover technique (TS2/GA). The heuristics were tested on four problems. Three problems used the simple unit-restriction model (URM) to portray greenup constraints, allowing them to be solved with mathematical programming techniques and thus providing a benchmark to compare against the solutions produced by the heuristic techniques. These were considered hypothetical problems, since the datasets were grids, and the age classes were assigned with three different rules. The fourth problem uses an operational dataset and includes both a maximum opening size constraint, which limits the size of an individual opening, and a maximum average opening size constraint, which represents the greenup constraint contained in the American Forest and Paper Association (AF&PA) Sustainable Forestry Initiative (AF&PA 2000). The greenup constraints contained in these problems accurately portray the greenup constraints facing the forest industry in the United States. For the three hypothetical problems, the TS/GA technique found solutions with an objective function value between 96.6% and 99.1% of an estimated optimal value, and between 93.4% to 94.4% of a relaxed linear programming value. The TS2/GA found better solutions for all three hypothetical problems, with the objective function values between 98.2% and 99.7% of the estimated optimal value and the 96.3% to 97.2% of the relaxed linear programming value. Compared with a general tabu search technique that used 1-opt moves (TS), adding the genetic crossover technique resulted in a 2% increase in the objective function value, and adding the 2-opt intensification capability resulted in a further 1.5% improvement. A similar pattern was observed when the problem using the operational dataset was solved. The addition of the genetic crossover technique did not increase the time required to produce a solution to any particular problem, yet the addition of the 2-opt procedure did. TS2/GA required about twice as much time as did TS or TS/GA when applied to the three hypothetical datasets, and 67% more time when applied to the problem using the operational dataset. FOR. SCI. 48(1):35–46.

Precision of Density Estimates from Fixed-Radius Plots Compared to N -Tree Distance Sampling - V.C. Lessard; T.D. Drummer; D.D. Reed (Forest Science, 2002)
We computed and compared the statistical properties of the estimators for the number of trees/ha (density) for fixed-radius plot and n-tree distance sampling. In forests with random spatial patterns, n-tree distance sampling density estimators are at least as precise as those of plot sampling if the fixed-radius plot size is less than the ratio of (n - 2) and the expected density, where n is the number of trees included at an n-tree location. A similar result holds for the clustered forest, where the ratio is multiplied by a factor involving a constant of heterogeneity. If the expected number of trees per plot and the plot sizes are the same for both the random and clustered spatial patterns, the variance of the plot sampling density estimator for the clustered pattern will always be greater than for that of the random spatial pattern. FOR. SCI. 48(1):1–6.

African Rain Forest Ecology and Conservation: An Interdisciplinary Perspective - Timothy R. Baker (Forest Science, 2002)
Current conservation strategies focus on achieving sustainable development by viewing the protection of species and habitats within a broader economic and social context. This approach places complex demands on conservation projects, particularly within the African rain forest, with its great biological, political, and historical diversity. Originally dating from a conference organized by the Wildlife Conservation Society in 1993, this book brings together contributions that allow the examination of whether successful, integrated strategies are evident within African rain forest conservation.

The Ecology of Trees in the Tropical Rain Forest - Ronald L. Hendrick (Forest Science, 2002)
The primary literature describing the ecology of tropical rain forest trees is vast, yet there are relatively few summaries of their ecological traits, especially from a comparative ecology perspective. Consequently, Turner's effort to do a comparative analysis of the ecology of species from throughout the tropical rain forest is a most welcome one. His primary goal to summarize the ecology of different tropical rainforest trees has resulted in a very well written summarization of their comparative ecology (and structure). He is less complimentary of the results of his effort to find “a new synthesis of the comparative ecology of tropical trees” (p. 247) after summarizing the relevant literature, but perhaps he has done more than he suspects.

Comparing Fixed- and Variable-Base-Age Site Equations Having Single Versus Multiple Asymptotes - C.J. Cieszewski (Forest Science, 2002)
Site equations compute values of a variable Y as a function of both variable t and a value of the variable Y = Y0 measured at an arbitrary t = t0. For example, the plant size (Y) can be defined as a function of both age (t) and a reference size (Y0) measured at the base age t0. The base age can be implicit (i.e., implied but hidden), as in fixed-base-age equations [e.g., Y = f(t, S), where S is Y at t = 50], or explicit (i.e., readily exposed and changeable), as in dynamic equations [e.g., Y = f(t, t0, Y0)]. Using as the main criterion the ability of an equation to generate concurrent polymorphism and multiple asymptotes, I compare a fixed-base-age height growth site equation with several dynamic equations, derived through the traditional and the Generalized Algebraic Difference Approaches. The comparison leads to conclusions about desirable model properties, the methodologies of derivations, and expected outcomes of the different methodologies. The conclusions suggest that the ability to simulate concurrent polymorphism and multiple asymptotes is an important property of site equations that should be considered during modeling various growth trends. Furthermore, the conclusions suggest that both algebraic difference approaches are more parsimonious and robust than the fixed-base- age approaches. The Generalized Algebraic Difference Approach can increase model usefulness considerably through derivation of more complex equations that can achieve more desirable properties. FOR. SCI. 48(1): 7–23.

Forest Policies and Many Governments - Gregory S. Amacher (Forest Science, 2002)
In this article, I examine pressures on the forest stock when multiple governments, which control different policies, have distinct revenue needs and respond to different constituencies. I assume one type of government controls public forest harvesting, while other governments (typically local or lower ones) control taxes on productive firms in their constituency. Preservation of public forests provides nontimber benefits, or public goods, for consumers at both local and national levels, and these public goods values may vary across constituencies. I investigate how public goods depend on types of government coordination including revenue sharing, shared constituencies, transfers between governments, and federalism (i.e., where one government responds only to its own revenue needs and constituencies without regarding the impact on other governments' revenues or constituents). The results suggest there are several forms of government coordination that either enhance or reduce fiscal constraints imposed on governments, and these spill over onto the forest stock through policy-induced changes in harvesting. In contrast to previous work, in the forestry case reduced government coordination and fiscal federalism can actually protect forest resources and increase public goods produced from preserving forests. If governments perceive increased revenues from public harvesting, then forest exploitation is reduced by shifting fiscal responsibilities away from governments that own resources. It is also shown that pure transfers may not reduce pressures on forest stocks unless certain restrictive conditions are met, and revenue sharing can provide incentives to increase public harvesting and reduce public goods in order to support revenue collections of all governments. Forest Science 48(1):146–158.

Woody Plants and Woody Plant Management: Ecology, Safety, and Environmental Impact - James H. Miller (Forest Science, 2001)
Wise and effective woody plant management is an increasing necessity for many land uses and conservation practices, especially on forests and rangelands where native or exotic plants are affecting productivity, access, or critical habitat. Tools and approaches for managing woody plants have been under concerted development for the past 50 years, integrating mechanical, herbicidal, manual, cultural, and biocontrol techniques. This period was fraught with controversy as herbicide use increased with its consequences persistently questioned. Nevertheless, eager adopters of new tools and strategies have been managers for forestry, range, right-of-ways, wildlife, recreation, industrial sites, and more recently natural areas and preserves. Drawn to the generic title of this book, all these users would have great expectations for information to fit their many needs.

Foreign Direct Investment, Exports and Exchange Rates: The Case of Forest Industries - Jussi Uusivuori; Susanna Laaksonen-Craig (Forest Science, 2001)
Foreign direct investment (FDI) by forest companies has increased rapidly in the 1990s. An interesting question is to what extent FDI and traditional trade in the forest sector are substitutes or complements to each other. For example, does FDI lead to increased or decreased exports of forest products from the home country in the long run? This article explores the dynamic relationship between FDI and exports of forest industries with U.S., Finnish, and Swedish data. Both short-term and long-term interrelationships between FDI and exports are studied, as well as the short-term and long-term effects of exchange rate movements and exchange rate variation. The results show that for the U.S. forest industries, FDI and exports of forest products may have become full substitutes in the 1990s. In the case of the Finnish and Swedish forest industries, exports seem to affect negatively the investments abroad, while FDI does not affect exports in the long run. Both the FDI and exports by the U.S. forest industries are unaffected by dollar variability. In the 1980s, the strengthening value of the dollar increased the FDI by the U.S. forest industries. FOR. SCI. 47(4):577–586.

The Cambridge Illustrated Glossary of Botanical Terms - Edward C. Jensen (Forest Science, 2001)
This glossary provides definitions and illustrations of over 2400 terms used to describe and classify vascular plants. The majority of terms refer to structural parts of plants visible to the naked eye or with a low power hand lens. The book is divided into two major sections: a glossary without illustrations and a set of labeled illustrations without definitions, requiring one to flip back and forth between sections for both. The illustrations are simple but effective, and all of the terms identified in the illustrations are well defined in the glossary. I found the combination to be an effective and efficient way to accomplish the authors' goals.

Forest Certification: Roots, Issues, Challenges, and Benefits - Steven R. Radosevich (Forest Science, 2001)
Foresters have been involved in a serious debate with other members of society for at least three decades over the environmental and social consequences of continuing to manage forestlands as they have been. This debate takes many forms, ranging from simple disagreement to new laws and regulations, market boycotts, and even civil disobedience by some members of the public. Foresters and many environmental organizations alike have looked for ways to resolve these ever-present concerns about the environmental, ecological, economic, and social consequences of forest management, while providing incentives for forest landowners to change their practices. Forest certification, as a voluntary, economically driven process, may be the mechanism for resolution to eventually occur, for the debate to end.

Tropical Deforestation, Tenure Insecurity, and Unsustainability - Edward B. Barbier; Joanne C. Burgess (Forest Science, 2001)
This article explores the effects of tenure insecurity on the migrant's decision to convert tropical frontier forestland to unsustainable agriculture. We develop and extend a Faustmann model to explore the effects of insecure property rights and unsustainability on the migrant's decision to convert tropical forestland to crop production, to maintain it for long-term timber production, or to mine the forest for timber and then abandon the land. We then provide a numerical simulation of the migrant's land-use decision based on data from the Amazon to compare the returns to mahogany plantation as opposed to agricultural conversion or timber mining. Increasing insecurity of land tenure leads to a decline in the value of timber relative to agricultural production land, thus creating an incentive for forest conversion. However, when land is easily degraded and tenure insecurity is high, timber mining and land abandonment may be a particular problem. Finally, we examine the role of private and government investment in establishing and maintaining secure land tenure. Once government “arrives” at the frontier, it can encourage sustainable timber production through providing secure harvesting rights and setting an optimal concession fee. FOR. SCI. 47(4):497–509.

Optimal Private and Public Harvesting under Spatial and Temporal Interdependence - Erkki Koskela; Markku Ollikainen (Forest Science, 2001)
This article extends the Hartman model to include the case where two adjacent stands may be interdependent in the provision of amenity services. We show first that the relationship between the focal and exogenous rotation age depends on the nature of their temporal interdependence, that is, on what happens to the degree of substitutability or complementarity between the stands when the rotation age of the private focal stand changes. We then apply this analysis to the determination of public rotation age in a two-stage game where the government first decides on its harvesting, and private harvesting is chosen in the second stage. Several new rules are derived for the socially optimal design of public harvesting depending on the nature of interdependence between private and public stands as well as on whether or not citizens have access to private forests for recreation. FOR. SCI. 47(4):484–496.

Generalization of Faustmann's Formula for Stochastic Forest Growth and Prices with Markov Decision Process Models - Joseph Buongiorno (Forest Science, 2001)
Faustmann's formula gives the land value, or the forest value of land with trees, under deterministic assumptions regarding future stand growth and prices, over an infinite horizon. Markov decision process (MDP) models generalize Faustmann's approach by recognizing that future stand states and prices are known only as probabilistic distributions. The objective function is then the expected discounted value of returns, over an infinite horizon. It gives the land or the forest value in a stochastic environment. In MDP models, the laws of motion between stand-price states are Markov chains. Faustmann's formula is a special case where the probability of movement from one state to another is equal to unity. MDP models apply whether the stand state is bare land, or any state with trees, be it even- or uneven-aged. Decisions change the transition probabilities between stand states through silvicultural interventions. Decisions that maximize land or forest value depend only on the stand-price state, independently of how it was reached. Furthermore, to each stand-price state corresponds one single best decision. The solution of the MDP gives simultaneously the best decision for each state, and the forest value (land plus trees), given the stand state and following the best policy. Numerical solutions use either successive approximation, or linear programming. Examples with deterministic and stochastic cases show in particular the convergence of the MDP model to Faustmann's formula when the future is assumed known with certainty. In this deterministic environment, Faustmann's rule is independent of the distribution of stands in the forest. FOR. SCI. 47(4):466–474.

The Effects of Legal Limits and Recommendations on Timber Production: The Case of Finland - Kari Hyytiäinen; Olli Tahvonen (Forest Science, 2001)
One form of legislative regulation on private forestry does not allow a stand to be clearcut until it exceeds a certain average diameter or age. This study examines whether this type of regulation used in Finland, for example, constrains the optimal timber harvesting of various site types of Norway spruce and Scots pine cultures. Applying a Faustmann type of rotation model, well-established growth and yield data and economic time series, we find that the regulations constrain the optimal solution if the rate of interest exceeds 3% or 5% for Scots pine and Norway spruce stands, respectively. They turn out to be more binding, the lower the growth capacity of the stand. Especially for mature stands, the regulations may cause major economic losses. The regulations increase long-term sawlog production but decrease pulpwood production in comparison to the unconstrained optimum. Moreover, the regulations change the structure and reduce the level of costs, and may then reduce working opportunities in forestry. FOR. SCI. 47(4):443–454.

Recursive Preferences in Forest Management - Jukka Peltola; Keith C. Knapp (Forest Science, 2001)
Expected net present value (ENPV) is a commonly used criterion in optimal forest management; however, this only applies to risk neutrality. If the owner has other risk preferences, then a utility function should be used. Expected utility is the most common way to handle stochasticity in an atemporal framework, but is problematic in intertemporal problems.Recursive preferences overcome a variety of the difficulties associated with expected utility in stochastic control problems. Recursive preferences (RP) are applied here to forest management. The effects of risk aversion and intertemporal substitution on optimal management are weighed using this framework. Compared to ENPV, RP with empirically plausible levels of intertemporal substitution implies substantially increased harvest levels in the early years, which drastically reduces the stock growth rate. In contrast, risk aversion has little or no impact on optimal management except for an infinite elasticity of intertemporal substitution. In this instance, increasing risk aversion lowers the time to steady-state and the level of steady-state forest stocks. For. Sci. 47(4):455–465.

Combining Forest-Level Analysis with Options Valuation Approach—A New Framework for Assessing Forestry Investment - Runsheng Yin (Forest Science, 2001)
The conventional forest investment assessment at the stand level has difficulty dealing with multiple decisions and capturing the operational flexibility involved in timber production. By combining forest-level analysis with the options valuation approach, this article suggests a new framework for forestry investment assessment. We first articulate the new framework and discuss a few technical issues encountered in adopting it. Then, we present three empirical examples (entry decision, land acquisition, and harvest timing) to illustrate how forest-level analysis and/or real options valuation can be done and what we may learn from this type of exercise. We believe that while adopting this new framework entails challenges, it represents a great opportunity to expand the field of forest investment assessment. FOR. SCI. 47(4):475–483.

Introduction—The Faustmann Formula: Fundamental to Forest Economics 150 Years After Publication - Richard J. Brazee (Forest Science, 2001)

Large Landscape Scale Analysis of Tree Death in the Adirondack Park, New York - P.D. Manion; D.H. Griffin (Forest Science, 2001)
We propose that healthy forests depend on quantitatively predictable tree death as a continuous process linked to forest structure and growth. Quantifying a baseline mortality value by forest structure analysis using the Law of de Liocourt allows estimation of forest health by comparing the observed mortality to a baseline value. This method is applicable to large landscape samples, but not generally to individual forest stands. Observed relative mortality per dbh class from a random sample of the Adirondack Park (New York, USA) forest was slightly, but significantly, less than the baseline relative mortality per dbh class required for maintaining size-distribution stability of the forest. This result suggests a changing structure involving increased forest density, or future mortality increase to maintain the current structure. Differences in structure-mortality relationships among the more abundant species indicate changing composition of the forest. This reflects unhealthy conditions in some species (American beech, yellow birch, balsam fir, and red spruce) that are compensated by enhanced development of others (red maple, sugar maple, and eastern hemlock). For. Sci. 47(4):542–549.

Impacts on Economically Optimal Timber Rotations When Future Land Use Changes - W. David Klemperer; Daniel R. Farkas (Forest Science, 2001)
Based on a perpetual rotation assumption, changes in selected variables will have effects on the even-aged timber clearcut age (rotation) that maximizes net present value using the Faustmann formula. Alternatively, one can assume that landowners project a postharvest change in land use with a land value equal to or exceeding today's Faustmann value and that this future land value is independent of their assumed values for variables like annual costs, annual revenues, stumpage prices, and income taxes. In that case, the impact of changes in the foregoing variables on optimal rotations may be substantially greater, and sometimes in the opposite direction, compared to the standard Faustmann approach. Moreover, a higher estimated postharvest land value can shorten the optimal rotation. With a loblolly pine yield function, these rotation differences are demonstrated, using the standard, perpetual Faustmann formula and a rotation-end land use change adaptation with a fixed projected land value. Appendixes include mathematical verifications. The different interpretations depend on whether one considers the Faustmann land value as the land market value in a general equilibrium sense, or whether one takes the future market value of land as given and performs sensitivity analyses of alternative scenarios. Policy implications are difficult to assess without more research on landowner behavior. FOR. SCI. 47(4):520–525.

Forest Land Conversion Over Time: Implications for the Faustmann Formula - J.C. Burgess; D. Ulph (Forest Science, 2001)
The Faustmann timber production model has been used to examine the allocation of land between alternative forest land use options. This article provides a clarification and extension of this previous work. We use the basic forest land use options model to allow for the changes in forestland use over time. First, we modify Faustmann's original assumptions to allow for a one-off change in prices or an initial allocation constraint, and examine the forest land manager's decision to switch to an alternative land use at some point in the future. Second, we look at the case where prices evolve over time and it is optimal for the forest land manager to switch between land uses on an equilibrium path. This second extension provides a new application of the Faustmann timber production model. We discuss the theoretical insights and the implications for forest conversion. FOR. SCI. 47(4):510–519.

A Stochastic Production Frontier Analysis of Polish State Forests - Jacek P. Siry; David H. Newman (Forest Science, 2001)
This article presents a study of the efficiency of Polish state timber production and management polices following the transition to a more competitive market. The objective is to determine how well the Polish State Forests, which manage 80% of Poland's forestland and supply 85% of its timber, have adjusted, after 40 yr of central planning, to this change. The development and estimation of a stochastic frontier production function is used to analyze and evaluate the efficiency of timber production and the effectiveness of management policies. The empirical results provide evidence for the presence of substantial technical inefficiency, along with some scale economies in timber production. In addition, policies that have led to the creation of smaller forest districts, employment reductions, and logging equipment purchases are largely ineffective and perhaps even counterproductive. On the other hand, a strong support is provided for the continued privatization of forest operations. FOR. SCI. 47(4):526–533.

Comparison of Estimation Techniques for a Forest Inventory in which Double Sampling for Stratification Is Used - Michael S. Williams (Forest Science, 2001)
A number of different estimators can be used when forest inventory plots cover two or more distinctly different condition classes. In this article the properties of two approximate Horvitz-Thompson (HT) estimators, a ratio of means (RM), and a mean of ratios (MR) estimator are explored in the framework of double sampling for stratification. Relevant theoretical properties are given, and a simulation study is used to compare the properties of these estimators. It is concluded that the variance of the RM estimator is smaller than that of the approximate HT for the populations studied, but that of the MR estimator is larger. While ratio estimators are known to be biased for small sample sizes, an additional bias also occurs when the population of interest has an edge-effect. The RM classical variance estimator underestimated the true variance in the simulation study. The approximate HT estimators exhibited biases that were generally smaller than those of the RM and MR estimators for populations with an edge-effect. Its classical variance estimator was essentially unbiased. FOR. SCI. 47(4):563–576.

A Multivariate Simultaneous Prediction System for Stand Growth and Yield with Fixed and Random Effects - Zixing Fang; Robert L. Bailey; Barry D. Shiver (Forest Science, 2001)
Forest biometricians often deal with a simultaneously interdependent model system in which common stand characteristics such as dominant height, basal area, and total volume are included. Permanent plots with some specific design are usually the main source of data for such a model system to evaluate stand growth and yield in conjunction with different silvicultural treatments or site conditions. Two basic sources of errors are very common for such data. One is within-plot error, and the other is the variation from plot to plot. Within-plot variation is usually modeled by a reasonable variance function that accounts for within-plot heteroscedasticity and correlation. The between-plot variation can be modeled by random effects that allow parameters in the model to be varied from plot to plot. The more information available on these sources of variation, the more precise the predictions of the stand characteristics for a new observation. The interdependency among the components in the system is another key to the precision of the prediction. The observed components in the system can be used to improve the prediction of the unobserved components by accounting for the contemporaneous correlation among the components. A simultaneous system containing components of a nonlinear mixed effects dominant height growth model, a log-linear basal area model, and a log-linear total volume model is developed for slash pine (Pinus elliottii Engelm.) plantations with different silvicultural treatments. Accounting for both contemporaneous correlation and random effects, we have shown the gains in the precision of the prediction of new observations that were obtained from the recommended simultaneous model system, with detailed examples for distinct situations. It has been demonstrated that dominant height is the fundamental component in the three-component system. With contemporaneous correlation and random effects for dominant height considered, including random effects in basal area and total volume model proved to be unnecessary. Between-plot variation is the main source of error for dominant height prediction, dominant height itself dominates the precision of basal area prediction, and basal area itself is the main source of error for total volume prediction. With both random effects in dominant height and contemporaneous correlations among the three components considered, the error bound (half the 95% confidence interval divided by the predicted value) of total volume prediction decreased from 52.6% to 5.8%. For. Sci. 47(4):550–562.

Assessing the Priorities Using A'WOT Among Resource Management Strategies at the Finnish Forest and Park Service - Mauno Pesonen; Mikko Kurttila; Jyrki Kangas; Miika Kajanus; Petri Heinonen (Forest Science, 2001)
We examined a hybrid method, referred to here as the A'WOT [Analytic Hierarchy Process (AHP) in SWOT analysis], for improving the usability of SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis. A commonly used decision analysis method, the Analytic Hierarchy Process (AHP), and its eigenvalue calculation framework are integrated with SWOT analysis. The connection of AHP with SWOT yields analytically determined and quantifiable priorities for the factors included in SWOT analysis. The aim in applying the hybrid method is to improve the quantitative basis of strategic planning processes. After applying the A'WOT method, decision-makers have information at their disposal about how alternative strategies are congruent with internal and external environmental factors. In a decision–making process, this information can be utilized in concert with other produced decision–support elements. The A'WOT was used in connection with the strategic planning of natural resource management at the Finnish Forest and Park Service (FFPS). Four alternative strategies were produced during the planning process. The alternatives produced were Forestry Strategy (emphasis on sustainable economic use of forests); Recreation Strategy (emphasis on recreational use of forests and social and economic sustainability); Protection Strategy (emphasis on nature protection and ecological sustainability); and the Basic Strategy (current land allocation and forestry practice principles). Opportunities determined by the priorities of the scaling factors had the greatest weight in all the business units of the FFPS. The most important internal factors included both strengths (know–how, land, and water property ) along with a couple of weaknesses (lack of information concerning biodiversity due to insufficient planning resources, age, and development class structures of forests). FOR. SCI. 47(4):534–541.

BOOK REVIEWS: Writing and Presenting Scientific Papers - Sarah F. Covert (Forest Science, 2001)
Effective writing and oral presentation skills are essential tools for any scientist. Nothing less than one's employment, grant support, publication record, and scientific impact all depend on these abilities. It is surprisingly rare, however, for graduate training programs to address these issues through formal study. As a consequence, I suspect that many young scientists enter the world of independent research with less than stellar writing skills, and I know from unfortunate experience that many seasoned scholars have yet to fully master the art of the scientific seminar. There is a clear need for instruction in these areas, but how can graduate trainers effectively teach their students these skills when they most likely acquired them only through the horrors of trial and error, or the luck of natural talent? Furthermore, how can an established scientist or a motivated student polish his or her communication skills through independent study? Malmfors, Garnsworthy, and Grossman provide lucid and concise answers to these questions in their very useful, no-nonsense handbook.

BOOK REVIEWS: Invasive Plants of California's Wildlands - David Pimentel (Forest Science, 2001)
Invasive Plants of California's Wildlands provides detailed information on the biology and control of 78 nonnative plant species that were listed as Exotic Invasive Plants of Greatest Ecological Concern by the California Exotic Pest Plant Council. These invasive, nonnative species were discussed because they are already growing wild in California and are causing or have the potential to be a serious threat to state parks, preserves, and other wildlands.

Forest Productivity, Leaf Area, and Terrain in Southern Appalachian Deciduous Forests - Paul V. Bolstad; James M. Vose; Steven G. McNulty (Forest Science, 2001)
Leaf area index (LAI) is an important structural characteristic of forest ecosystems which has been shown to be strongly related to forest mass and energy cycles and forest productivity. LAI is more easily measured than forest productivity, and so a strong relationship between LAI and productivity would be a valuable tool in forest management. While a linear relationship has been observed between LAI and forest productivity, most of these data have been collected in needle-leaved evergreen stands. The generality and consistency of the relationship between LAI and productivity has not been as well established for deciduous forests. Leaf area index (LAI) and aboveground net primary production (ANPP) were measured on 16 forest stands in the southern Appalachian Mountains. These stands span a range of elevation, slope position, temperature, and moisture regimes. LAI averaged 5.8 m2 m-2 and ranged from 2.7 to 8.2. ANPP averaged 9.2 Mg ha-1 yr-1 and ranged from 5.2 to ll.8 Mg ha-1 yr-1. LAI and ANPP decreased significantly from cove to ridge sites, and ANPP decreases significantly from low to high elevation (P < 0.05, linear regression slope). Elevation-related differences in ANPP do not appear to be due to changes in precipitation, leaf nitrogen content, or site N mineralization rates. Linear ANPP-LAI equations fit to the data measured in this study were significant (P < 0.05). These relationships were not significantly different (P > 0.1) from linear relationships based on data reported in most other studies of ANPP and LAI in eastern deciduous forests of North America. However, the slope of a linear regression model based on North American eastern deciduous forests was significantly different (P < 0.05) from one based on data collected in temperate deciduous forests for the rest of the globe. The differences were slight over the range of observed data, however, and the difference may be due to a narrower range of data for North American deciduous forests. For. Sci. 47(3):419–427.

Phosphorus and Potassium Uptake Kinetics in Red Maple Seedlings - J.M. Kelly; J.K. Kelly (Forest Science, 2001)
Acquisition of nutrients by tree roots generally is viewed as a complex process. Models that make use of Michaelis-Menten kinetics concepts provide a means to mechanistically simulate nutrient uptake. The objectives of this study were to provide: (1) estimates of the Michaelis-Menten parameters Imax, Km, and Cmin for P and K uptake by red maple (Acer rubrum L.) seedlings, and (2) to test the efficacy of these values in the modeling context by using the Barber-Cushman nutrient uptake model as a test vehicle. A nutrient depletion approach that used intact seedlings and transient conditions was used to define the kinetics values. These estimates were combined with literature values to provide a full parameter set for the model. Uptake of P proceeded rapidly and yielded an average Imax of 5.5E-6 μmol cm-2 s-1. Mean Km and Cmin values for P were 15.0 and 0.001 μmol mL-1, respectively. Potassium uptake was slower with a mean Imax of 3.8E-6 μmol cm-2 s-1, and the Km and Cmin values were 10.5 and 0.003 μmol mL-1, respectively. Simulated P uptake compared poorly with observed uptake (0.8 vs. 830 μmols). However, additional model runs indicated that the lack of agreement was more the result of a low estimate of soil solution P concentration than a problem with the P kinetics values. Simulated K uptake was in much better agreement with the observed value (891 vs. 1890 μmols). The Cmin values for P and K reflect an ability to continue root uptake at extremely low solution concentrations. This may contribute to the “supergeneralist” status accorded red maple. This study indicates these Imax, Km, and Cmin values can be used in the Barber-Cushman model to simulate P and K uptake by red maple. However, use of these Imax, Km, and Cmin values needs to be tempered with the understanding that several interacting factors influence uptake. This caveat is important when generic literature values provide some or all of the numbers used to initialize the model. FOR. SCI. 47(3):397–402.

Burning Characteristics of Needles from Eight Pine Species - Richard W. Fonda (Forest Science, 2001)
Ponderosa pine (Pinus ponderosa), Jeffrey pine (P. jeffreyi), longleaf pine (P. palustris), and south Florida slash pine (P. elliottii var. densa) are fire resisters. Trees of these species are able to survive the direct effects of wildfires. Monterey pine (P. radiata), knobcone pine (P. attenuata), sand pine (P. clausa), and jack pine (P. banksiana) are fire evaders. Trees of these species are killed by wildfire, but species survive on the postfire site via seed germination. Needles were burned in a 2×2 factorial experiment to compare these eight species, all of which are prominent in fire-related communities. The experiment tested two factors—fire adaptive strategy (resisters vs. evaders), geographic region (western vs. eastern United States)—and interactions between those two factors. Flame height, flame time, ember time, burn time, percent fuel combusted, and mean rate of weight loss were measured. Longleaf pine, ponderosa pine, and south Florida slash pine had the highest values for flame height, percent fuel combusted, and mean rate of weight loss. Knobcone pine and Monterey pine had the longest ember time and burn time. Sand pine and jack pine had the longest flame time. Resisters tested highest in flame height, percent fuel combusted, and mean rate of weight loss. Evaders had greater flame and burn times. Western pines were significantly greater than eastern pines in all burning characteristics except flame time and mean rate of weight loss. Significant interactions between fire adaptive strategy and geographic region existed for all burning characteristics except mean rate of weight loss. The interaction was accounted for primarily by differences between western evaders, which had some of the highest values for each characteristic, and eastern evaders, which had some of the lowest values. FOR. SCI. 47(2):390–396.

Modeling the United States Housing Sector - Claire A. Montgomery (Forest Science, 2001)
New residential construction and improvement of existing housing account for most of the solid wood products consumption in the United States. It is important for forest policy analysts and those interested in wood products markets to understand the implications of changes in macroeconomic variables on housing markets and, hence, on wood products markets and forests. In past studies of U.S. housing markets used for long-run forest policy analysis, the time series properties of the macroeconomic data used to estimate the models were ignored. To the extent that estimation results are sensitive to those properties, the resulting model forecasts may be misleading. This study reports a structural model of the housing sector in the United States estimated using five alternative specifications to account for the time series properties of the data. Estimation results were compared, and model forecast performance was evaluated. Several stable estimation results emerged. However, further investigation is indicated for some potentially important relationships that were sensitive to model specification. FOR. SCI. 47(3):371–389.

Using the Branch and Bound Algorithm to Solve Forest Planning Problems with Adjacency Constraints - Marc E. McDill; Janis Braze (Forest Science, 2001)
This article describes an assessment of the branch and bound algorithm (BBA) for solving forest management planning problems with adjacency constraints. Four questions are addressed: (1) What are the current limits of off-the-shelf optimization software implementing the BBA in terms of types and sizes of problems that can be solved within a reasonable time? (2) To what degree can larger problems be solved if the solution tolerance gap is increased from the default 0.01%? (3) How much can solution times be reduced by increasing the tolerance gap? and (4) If the algorithm is stopped at a larger tolerance gap, how large is the true gap likely to be? To address these questions, 2,676 hypothetical, spatially explicit forest management problems with three planning periods and between 50 and 2,500 management units were created and then solved with CPLEX® Version 6.5 to tolerance gaps of 0.01%, 0.1%, 1%, or 2%. For forests with immature or regulated age–class distributions, the predicted average solution time to a tolerance gap of 0.01% was 7.6 and 17.4 min, respectively, for problems with 2,500 management units—the largest problems solved in this study. For overmature and old-growth forest problems, predicted average solution times to a 0.01% tolerance gap reached 4 hr at about 640 and 213 management units, respectively. Increasing the tolerance gap to 1% increased these limits to 1,420 and 235 units, respectively. Increasing the tolerance gap to 1% reduced solution times by at least 90% in 49% of the overmature forest cases and in 53% of the old-growth forest cases. In overmature and old-growth forest problems, the true gap averaged 0.28% and 0.41%, respectively, when the reported gap was 1%. For. Sci. 47(3):403–418.

Estimating Contingent Values for Protection from Wildland Fire Using a Two-Stage Decision Framework - Gregory J. Winter; Jeremy S. Fried (Forest Science, 2001)
The ongoing expansion of human populations into wildland areas dominated by flammable vegetation, and the concomitant increased frequency of uncontrolled wildfires that result in losses of property and human lives, has raised new questions about the optimal level of fire protection. The morphing of the problem conception from minimizing costs plus losses of natural resources to responding to the concerns of people whose homes are at risk has stimulated fire protection planners to account for potential changes in people's well-being beyond what is reflected by insured value. Knowing the perceived value of an increase in collective (agency-provided) fire protection that achieves a risk reduction target can contribute much to policy debates on the restructuring and funding of fire protection infrastructure and fuel management. To evaluate the utility of contingent valuation for assessing such risk reduction value, the value of collective fire protection at the wildland-urban interface was assessed for residents of a Michigan jack pine forest. Seventy-five percent of the 265 residents interviewed chose to participate in a hypothetical market for a 50% reduction in risk and, on average, were willing to pay over $57 a year for such risk reduction. Results were consistent with a two-stage decision model: (1) participation in the hypothetical market for risk reduction, and (2) how much the risk reduction is worth. Homeowner risk perception and objectively assessed risk both influenced the probability of market participation. For market participants, willingness to pay was related to property value and household income, suggesting that value at risk and ability to pay weigh heavily in this decision. FOR. SCI. 47(3):349–360.

Herbivory and Fire Influence White Oak (Quercus alba L.) Seedling Vigor - A.S. Adams; L.K. Rieske (Forest Science, 2001)
We manipulated arthropod and mammalian herbivory levels on white oak seedlings using a combination of insecticide applications and fencing and employed a split-split-plot design to assess the impact of single- and multiple-year burns on seedling growth over a 2 yr period. Herbivory levels increased over time on all sites, but there was no significant difference in herbivore pressure on seedlings in single-year burned, multiple-year burned, and nonburned plots. Insecticide-treated seedlings suffered less herbivore pressure than did noninsecticide treated seedlings, and mammalian herbivory was significantly reduced by the presence of a fence. Seedling height growth, shoot elongation, diameter growth, and specific leaf mass were greatest on once-burned sites, intermediate on twice-burned sites, and least on nonburned sites. Bud expansion was the only seedling performance parameter unaffected by burn treatment. Arthropod feeding was the greater component of overall herbivory, but this herbivory did not impede seedling growth. Seedling height growth and shoot elongation were more closely linked to mammalian herbivory. These results suggest that the observed herbivory may play a negligible role, and prescribed fire may be a beneficial component of a management program designed to enhance oak regeneration. FOR. SCI. 47(3):331–337.

Imputation and Model-Based Updating Techniques for Annual Forest Inventories - Ronald E. McRoberts (Forest Science, 2001)
The USDA Forest Service is developing an annual inventory system to establish the capability of producing annual estimates of timber volume and related variables. The inventory system features measurement of an annual sample of field plots with options for updating data for plots measured in previous years. One imputation and two model-based updating techniques are described and evaluated with respect to the bias and precision of their annual estimates of basal area per unit area. The evaluations indicate that simple plot-level imputation and model-based updating techniques produce adequately unbiased and precise estimates of annual mean basal area per unit area for large areas. FOR. SCI. 47(3):322–330.

Modeling and Prediction of Forest Growth Variables Based on Multilevel Nonlinear Mixed Models - Daniel B. Hall; Robert L. Bailey (Forest Science, 2001)
In this article, we describe estimation and prediction methods for nonlinear modeling of forest growth variables that are subject to nested sources of variability. The multilevel nonlinear mixed-effects models that we consider are useful for a variety of forestry applications, but we concentrate on the problem of estimating, and making projections from, growth curves for tree height based on longitudinal data grouped by location. Wolfinger and Lin consider estimating equation approaches to fitting more general nonlinear mixed-effects models, and we adapt their zero-expansion estimating equations to the multilevel case. We develop methods of prediction based on these models that allow predictions of future height both for individual trees and for plot averages. We illustrate these methods by fitting and making predictions from a Chapman-Richards type growth model for tree height data from a loblolly pine spacing study in Putnam County, Georgia. The mean and variance of prediction errors based on our methods are examined by means of cross-validation. We provide a more complete and unified presentation of linearization-based estimation and prediction based on multilevel nonlinear mixed-effects models than has previously appeared in the forestry literature, and we argue that these models lead to substantial advantages in growth and yield prediction over traditional forestry methods. FOR. SCI. 47(3):311–321.

Diameter Growth Models Using Minnesota Forest Inventory and Analysis Data - Veronica C. Lessard; Ronald E. McRoberts; Margaret R. Holdaway (Forest Science, 2001)
The Forest Inventory and Analysis (FIA) program of the USDA Forest Service North Central Research Station (NCRS) has begun replacing the 12- to 13-yr periodic inventory cycles for the states in the North Central region with annual inventories featuring measurement of approximately 20% of all plots in each of the 11 states each year. State reports on summaries of the forest resources will be produced every 5 yr. As a method of updating information on plots not visited in the current year, NCRS is developing nonlinear, individual-tree, distance-independent annual diameter growth models for species groups. The models, formulated as the product of an average diameter growth component and a modifier component, were calibrated on Minnesota FIA data from stands that were generally undisturbed, of mixed ages and of mixed species. The dependent variable is annual diameter growth. The independent variables include crown ratio, crown class, stand basal area, stand basal area larger than the subject tree, physiographic class, and latitude and longitude of plot locations. The model predictions at both the individual-tree level and plot level have negligible bias, and the models may be easily recalibrated to include new data sets obtained from the annual inventories. For. Sci. 47(30):301–310.

The Self-Thinning Surface - Huiquan Bi (Forest Science, 2001)
This article introduces a generalized expression of the self-thinning rule, B = KSα Nβ, where B is stand biomass per unit area, N is stand density, S is relative site index, and K, α and β are parameters. On log scales, this equation becomes a self-thinning surface that defines a density-dependent upper frontier of stand biomass over a gradient of site productivity for a given species. This equation is formulated for parameter estimation as a stochastic frontier function with two error components that have different distributional properties. As an example, maximum likelihood estimates of the self-thinning surface and its confidence envelope were shown for Pinus radiata (D. Don). Furthermore, site occupancy was estimated through one of the error components of the stochastic frontier function. The conditional response of mortality at any given site occupancy was revealed by using regression quantiles. Light mortality was associated with increases in site occupancy, while heavy mortality caused a reduction in site occupancy. Changes in the estimated site occupancy had a linear relationship with changes in log stand density. The dynamic interplay between site occupancy and mortality, together with the random external effects on the self-thinning frontier, was suggested to drive the growth trajectories of individual stands during stand growth and self-thinning. Consequently, individual stands seldom travel along their self-thinning frontiers but are more likely to converge toward them during the self-thinning phase of stand development. FOR. SCI. 47(3):361–370.

Benefits of Forest-Owner Collaboration and Imperfect Capital Markets - Jussi Uusivuori; Jari Kuuluvainen (Forest Science, 2001)
This article examines the effects of capital market imperfections on the optimal harvest of nonindustrial private forest owners and the potential of collaborative stand management and timber selling to counteract these effects. Monetary benefits of two-owner collaboration are derived under a binding borrowing constraint, and when borrowing and lending rates of interest differ. It is shown that collaboration offers a way to reduce the welfare loss of capital-market imperfections by permitting landowners to restore, at least partially, the separability of consumption and timber production decisions. Pooling stands enables landowners to take better advantage of the value growth of timber and to increase the profitability of their forest holdings. FOR. SCI. 47(3):428–436.

Nonlinear Mixed Effects Modeling for Slash Pine Dominant Height Growth Following Intensive Silvicultural Treatments - Zixing Fang; Robert L. Bailey (Forest Science, 2001)
A modified Richard's growth model with nonlinear mixed effects is developed for modeling slash pine (Pinus elliottii Engelm.) dominant height growth in conjunction with different silvicultural treatments. All three parameters in the model turn out to have both fixed and random individual plot or silvicultural treatments effects. Moving average correlation with 2° was identified as within-plot error structure. The advantages of the mixed effects model in prediction for new responses are demonstrated in detail by formulations and examples. The modified Richards model has a form that combines dominant height growth and site index into one model form, so the incompatibility between height growth and site index model can be avoided. The general methodologies of nonlinear mixed effects model building, such as which parameters in the model should be considered to be random and which should be purely fixed, how to determine appropriate within-plot variance covariance structure, and how to specify between-plot variation via appropriate covariate modeling, are addressed in detail. Likelihood ratio test and Akaike information criterion (AIC) are used in model performance evaluation. Some useful graphical model diagnosis tools are also presented. FOR. SCI. 47(3):287–300.

Effects of Gypsy Moth on Radial Growth of Deciduous Trees - Robin Naidoo; Martin J. Lechowicz (Forest Science, 2001)
We investigated the effect of gypsy moth (Lymantria dispar L.) larval abundance on annual radial growth of preferred, intermediate, and avoided host trees: northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), and white ash (Fraxinus americana L.), respectively. Individual trees were surveyed for gypsy moth larvae from 1979 to 1992 in a chronically infested forest on a drought-prone site in southwestern Québec. Increment cores were collected from 156 oaks, 39 maples, and 39 ash, and annual radial growth indices from 1950 to 1992 were calculated for each species. Growth was corrected for the influence of climate using regression models. For red oak, the average number of gypsy moth larvae per tree explained 73% of the variance in growth not explained by climate. Sugar maple and white ash growth was not correlated with gypsy moth larval numbers. These results are consistent with gypsy moth host preferences and provide evidence that nonepidemic levels of gypsy moth larvae can have a significant negative effect on the radial growth of individual trees. For. Sci. 47(3):338–348.

INTRODUCTION: Inventory Updates and Related Topics—From Imputations to Mixed Models - C.J. Cieszewski (Forest Science, 2001)

Clarification of the Mirage Method for Boundary Correction, with Possible Bias in Plot and Point Sampling - Mark J. Ducey; Jeffrey H. Gove; Göran Ståhl; Anna Ringvall (Forest Science, 2001)
While the mirage method of boundary overlap correction has been shown to be unbiased, an emphasis on the case of circular inclusion zones has led to an ambiguity in its presentation in much of the literature. We present a clarification of the method and show that its incorrect application leads to bias. We further show that depending on the method of slope correction, the potential for bias extends to variable radius plot sampling. Correct application of the mirage method has implications for when plots should be reflected, and how borderline trees should be handled on the reflected plots. FOR. SCI. 47(2):242–245.

Human Demographic Trends and Landscape Level Forest Management in the Northwest Wisconsin Pine Barrens - Volker C. Radeloff; Roger B. Hammer; Paul R. Voss; Alice E. Hagen; Donald R. Field; David J. Mladenoff (Forest Science, 2001)
The effects of landscape pattern on forest ecosystems have been a recent focus in forest science. Forest managers are increasingly considering landscape level processes in their management. Natural disturbance patterns provide one baseline for such management. What has been largely ignored is the pattern of human habitation patterns (i.e., housing), on landscapes. The objective of this study is to discuss landscape level management options for the northwest Wisconsin Pine Barrens based on both landscape ecology and the human demographics of the region. Using the 1990 U. S. Decennial Census we examined current housing density, seasonal housing unit concentration, historic housing density change and projected future housing densities. These data were related to land cover and land ownership data using a GIS. Housing density increase was particularly pronounced in the central Pine Barrens, an area where seasonal housing units are common. Lakes and streams were more abundant in areas that exhibited highest growth. Within national forest lands, 80% of the area contained no housing units. In contrast, only 12% of the area in small private land ownership contained no housing. These results are integrated with previous studies of presettlement vegetation and landscape change to discuss landscape level management suggestions for the Pine Barrens. For. Sci. 47(2):229–241.

Effects of Light Regimes on the Growth of Cherrybark Oak Seedlings - Yanfei Guo; Michael G. Shelton; Brian R. Lockhart (Forest Science, 2001)
Light regimes vary significantly within small forest openings, ranging from full sunlight to total shade, and they may affect the establishment and early growth of oak seedlings. We designed modified shadehouses to simulate the complex light conditions within forest openings and tested the effects of daily photosynthetically active radiation (PAR), time of direct light exposure, and the ratio of direct light to day length (direct-sunlight ratio) on height, diameter, and periodic growth of cherrybark oak (Quercus pagoda Raf.) seedlings through 2 yr. Five treatments representing the time of exposure to direct sunlight were created: NO, NOON, MORNING, AFTERNOON, and FULL. Treatments significantly affected both the height and root-collar diameter of seedlings, especially during the second growing season. The direct-sunlight ratio was linearly related to periodic height growth for the NOON treatment but not related to height growth for the other treatments. However, periodic height growth in the AFTERNOON and FULL treatments was highly correlated to mean daily PAR. Maximum periodic height growth occurred at moderate daily PAR levels. This research showed that light conditions for maximum growth of cherrybark oak seedlings change through time, with adequate shading being most favorable during the early stages of establishment. FOR. SCI. 47(2):270–277.

Relationships Between National Forest System Employee Diversity and Beliefs Regarding External Interest Groups - Kathleen E. Halvorsen (Forest Science, 2001)
This article examines the relationship between USDA Forest Service National Forest System (NFS) employee beliefs about external interest groups and the employees' race, gender, and career path. These interest groups include environmentalists, citizen activists, the timber and mining industries, range users, tribal representatives, and recreationists. Gender, race, and career path are demonstrated to be significant factors related to NFS employee beliefs about a number of these interest groups. These results suggest that NFS employee diversification policies may have introduced into the workforce a set of employees who are less positive in their expectations of the timber industry, but more positive about environmentalists and some other key interest groups. This shift is predicted to aid the NFS in working more successfully with a wider diversity of external constituencies than in the past. For. Sci. 47(2):258–269.

Influence of Two Plant Growth-Promoting Rhizobacteria on Loblolly Pine Root Respiration and IAA Activity - J.D. Vonderwell; S.A. Enebak; L.J. Samuelson (Forest Science, 2001)
A clearer understanding of factors contributing to inconsistency in seedling root growth promotion among nurseries has become important to managers as the commercial use of rhizobacteria in forest nurseries increases. To address why some bacterial strains increase root growth response while others do not, two separate experiments were conducted with loblolly pine (Pinus taeda L.) seedlings. Experiment one examined growth media. Seed were sown in either a hand-mixed peat:vermiculite:perlite (2:1:1, v:v:v) potting medum or a commercial medum—Promix® (1:1 peat:vermiculite). Seed were inoculated at sowing with an equal amount of either Bacillus subtilis strain LS211, B. subtilis strain INR7, or sterile distilled water. Seedling biomass, root length, root surface area, average root diameter, and root volume were measured at 6 and 12 wk after sowing. Growth promotion was variable and dependent on media and weeks since sowing. In a second experiment, root respiration rate and total root indole-acetic acid (IAA) content were quantified at 6 and 12 wk for seedlings grown in Promix®. In experiment two, strain INR7 decreased whole root system respiration by 22% and increased root biomass and root length compared to controls at 6 wk. Bacterial strain LS211 had no effect on root respiration. Furthermore, bacterial strain INR7 produced 1.7 times the total root IAA concentration of controls at 6 wk, whereas LS211 had no effect. Although cause and effect could not be tested, these studies suggest that root growth promotion is influenced by growth media and that IAA concentrations and root respiration rates are two physiological mechanisms correlated with rhizobacterial activity and growth promotion. FOR. SCI. 47(2):197–202.

Design of Regular Landscape Fuel Treatment Patterns for Modifying Fire Growth and Behavior - Mark A. Finney (Forest Science, 2001)
Patterns of disconnected fuel treatment patches that overlap in the heading fire spread direction are theoretically effective in changing forward fire spread rate. The analysis presented here sought to find the unit shape and pattern for a given level of treatment that has the maximum effect on forward spread rate. This occurs when the treatment units cause the fire to spread through them at the same rate as it spreads around them. Simulations suggested that these treatment patterns reduce the spread rate or fireline intensity over much of the area burned, even outside the treatment units where the fire was forced to flank. The ideal patterns are theoretically scale independent, allowing for flexible application across heterogeneous landscapes. The topology of these patterns has implications for designing landscape-level fuel treatment patterns and for understanding spatial dynamics of fuel patterns across landscapes. FOR. SCI. 47(2):219–228.

Severe Drought Effects on Mediterranean Woody Flora in Spain - Josep Peñuelas; Francisco Lloret; Ramón Montoya (Forest Science, 2001)
The severe drought in 1994 damaged the woody flora of central and southern Spain (80% of the 190 studied sites presented drought-damaged species). In 1996, after a wet year, 67% of the sites were still affected. Different degrees of damage and recovery were found among different functional types (trees or shrubs), and genera of different evolutionary history (Mediterranean or pre-Mediterranean). The Mediterranean genera, mostly shrubs evolved under Mediterranean climate conditions, i.e., later than 3.2 M years ago in the Pliocene, were more damaged by the drought than the earlier evolved pre-Mediterranean genera, mostly trees. However, the Mediterranean genera were more resilient and recovered much better after the following wet year. FOR. SCI. 47(2):214–218.

Uncertainty, Debt, and Forest Harvesting: Faustmann Revisited - Mark Fina; Gregory S. Amacher; Jay Sullivan (Forest Science, 2001)
Debt is a common feature of forestland ownership, yet it has not been formalized in previous work on uncertainty and forestry decision-making. We extend Faustmann-based price search models by introducing a debt obligation that landowners feel pressure to pay off in finite time. We assume a price arrival process that is more general than in previous search models and allows for multiple unknown offers each period. The motivation for paying off debt could be the high costs of searching for another price offer, costs of renegotiating or refinancing debt, increasing interest charges, or landowner preferences for eliminating debt. The decision problem and associated reservation price strategy depend on a comparison of costs and benefits of waiting to harvest. The timing of debt-payoff date is the critical feature of our model. We show that a debt-payoff date implies a certain path of reservation prices over time and ultimately affects harvesting behavior. The direction and magnitude of effect depends on forest maturity. We also investigate how the reservation price–debt payoff date relationship depends on debt in future rotations, nontimber income, amenity benefits, and single versus infinite rotations. Although these ideas, particularly the inclusion of amenities and nontimber income, are absent from the conventional price search literature, we show they have important effects on the optimal reservation price strategy when landowners feel pressure to pay off debts in finite time. FOR. SCI. 47(2):188–196.

Optimal Forest Conservation: Competitiveness Versus Green Image Effects - Erkki Koskela; Markku Ollikainen (Forest Science, 2001)
This article provides a theoretical framework to study the behavioral and welfare effects of forest conservation, which leads to a binding harvesting constraint for landowners. The economy is modeled as a three-stage game by the interaction of the government's conservation policy, with consequent adjustments in the domestic timber market, and in output determination in a Cournot rivalry with the foreign forest industry. More specifically, we study how the forest industry's competitiveness constrains forest conservation and whether the “green image” demand resulting from forest conservation compensates the loss in competitiveness. It is shown that although the green image effect may locally be strong enough to even increase the profits of the domestic forest industry, at the socially optimal forest conservation level it never dominates the competitiveness effect. Hence, there is a trade-off between forest conservation and competitiveness. These findings are robust to the issue of whether timber markets are perfectly or imperfectly competitive. FOR. SCI. 47(2):178–187.

Forest Resources, Government Policy, and Investment Location Decisions of the Forest Products Industry in the Southern United States - Changyou Sun; Daowei Zhang (Forest Science, 2001)
In this article, the results of an initial attempt to estimate the effects of state attributes on plant location and investment expenditure were presented for the forest products industry in the southern United States. A conditional logit model was used to analyze new plant births, and a time-series cross-section model to assess the total capital expenditure. Significant positive effects were found for personal income and forest inventory, and negative effects were found for population density. In the short run, tax and energy costs had negative impacts on new plant births in a state, while in the long run, stumpage price and environmental stringency had negative effects on the capital expenditure. Sensitivity of model specification was documented, and policy implications were discussed. For. Sci. 47(2):169–177.

Designing an Evolution Program for Solving Integer Forest Management Scheduling Models: An Application in Portugal - André O. Falcão; José G. Borges (Forest Science, 2001)
In this article, basic concepts of both genetic algorithms and evolution program design are presented. An evolution program is presented to solve a Model I harvest scheduling problem with 0-1 decision variables for the management alternatives for each stand, with annual constraints on harvested volume. An appropriate data structure (i.e., chromosome representation) is presented, as well as modified selection, crossover, and mutation strategies specially designed for application to large forest scheduling problems. Emphasis is on designing an efficient evolution program to address the complexity of large integer problem model solving and to provide both strategic and operational guidance to forest managers. A new stopping criterion for this iterative heuristic based on the asymptotic behavior of the evolution process is further presented. The new evolution program is applied to a two-product timber harvest scheduling problem in Portugal with a temporal horizon extending to seventy 1 yr periods. Results from 50 test computer runs are discussed for application to this large problem encompassing approximately 122,000 binary integer variables and 1,000 constraints. Statistic analysis of the convergence process suggests that the evolution program may seek optimal solutions at reasonable computational cost. Results thus suggest that evolutionary techniques may be used to confront the complexity of integer forest management scheduling model solving. FOR. SCI. 47(2):158–168.

Species-Independent Height-Age Models for British Columbia - Gordon D. Nigh (Forest Science, 2001)
Species-specific height-age models abound in the scientific literature. Some researchers have used Zeide's two-point system to reduce the number of models in service. However, this system requires two height-age pairs which are not always available. The purpose of this research is to develop a height-age model for British Columbia, Canada, that is independent of species. From a large database of stem analysis data, 15 plots from three coastal and seven interior species were chosen to uniformly cover the range of site index for each species. After converting the stem analysis data into height-age data, a model based on the logistic function was fit to each plot. A preliminary analysis showed that site index, geographic region (coast, interior), and shade tolerance (tolerant, intolerant) are potentially good predictors of height. These variables, along with breast height age, were incorporated into a species-independent height-age model based on the log-logistic function. An additional ten plots per species were chosen to test the model. The testing showed that the species-independent model had approximately the same accuracy as the species-specific models. Future endeavors can be directed at improving the model by incorporating more species into the analysis and including other important climatic and ecological variables. FOR. SCI. 47(2):150–157.

Analysis of Longitudinal Data from Progeny Tests: Some Multivariate Approaches - Luis A. Apiolaza; Dorian J. Garrick (Forest Science, 2001)
Longitudinal data arise when trees are repeatedly assessed over time. The degree of genetic control of tree performance typically changes over time, creating relationships between breeding values at different ages. Longitudinal data allow modeling the changes of heritability and genetic correlation with age. This article presents a tree model (i.e., a model that explicitly includes a term for additive genetic effects of individual trees) for the analysis of longitudinal data from a multivariate perspective. The additive genetic covariance matrix for several ages can be expressed in terms of a correlation matrix pre- and post-multiplied by a diagonal matrix of standard deviations. Several models to represent this correlation matrix (unstructured, banded correlations, autoregressive, full-fit and reduced-fit random regression, repeatability, and uncorrelated) are presented, and the relationships among them explained. Kirkpatrick's alternative approach for the analysis of longitudinal data using covariance functions is described, and its similarities with the other models discussed in this article are detailed. The use of Akaike's information criterion for model selection considering likelihood and number of parameters is detailed. All models are illustrated through the analysis of weighed basic wood density (in kg/m3) at four ages (5,10,15, and 20 yr) from radiata pine increment cores. FOR. SCI. 47(2):129–140.

Estimation of Mean Annual Temperature from Leaf and Wood Physiognomy - Michael C. Wiemann; David L. Dilcher; Steven R. Manchester (Forest Science, 2001)
There are distinct relationships among the anatomy of wood, the morphology of leaves, and the climate in which woody plants are growing. The relationships between leaf morphological characters and climate have been known for many years, but wood characters as climate indicators are less well studied. In this article, we use measurements of wood anatomy and leaf morphology from woody dicotyledonous plants, growing in Florida and Connecticut, to determine the accuracy to which statistical models can predict climate. The strength of the relationship between climate and physiognomy is important because it allows us to evaluate the phenotypic plasticity that woody plants express under various climates. In this study we use canonical correspondence and regression models to examine how precisely wood anatomical and leaf morphological characters are related to climate. For leaves, canonical correspondence analysis (CCA) using 31 characters gave the closest estimate of mean annual temperature (MAT) in Connecticut, whereas a regression equation using only a single leaf character (leaf margins with no teeth) as predictor gave the closest estimate in Florida. For wood, CCA using 13 wood characters gave the closest estimate in Florida, whereas a regression equation using only a single wood character (the occurrence of vessels smaller than 100 μm) gave the closest estimate in Connecticut. CCA showed that, although MAT has a smooth and continuous relationship with leaf physiognomy, this is not the case for wood. Temperate woods form a different physiognomic population than subtropical and tropical woods, in which the physiognomy of temperate woods is more strongly influenced by MAT than is the physiognomy of subtropical and tropical woods. FOR. SCI. 47(2):141–149.

A Longitudinal Study of Environmental Attitudes of Women and Gender Diversification in the U.S. Forest Service 1990–1996 - Greg Brown; Charles C. Harris (Forest Science, 2001)
The USDA Forest Service has been dominated by white, male foresters. Beginning in the mid-1970s, the agency was compelled legally and morally to begin diversifying its workforce by race, gender, and profession. Concurrent with workforce diversification efforts, the agency confronted demands from the courts, Congress, and interest groups to change national forest management by emphasizing national forest preservation over the production of commodities such as timber and livestock forage. This study examines the role of women as potential organizational change agents by analyzing survey data collected from two national studies of the Forest Service in 1990 and 1996. Results from the 1996 study indicate that women continue to exhibit higher levels of general environmental concern than men, suggesting their role as potential “saviors” in helping the agency to make the transition to increased emphasis on ecosystem management. Conversely, diversification of the Forest Service workforce continues to be highly contentious, with some employees feeling that the recruitment and promotion of women without adequate training and/or experience have left the agency unprepared to meet complex demands. The inability of the Forest Service to satisfy multiple, conflicting constituencies in the face of agency downsizing suggests the role of women as “scapegoats,” whose perceived lack of experience is responsible for agency shortcomings. The authors suggest that the historical convergence of workforce diversification with changes in national forest policy inevitably place women in the conflicting roles of both “saviors” and “scapegoats.” FOR. SCI. 47(2):246–257.

The Effect of Nitrogen Fertilization, Rock Type, and Habitat Type on Individual Tree Mortality - Guanghong Shen; James A. Moore; Charles R. Hatch (Forest Science, 2001)
An individual tree mortality model for nitrogen fertilized Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) stands was developed using data from permanent research plots located throughout the inland Northwest. The proposed linear logistic model included the following independent variables: a dummy variable for the two habitat types, a set of dummy variables for the five rock types, a set of dummy variables for the three N fertilizer treatments, diameter at breast height, crown ratio, and crown competition factor. The results show that N fertilization, rock type, and habitat type significantly affect individual tree mortality. The probabilities of tree mortality on fertilized plots were greater than those on control plots and increased with increasing N fertilizer application rates. Trees growing on granitic and metasedimentary rocks had lower foliar potassium concentration and exhibited greater probabilities of mortality than did those growing on other rocks. The probabilities of mortality for trees growing on sedimentary rocks were very low. Moist sites had lower soil fertility and produced higher mortality rates than dry sites. Furthermore, the N fertilization response ratio, defined as the annual mortality probability of a fertilized tree over the annual mortality probability of a unfertilized tree with identical tree and stand characteristics, was estimated based on the mortality model. The response ratios were nearly constant (about 1.4) across a range of tree diameters for all rock types with the 224 kg N treatment. The response ratios were also nearly constant (about 2.1) across a range of tree diameters for all rock types with the 448 kg N treatment. Finally, the mortality prediction model passed a validation test on independent data not used in model development. For. Sci. 47(2):203–213.

Reply: Influence of Vertical Foliage Structure on the Distribution of Stem Cross-Sectional Area Increment in Western Hemlock and Balsam Fir [For. Sci. 46(1):86–94] - John A. Kershaw (Forest Science, 2001)

Comment: Influence of Vertical Foliage Structure on the Distribution of Stem Cross-Sectional Area Increment in Western Hemlock and Balsam Fir [For. Sci. 46(1):86–94] - Harry T. Valentine (Forest Science, 2001)

Spatial Pattern Analysis in Plant Ecology - Harbin Li; Raija Laiho; Dan Binkley (Forest Science, 2001)

Linking Growth and Yield and Process Models to Estimate Impact of Environmental Changes on Growth of Loblolly Pine - V. Clark Baldwin; Harold E. Burkhart; James A Westfall; Kelly D. Peterson (Forest Science, 2001)
PTAEDA2 is a distance-dependent, individual tree model that simulates the growth and yield of a plantation of loblolly pine (Pinus taeda L.) on an annual basis. The MAESTRO model utilizes an array of trees in a stand to calculate and integrate the effects of biological and physical variables on the photosynthesis and respiration processes of a target tree on an hourly basis. PTAEDA2 sums the quantities for individual trees to obtain stand results; MAESTRO computes values for one tree at a time. These models were linked to provide a tool for further understanding stand, climatic, and edaphic effects on tree and forest productivity. PTAEDA2 predicts the characteristics of trees grown at a given stand density, on a given site, for a given length of time. These characteristics (outputs) are then used as direct inputs into MAESTRO which assesses the expected impact of environmental changes on tree function. The results from MAESTRO are fed back into PTAEDA2 to update future predictions by modifying the site index driver variable of the growth and yield model. An equation that predicts changes in site index as a function of net photosynthesis, age, and trees per unit area is the backbone of the dynamic linkage. The model changes required to link PTAEDA2 to MAESTRO were developed and reported earlier. This article reviews the earlier work and reports research results quantifying the relationships between net photosynthesis and the PTAEDA2 growth predictors, thus providing the basis for the MAESTRO to PTAEDA2 feedback process and integration of these two models. FOR. Sci. 47(1)77–82.

Biophysical Site Indices for Shade Tolerant and Intolerant Boreal Species - Chhun-Huor Ung; Pierre Y. Bernier; Frédéric Raulier; Richard A. Fournier; Marie-Claude Lambert; Jacques Régnière (Forest Science, 2001)
Two variants of a biophysical site index model were derived for two shade-tolerant boreal species (Abies balsamea [L.] Mill., and Picea mariana [Mill.] BSP), and two shade-intolerant boreal species (Populus tremuloides Michx., and Betula papyrifera Marsh.). The reduced model is based on the widely used assumption that the relationship between height and age of dominant trees depends solely on site properties: i.e., four climatic variables (degree-days, vapor pressure deficit, aridity index, and precipitation), and one edaphic variable (soil water-holding capacity). The full model is based on the further assumption that site index also depends on the stand successional stage represented by the dbh distribution index. The reduced model is accurate and unbiased for both intolerant species, but it becomes inaccurate and underestimates the mature stand dominant height for both tolerant species. The full model is equivalent to the reduced model for both intolerant species, but becomes two or three times more accurate and unbiased for both tolerant species. When incorporated into a growth and yield model as the site quality index, the reduced model performs as well as the traditional phytometric model (derived solely from an empirical fit of dominant height and age without any biophysical data) for both intolerant species, but it becomes biased for both tolerant species. By contrast, the full model, when used as a site quality index in the growth and yield model, is unbiased and equivalent to the phytometric model for the four species. These results show that the site index of intolerant species can be solely associated with climatic and edaphic variables, but these variables have to be completed by the successional stage for correctly estimating the site index of the tolerant species. FOR. Sci. 47(1):83–95.

Stand-Scale Correspondence in Empirical and Simulated Labile Carbohydrates in Loblolly Pine - David A. Sampson; Kurt H. Johnsen; Kim H. Ludovici; Timothy J. Albaugh; Chris A. Maier (Forest Science, 2001)
As investment into intensive forestry increases, the potential trade-offs between productivity and sustainability should be scrutinized. Because of their important role in internal carbon (C) budgets, labile C pools may provide a measure of the potential ability of trees and stands to respond to stress. We modified the process model BIOMASS to examine daily C budgets of midrotation nonfertilized and fertilized loblolly pine stands. We tested whether the absolute difference between daily simulated net canopy assimilation (GPP minus maintenance respiration) and our empirical estimates of production, or daily gross carbon balance, mimics the labile carbohydrate C pool. We compared this labile pool surrogate to independent, empirical analyses of total nonstructural (starch and soluble sugars) carbohydrates from an individual whole-tree analysis scaled to the stand level.Of particular interest, the simulated daily gross C balance indicated periods of carbon deficit during the growing season that lasted from 1 to 40 days. Simulated daily net C balance was met from labile C storage during these periods. Fertilized plots had similar time-period trends as the control plots, but exhibited a twofold increase in C assimilation and use. Simulated and empirical estimates of the labile carbohydrate pools displayed similar seasonal trends, although their correspondence depended on the time of year. Simulations indicated a winter/early spring “recharge” period; concentrations peaked at ~50 and ~60 mg C g biomass-1 in control and fertilized plots, respectively, in 1995. The overall correlation between predicted and empirical estimates was low to moderate (r = 0.51). The best agreement was with the empirical data from April through June as concentrations declined; however, predicted minimum concentrations (15 and 5 mg C g biomass-1 in control and fertilized plots, respectively) were lower, and obtained earlier in the year than the empirical data (~20 mg C mg biomass-1). These analyses quantify the strong extent that loblolly pine exhibits a buffered capacity to balance the C budget when current photosynthesis occasionally cannot meet daily C requirements. Further development of our approach may lead to a tool for analyzing potential risks associated with intensive forest management. FOR. Sci. 47(1):60–68.

Applying 3-PG, a Simple Process-Based Model Designed to Produce Practical Results, to Data from Loblolly Pine Experiments - Joe J. Landsberg; Kurt H. Johnsen; Timothy J. Albaugh; H. Lee Allen; Steven E. McKeand (Forest Science, 2001)
3-PG is a simple process-based model that requires few parameter values and only readily available input data. We tested the structure of the model by calibrating it against loblolly pine data from the Control treatment of the SETRES experiment in Scotland County, NC, then altered the Fertility Rating to simulate the effects of fertilization. There was excellent correspondence between simulated values of stem mass and the values obtained from field measurements, and good correspondence between simulated and measured stem diameters and Leaf Area Index values. Growth efficiency values derived from the model were similar to those obtained from field data. We used the model, without further calibration, to predict tree growth in terms of stem diameter at SETRES 2, a genotype × environment interaction trial in the same locality. Simulated mean stem diameters of two provenances did not differ significantly, over 3 yr, from those observed in the Control (unfertilized) treatments, but rates of change were lower than those of fertilized provenances. We then used 3-PG to simulate fertilized stand growth for an entire rotation length, and these results corresponded to those obtained with a traditional growth and yield model. This study showed that the model can simulate accurately the behavior and responses to environmental factors of loblolly pine and that it has considerable potential value as a management tool, for scenario analysis and as a research tool. FOR. Sci. 47(1):43–51.

Evaluation of Modeled Carbon Fluxes for a Slash Pine Ecosystem: SPM2 Simulations Compared to Eddy Flux Measurements - Kenneth L. Clark; Wendell P. Cropper; Henry L. Gholz (Forest Science, 2001)
A process-based model (SPM2) was developed to simulate net hourly exchanges of carbon for slash pine (Pinus elliottii var. elliottii) ecosystems in north-central Florida, and simulated values were compared to those obtained using eddy covariance measurements above the canopy. The SPM2 simulated relatively low hourly rates of net carbon exchange at high irradiance during the day, especially during the month of May. This discrepancy contributed the most to differences between the two approaches, and suggests that the model underestimates the maximum rate of leaf-level net photosynthesis during the period of rapid growth in the spring. The SPM2 also simulated lower net carbon release during the nighttime across the range of air temperatures, relative to eddy covariance measurements. As a result of these discrepancies, accumulated daytime and nighttime sums were quite different between the two approaches. However, once results were aggregated over 24 hr, differences between simulations and measurements were insignificant at all but the highest and lowest daily net carbon gain values. Annual estimates for 1996 were similar: 693, 719, and 745 g C m-2 yr-1 for the SPM2 model, eddy covariance measurements and mass balance measurements, respectively. This model evaluation has lead to specific research questions for guiding further model development. FOR. Sci. 47(1):52–59.

The Effects of Ozone on a Lower Slope Forest of the Great Smoky Mountain National Park: Simulations Linking an Individual Tree Model to a Stand Model - D.A. Weinstein; B. Gollands; W.A. Retzlaff (Forest Science, 2001)
We used an individual tree physiology model, TREGRO, and a stand succession model, ZELIG, to extrapolate from the direct response of leaf photosynthesis to ozone exposure in individual plants to an estimate of the possible future ozone effects on a forest located in the Twin Creeks region in Great Smoky Mountains National Park (GSMNP). This forest is dominated by yellow-poplar (Liriodendron tulipifera L.). With TREGRO, we estimated whether the reduction in the supply of carbon caused by ozone exposure would prevent an individual tree from meeting its demands for carbon for growth. With ZELIG, we analyzed the effect that changes in individual tree growth have in altering the ability of trees to successfully compete during forest succession. Current ambient levels of ozone measured at mid-elevations on the west side of GSMNP were predicted to reduce the abundance of yellow-poplar by 10% over the next 100 yr. This reduction would accelerate declines that are expected because of natural successional change. An increase of ozone of 50% above current ambient conditions was predicted to decrease yellow-poplar abundance by 30%. A reduction of ozone to halfambient levels was insufficient to prevent yellow-poplar abundance decreases. Increases in abundance in two other canopy dominants, red maple (Acer rubrum L.) and black cherry (Prunus serotina Ehrh.) were predicted from the release from competition as yellow-poplar was suppressed by ozone exposure. These increases, however, were predicted to be short-lived, with large decreases of up to 30% eventually occurring for both species. Overall basal area of the forest was predicted to be relatively unchanged by ozone exposure. FOR. Sci. 47(1)29–42.

Ideotype Development in Southern Pines: Rationale and Strategies for Overcoming Scale-Related Obstacles - Timothy A. Martin; Kurt H. Johnsen; Timothy L. White (Forest Science, 2001)
Indirect genetic selection for early growth and disease resistance of southern pines has proven remarkably successful over the past several decades. However, several benefits could be derived for southern pine breeding programs by incorporating ideotypes, conceptual models which explicitly describe plant phenotypic characteristics that are hypothesized to produce greater yield. The potential benefits of using ideotypes include improvement in trait heritabilities and genetic correlations, higher genetic gain in diverse silvicultural environments, guidance for developing mating designs, and provision of a framework for synthesis of tree production physiology knowledge. There are numerous obstacles to the development of ideotypes for southern pines, most of them related to the difficulty of linking traits and processes that operate at small spatial and temporal scales (e.g., tree crown morphological traits or leaf net photosynthesis) with outputs that occur at large spatial and temporal scales (e.g., stand-level, rotation-age stem biomass yield). Fortunately, as we enter the 21st century, several relevant advances are converging that bode well for overcoming these obstacles. These advances relate to improvements and developments of process modeling, advances in technologies that permit measures of component processes at relevant scales, the likely future importance of intensive clonal forestry, and the movement toward large-scale genetic block plot experiments. FOR. Sci. 47(1):21–28.

Modeling Annual Carbon Uptake for the Indigenous Forests of New Zealand - David Whitehead; John R. Leathwick; Adrian S. Walcroft (Forest Science, 2001)
A regional estimate of annual gross carbon uptake for the indigenous forests of New Zealand is presented. Carbon uptake for forest canopies occupying 59,311 sites on a 1 km grid (25% of the total land area) is estimated daily using a leaf-level photosynthesis–stomatal conductance model with appropriate scaling procedures (Leuning et al. 1995), and a model of site water balance. For each site, estimates of monthly climate data, soil physical properties, root-zone depth, and nitrogen availability were matched from maps. Forest type was distinguished into 18 classes and values for the maximum rate of carboxylation, Vcmax0, were assigned according to the ratio of conifer to broadleaved trees and nitrogen availability. Mean annual carbon uptake across all sites was 1.5 kg m-2. Variability between sites was attributable principally to the value for Vcmax0, followed by temperature. The effects of water stress integral, air saturation deficit, and solar radiation on carbon uptake were much less. Mean radiation conversion efficiency (ratio of carbon uptake to intercepted solar radiation) was low at 0.79 kg GJ-1, consistent with low nitrogen availability. The analysis highlights the sensitivity of carbon uptake to physiological characteristics and nitrogen status and thus the need to determine values for photosynthesis parameters for trees growing in field conditions. FOR. Sci. 47(1):9–20.

Process Models as Tools in Forestry Research and Management - Kurt Johnsen; Lisa Samuelson; Robert Teskey; Steve McNulty; Tom Fox (Forest Science, 2001)
Forest process models are mathematical representations of biological systems that incorporate our understanding of physiological and ecological mechanisms into predictive algorithms. These models were originally designed and used for research purposes, but are being developed for use in practical forest management. Process models designed for research typically require complicated and intensive data, whereas models designed for management strive to use simpler and more readily available data and provide predictions useful for forest managers. In this article, we review some different types of process models, examine their requirements and utility in research and forest management, and discuss research priority areas that will increase their accuracy and application. We conclude that soil and nutritional limitations are the most difficult model components in predicting growth responses using process models. FOR. Sci. 47(1):2–8.

Potential Effect of Stand Structure on Belowground Allocation - Thomas J. Dean (Forest Science, 2001)
Stand structure affects two key variables that affect biomass allocation to the stem: leaf area and height to the center of the crown. By translating wind forces into a bending moment, these variables generate bending stress within a stem. The uniform-stress axiom of stem formation can be used to calculate current stem mass for a given bending moment and stem allocation for changes in bending moment over a time period. Stem allocation probably affects allocation to fine roots since the stem precedes the root system on the chain of carbohydrate sinks, and total net primary production is a linear function of leaf area. This study indirectly supports this link between stand structure and belowground allocation. A regression model based on the relationship between bending moment and stem allocation explained 98% of the variation in stand-level stem production of a 12-yr-old loblolly pine (Pinus taeda L.) plantation subjected to factorial combinations of irrigation and fertilization. Further-more, relative fine-root allocation was inversely related to relative stem allocation and increases in apparent bending stress. Corresponding associations between bending stress and relative allocation between the stem and fine roots appear to exist for other species, providing additional support for the proposed link. FOR. Sci. 47(1):69–76.

Hydrologic Modeling of a Drained Pine Plantation on Poorly Drained Soils - Devendra Man Amatya; Richard Wayne Skaggs (Forest Science, 2001)
Three experimental watersheds in eastern North Carolina have been continuously monitored since 1988 to study long-term hydrology of loblolly pine (Pinus taeda L.) forests on poorly drained soils. This study was conducted to test the forestry version of an agricultural hydrology model DRAINMOD with 10 yr (1988–1997) of data collected at one of these watersheds under conventional (open ditch) drainage. The model, which is based on hourly water balance for the land between parallel drainage ditches, simulates interception, evapotranspiration (ET) as the sum of canopy transpiration and soil evaporation, drainage, and surface runoff. Results showed that model predictions of daily water table elevations and flow rates on an average annual basis were within 0.15 m and 0.61 mm, respectively, compared to the measured data. Relative errors on drainage outflow varied from -18% to 23%, with an average of 0.4%. Errors in measured flow rates during weir submergence, missing rainfall and weather data, and uncertainty in estimates of stomatal conductance contributed to the differences between model predictions and field observations. It was concluded that the model is a reliable tool for assessing hydrologic impacts of silvicultural and water management treatments, as well as climate changes, on these pine stands. FOR. Sci. 47(1):103–114.

Nutrient Supply and Fertilization Efficiency in Midrotation Loblolly Pine Plantations: A Modeling Analysis - Mark Ducey; H. Lee Allen (Forest Science, 2001)
We simulated the 10 yr macronutrient budgets for 14 installations in a regionwide midrotation loblolly pine (Pinus taeda L.) fertilization study using NUTREM, a simplified model of carbon and nutrient uptake and distribution. Each installation includes 2–4 replications of N and P addition in a two-way factorial design. By approximating the constraints on nutrient use as elements in a linear programming problem, and estimating the parameters of the problem using least squares, we were able to identify baseline soil supply rates and fertilization efficiencies for N and P for each installation. Estimated N supply ranged from 47 kg ha-1 yr-1 to 103 kg ha-1 yr-1, while P supply ranged from 5.5 to 12.4 kg ha-1 yr-1. Fertilization efficiencies were extremely variable, ranging from 23% to 100% for N and 0% to 78% for P. A lower bound to the baseline supply rate was identified for K, Ca, and Mg for each site. While only three sites were P-limited, P limitation was imminent on all sites with operational doses of applied N. While the accuracy of NUTREM is limited by the availability of basic process-level data, the method suggests possibilities for predicting growth response to nutrient amendments. FOR. Sci. 47(1):96–102.

Measuring the Performance Improvement of Taiwan Forests after Reorganization - Chiang Kao (Forest Science, 2000)
The data envelopment analysis (DEA) approach has been widely applied to measure the relative efficiencies of decision making units (DMUs) for a time period. This article measures the performance improvement of a DMU at two time points by using the DEA approach. Two ideas are proposed. One is to treat one DMU at two time points as two different DMUs, and the ratio of the efficiency scores of a DMU at two time points serves as a measure of the efficiency improvement. The other is to calculate the Malmquist productivity index of a DMU to represent its productivity improvement. Both the efficiency ratio and the productivity index can be decomposed into the technical part and the scale part. From the data of the eight forest districts of Taiwan compiled in 1989 and 1992, the efficiency and productivity improvement in these two periods are measured. The results of the two methods are consistent in that both indicate a slight improvement in performance. FOR. SCI. 46(4):577–584.

A Review of Past Research on Dendrometers - Neil A. Clark; Randolph H. Wynne; Daniel.L. Schmoldt (Forest Science, 2000)
The purpose of a dendrometer is to measure tree diameter. Contact and noncontact dendrometers accomplish this task by collecting different metrics, including girth or distance between tangent points on a tree stem. Many dendrometers have been developed in the last quarter century and many have been retired. This article summarizes instrument developments and application results, contains an interpretation of the results, and provides guidance for dendrometer selection. FOR. SCI. 46(4):570–576.

Alternative Measurements of Productive Efficiency in the Global Bleached Softwood Pulp Sector - Runsheng Yin (Forest Science, 2000)
In this article, we conduct a productive efficiency analysis using the two major methods: stochastic frontier analysis (SFA) and data envelopment analysis (DEA). First, we demonstrate the steps and assumptions involved in SFA and DEA, and highlight their strengths and weaknesses. Then we apply them to the case of bleached softwood kraft pulp production to derive technical and allocative efficiency measures for 102 mills in the world. We find that in general, the SFA cost-efficiency levels are higher than their DEA counterparts, and much of the cost inefficiency is caused by inappropriate input mix, or allocative inefficiency, instead of the way with which inputs are converted into outputs, or technical inefficiency. In addition, SFA and DEA results rank some of the producers in different orders. We also find that while cost-efficiency levels vary in different regions, most producers have substantial opportunities to make improvements. Finally, we discuss implications of our study. FOR. SCI. 46(4):558–569.

Estimating Metrics of Forest Spatial Pattern from Large Area Forest Inventory Cluster Samples - Christoph Kleinn (Forest Science, 2000)
The interest in ecologically meaningful information from forest inventories is increasing. Forest area and its characteristics of spatial distribution are among this information. This paper describes a technique for deriving some metrics of forest spatial pattern from nonmapped forest inventory samples. The technique is developed for clusters of subplots, though applicable also for other plot types. It evaluates the area of the three categories: forest, nonforest, and buffer, estimated by the percentage of cluster plots where all, none, or some subplot centers fall into forest. Of particular interest is the buffer area, which is an imagined strip along the forest boundary: the larger this area, the more forest boundaries there are, and the more fragmented the forest pattern is. The estimates of forest and buffer area percentage are used to derive metrics that are related to perimeter length and mean patch size. Variance estimators for these metrics are given. Two examples are presented to illustrate the characteristics of the method, one with a schematic map, one with real inventory data. The most meaningful results are obtained when the size of the cluster plots used is smaller than the forest patches and smaller than the distance between them. The examples suggest that, in order to obtain reasonably precise estimates, sample size should be n = 500 or more. These conditions commonly hold in large area forest inventories. The technique processes information that is readily available from the field measurements of large area forest inventories. It does not require extra measurements and adds an ecologically meaningful aspect to the data analysis. It is independent of the availability of complete maps of the inventory region or of mapped plots, and therefore also allows the retrospective analysis of old forest inventory sample data. FOR. SCI. 46(4):548–557.

An Econometric Analysis of Norwegian Sawmilling 1974–1991 Based on Mill-Level Data - Sjur Baardsen (Forest Science, 2000)
An eight-input translog total cost function was estimated, and the estimates were used to calculate Allen and Morishima substitution elasticities, price elasticities of conditional input demands, elasticity of size, and technical change for Norwegian sawmilling at a five-digit disaggregate industry level, based on an unbalanced panel of 3,090 individual observations of sawmills over the period 1974–1991. The unusually rich source of data made it possible to analyze the production economics of sawmilling in more detail than has ever been possible before. As far as comparisons with other studies could be made, many of the Allen substitution elasticities and price elasticities of conditional input demand were in accordance with previous findings. The inputs were found to be inseparable. Therefore, frequently used overall aggregates like “materials” and “energy” are not to be recommended. Since the average sawmill had economies of size yet to be exploited, it would have been better off by increasing its size. The most effective way of doing this is to use relatively more sawlogs, electricity, capital, and the aggregate other inputs, and relatively less labor, lumber input (for planing), and the aggregate input other materials. The rate of technical change was negative for the average sawmill. FOR. SCI. 46(4):537–547.

Persistence of Growth Variation in Tree-Ring Chronologies - Seung Jick Yoo; Brian D. Wright (Forest Science, 2000)
We infer baseline response to climate of the growth of trees in California dendroclimatological samples, adopting linear and nonlinear approaches and using the expected accumulated impact of a state change as one measure of persistence. Many samples exhibit two quite distinct growth states. Timing of high and low growth states is highly heterogeneous across locations, and regional aggregation seriously understates the size and persistence of local growth changes. If climate is a dominant factor in local tree growth, then local climate is not well represented by an aggregate regional index. FOR. SCI. 46(4):507–520.

A Travel Cost Analysis of Nonconsumptive Wildlife-Associated Recreation in the United States - William T. Zawacki; Allan Marsinko; J.M. Bowker (Forest Science, 2000)
Increased emphasis on sustainable resource management in forestry has effectuated a demand for various nontimber values. Nonconsumptive wildlife recreation is an important nontimber service produced on forest and rangeland. Travel cost models and data from the 1991 National Survey of Fishing, Hunting and Wildlife-Associated Recreation are used to estimate the demand and value for nonconsumptive wildlife-associated recreation in the United States. Resulting welfare measures are shown to be sensitive to assumptions about the cost of travel time, pecuniary costs, and functional form. Consumer surplus estimates range from 18.7 to 327.5 dollars per trip, while aggregate estimates of consumer surplus resulting from access to nonconsumptive wildlife recreation range from 5.8 to 66.4 billion dollars annually. Availability of information about nonparticipants allows comparison of truncated and untruncated demand models. Contrary to previous findings, consumer surplus estimates from truncated models are smaller than for untruncated counterparts. Trip demand is found to be adversely affected by per capita decreases in forest and rangeland. Models include interaction variables to avoid forcing hunting or fishing as potential substitutes for the large number of people who do not hunt or fish. Hunting and nonconsumptive wildlife recreation are complementary activities, while the results for fishing are mixed. FOR. SCI. 46(4):496–506.

Determination of Stand Properties in Boreal and Temperate Forests Using High-Resolution Imagery - H.H. Shugart; Laura Bourgeau-Chavez; E.S. Kasischke (Forest Science, 2000)
The existence of a relatively long (ca. 40 yr) satellite imagery archive for examination of potential worldwide forest change motivated an inspection of the relation between forest features observable from higher resolution airborne and satellite imagery and measures of forest biomass, height, and age. Using these data, we inspected the relation between stand age, mean diameter, height, and standing aboveground biomass for forest stands located in boreal forest (near Fairbanks, Alaska) and temperate forest (near Durham, North Carolina). The features of a spatial statistic, semivariance, prove to be related to the structure, age, and biomass patterns of these forests. These initial results indicate the feasibility of using appropriately calibrated high-resolution satellite imagery to estimate and monitor aboveground carbon reserves of forests. FOR. SCI. 46(4):478–486.

Centroid Method: Comparison of Simple and Complex Proxy Tree Taper Functions - Dean W. Coble; Harry V. Wiant (Forest Science, 2000)
Cubic-meter volumes estimated from simple and complex proxy taper functions were compared to observed volumes of loblolly pine (Pinus taeda, L.) and ponderosa pine (Pinus ponderosa, Dougl. ex Laws.) trees to evaluate accuracy (bias and precision) in the centroid method. The results of this investigation showed no clear evidence that a more complex proxy taper function is more accurate than a simple function. The results also support previous studies that show accurate volumes of standing trees may be obtained using the centroid method, which requires only one upper-stem diameter measurement. FOR. SCI. 46(4):473–477.

Root Chemistry of Mature Douglas-Fir Differs by Habitat Type in the Interior Northwestern United States - James A. Moore; Peter G. Mika; Terry M. Shaw (Forest Science, 2000)
Carbon compound concentrations in plant tissues depend on the environment in which plants grow. However, little is known about how these concentrations vary across a range of forest environmental conditions. Our study examined root tissue (phloem, cambium, phellum, and phello-derm) collected from naturally regenerated mature Douglas-fir (Pseudotsuga menziesii var. glauca [Bessn.] Franco) trees in eight stands on three habitat type series encompassing a range of temperature and moisture conditions. The objective was to determine root chemical composition (sugar, starch, phenol, and tannin) differences among the habitat types. Douglas-fir roots collected from dry, warm Douglas fir habitat types had sugar concentrations of 4% compared to 3% for roots from cool, moist habitat types. Root samples collected from Douglas-fir habitat types showed tannin concentrations about double those from grand fir or western redcedar habitat types. Phenol/tannin ratios for the cool, moist habitat types were about double those from warm, dry Douglas-fir habitat types. Roots sampled from western redcedar habitat types had phenol concentrations and phenol/sugar ratios more than 50% higher than those from Douglas-fir and grand fir habitat types. We speculate that root chemistry of Douglas-fir growing on Douglas-fir habitat types could make them more drought resistant but less disease resistant, while Douglas-fir growing on western redcedar types would be less drought resistant but more disease resistant. Douglas-fir growing on warm, dry sites allocated more carbon to tannin production and less to phenols. FOR. SCI. 46(4):531–536.

Emergy Evaluation of Reforestation Alternatives in Puerto Rico - Howard T. Odum; Steven J. Doherty; Frederick N. Scatena; Pushker A. Kharecha (Forest Science, 2000)
Six alternative ways of reforesting degraded lands in Puerto Rico were evaluated using emergy (spelled with an “m”). Emergy and its economic equivalent, emdollars, put the contributions of environmental work and human services on a comparable basis. This article shows the emergy method for evaluating forest contributions to public benefit and its use to select alternatives for reforestation. Emdollar values were compared for six scenarios for reforestation of degraded land in Puerto Rico: (1) the natural succession within or adjacent to mature forest; (2) reforestation from the spread of the exotic tree siris (Albizia lebbek); (3) reforestation with plantations of siris and mahogany for harvest; (4) reforestation by leaving plantations unharvested; (5) direct planting of seedlings of many species; and (6) starting patches of forest by massive transfer of topsoil, seed bank, and roots. After energy systems diagrams were made for each reforestation alternative, data were assembled and evaluation tables prepared that estimated the emergy required for: (1) canopy closure and (2) developing species complexity if left unharvested. To explain the method, detailed calculations were included for one of the alternatives, exotic Albizia lebbek plantation on 11 yr harvest cycle.All alternatives generated net public benefit (emdollar yield ratios 4.2 to 24.3). The emdollar value of a closed canopy developed in 10 to 20 yr ranged from 20,000 to 48,000 em$ /ha, whereas the economic costs were $1200 to $9700. For complex forest development in 25 to 60 yr, values ranged from 63,000 to 118,000 em$ /ha, much higher than economic costs of $4000 to $12,000/ha. Highest public benefit per dollar cost came from succession (24.7 em$/$) and exotic colonization (19.1 em$/$). Highest potential monetary returns were from exotic spread (15.1 $/$) and plantations (17.9 and 14.5 $/$). Stand quality after 60 yr, as measured by the transformity (emergy/energy), was largest in mahogany plantation (6.4 × 10 4 sej/J) and succession forest (3.9 × 104 sej/J). FOR. SCI. 46(4):521–530.

Genotypic Stability and Genetic Parameters for Growth and Biomass Traits in a Water × Temperature Factorial Experiment with Pinus sylvestris L. Seedlings - Johan Sonesson; Gösta Eriksson (Forest Science, 2000)
The objective of this experiment was to study genotypic stability for growth and biomass traits recorded in treatments with optimal and limiting water availability at two different temperatures and to study how the different growth environments affected genetic parameter estimates. Open-pollinated families of Scots pine (Pinus sylvestris L.) were collected in 2 seed orchards with 28 and 35 families respectively and cultivated for 1 growth period in a growth chamber. Heritability estimates were generally moderate–high (h2 = 0.3–0.8) for growth traits in individual treatments. Joint analyses of all treatments revealed significant family × temperature and family × temperature × water regime interactions. Family × water regime interaction and family effects were not significant. The results indicate low adaptation to water availability and a higher adaptation to different temperatures in the two Swedish Pinus sylvestris populations. If we assume that our results hold for a large part of the rotation the G × E interactions imply that climate change can alter the ranking of clones in a breeding program and thus decrease genetic gain. Studies of family ecovalence values showed that a minority of families (4–31%) contributed significantly to the interactions. Selection for stability could be a possible way to reduce the negative effects of G × E interaction. FOR. SCI. 46(4):487–495.

Differential Effects of Rhizobacterial Strain and Dose on the Ectomycorrhizal Colonization of Loblolly Pine Seedlings - J.D. Vonderwell; S.A. Enebak (Forest Science, 2000)
Loblolly pine seed were inoculated at sowing with one of four plant growth-promoting rhizobacteria (PGPR) strains at four different rates both in the nursery and in the greenhouse. Seedlings were harvested at 4, 8, and 12 wk after sowing in the greenhouse and at 5, 10, and 15 wk after sowing in the nursery. Ectomycorrhizae colonization, estimated as the total number ectomycorrhizal roots per seedling and averaging by gram root biomass, were not evident on any treatment at either 5 wk in the nursery or 4 wk in the greenhouse. However, by 8 wk after sowing, many treatments significantly (P < 0.0001) inhibited ectomycorrhizal root formation. Generally, increasing the rate of all bacteria applied in the greenhouse decreased ectomycorrhizal root formation. Conversely, strain LS212 at 1011 cfu resulted in an increase in ectomycorrhizal roots in the nursery. Increases in seedling root growth were also dependent on bacterial strain and rate, whereas shoot biomass was not effected. Decreases in ectomycorrhizae colonization accounted for 61% of the variation in increases in root biomass, suggesting high metabolic costs of mycorrhizal maintenance in the presence of some rhizobacteria. However, differences in shoot height and survival after outplanting could not be attributed to the mycorrhizae colonization effect. These studies demonstrate that mycorrhizae may serve as a carbon sink early in seedling development and indicate a complex interaction between soil microflora and bacterium in nursery and greenhouse settings. FOR. SCI. 46(3): 437–441.

Comparing Adjacency Constraint Formulations for Randomly Generated Forest Planning Problems with Four Age-Class Distributions - Marc E. McDill; Janis Braze (Forest Science, 2000)
Three types of adjacency constraint formulations—pairwise, Type I ND (nondominated), and NOAM (new ordinary adjacency matrix)—were compared on 900 hypothetical, randomly generated, spatially explicit forest management problems with between 50 and 350 stands. Forests were generated using four age-class distributions, nominally called immature, regulated, overmature, and old-growth. Management planning problems with adjacency constraints were formulated for these forests in Model 1 format based on a planning horizon consisting of three 20 yr periods. The problems also included flow constraints and minimum average age requirements for the ending forest. For all age-class distributions, the Type I ND constraint type resulted in significantly lower solution times than either the Pairwise or the NOAM constraint types. NOAM constraints performed better than Pairwise constraints for immature forest problems, but Pairwise constraints performed better than NOAM constraints for overmature and old-growth forest problems. There was no difference between these two constraint types for regulated forest problems. Results also show that the age-class distribution of the forest is one of the most important factors determining the time needed to solve forest management problems with adjacency constraints. In general, the more mature the forest, the harder the problem is to solve. In particular, problems based on the old-growth age-class distribution typically took much longer to solve than comparable problems based on the other age-class distributions. FOR. SCI. 46(3): 423–536.

Calibrating Predicted Diameter Distribution with Additional Information - Annika Kangas; Matti Maltamo (Forest Science, 2000)
The diameter distribution of the growing stock is an essential starting point in many forest management planning problems. There are several methods for predicting the diameter distribution of a stand, varying from methods which utilize theoretical distribution functions to nonparametric methods. Usually the predicted diameter distribution is scaled so that the stem number corresponds to the measured value. However, if stem number and basal area are both known, it may be difficult to predict a distribution that gives correct estimates for both these characteristics. Such diameter distributions can be obtained using an approach adopted from sampling theory—calibration estimation. In this study, the diameter distributions of Scots pine were predicted with two different methods, the Weibull and percentile based methods, and then calibrated with additional information. The calibration reduced the RMSE of stand variables computed from the predicted distribution. FOR. SCI. 46(3): 390–396.

Linking Harvest Choices to Timber Supply - Jeffrey P. Prestemon; David N. Wear (Forest Science, 2000)
Aggregate timber supply by ownership was investigated for a small region by applying stand-level harvest choice models to a representative sample of stands and then aggregating to regional totals using the area-frame of the forest survey. Timber harvest choices were estimated as probit models for three ownership categories in coastal plain southern pine stands of North Carolina using individual permanent and remeasured stand-level data from last two available USDA Forest Service Forest Inventory and Analysis (FIA) surveys. The timber harvest decision was modeled as a function of timber values, a cost factor, and stand volume as a proxy for nontimber values. Probit models were statistically significant at 1% for all ownerships. Area expansion factors (the portion of forest area in the region represented by the sampled stand) were then combined with harvest probabilities to model the aggregate effects of price changes on timber supply, given a fixed forest area. Implied price elasticities were estimated using this modeling of aggregate effects, and a bootstrapping procedure was applied to estimate confidence limits for supply elasticities with respect to price. Our results showed that NIPF and industry were elastically responsive in the aggregate when price increases are perceived as temporary but much less elastically and usually negatively responsive when increases are perceived as permanent. Results are consistent with theory of optimal rotations and highlight the critical influence of both existing inventory structure and expectations on aggregate timber supply. FOR. SCI. 46(3): 377–389.

Predicting Future Forestland Area: A Comparison of Econometric Approaches - SoEun Ahn; Andrew J. Plantinga; Ralph J. Alig (Forest Science, 2000)
Predictions of future forestland area are an important component of forest policy analyses. In this article, we test the ability of econometric land use models to accurately forecast forest area. We construct a panel data set for Alabama consisting of county and time-series observation for the period 1964 to 1992. We estimate models using restricted data sets—namely, data from early periods—and use out-of-sample values of dependent and independent variables to construct precise tests of the model's forecasting accuracy. Three model specifications are examined: ordinary least squares, dummy variables (fixed effects), and error components (random effects). We find that the dummy variables model produces more accurate forecasts at the county and state level than the other model specifications. This result is related to the ability of the dummy variables model to more completely control for cross-sectional variation in the dependent variables. This suggests that the estimated model parameters better capture the temporal relationship between forest area and economic variables. FOR. SCI. 46(3): 363–376.

A Method of Estimating Direct and Indirect Effects of Armillaria Root Disease and Other Small-Scale Forest Disturbances on Canopy Gap Size - John E. Lundquist (Forest Science, 2000)
The ecological and economic impacts of individual forest pathogens on forest stands are often difficult to measure because of indirect impacts arising from their interactions with other agents. Root diseases especially interact with many elements of the forest. This study uses a method called path analysis to estimate direct and indirect effects of Armillaria root disease and other small-scale disturbances on a pristine Pinus ponderosa stand in the Black Hills of South Dakota. Indirect effect was defined as an outcome where one small-scale disturbance alters the effect that another has on canopy gap size. Results indicate that key factors affecting gap size include Armillaria root disease, bark beetles, weak pathogens, ice/snow damage, lightning, and wildfires, presented in order of relative importance. Interactions occur between Armillaria and lightning, beetles, wind, and fire; between bark beetles and wind, fire, and weak pathogens; and between wind and fire. Armillaria and beetles both tend to occur where damage by wind is absent. Armillaria root disease was predicted to have the largest overall effect on gap size, which is mostly due to its direct effects, and not resulting from its interactions with other disturbances. Path analysis generates a predictive model based on covariation among disturbances and offers a way of quantifying the effects of these associations. FOR. SCI. 46(3): 356–362.

Perceived Ecological Risks to Water Environments from Selected Forest Industry Activities - Nigel Cavanagh; Timothy McDaniels; Lawrence Axelrod; Paul Slovic (Forest Science, 2000)
This article examines underlying factors shaping lay perceptions, and differences between lay and expert perceptions, of the ecological risks to water environments associated with six forest industry activities. A survey was administered to 183 lay subjects in four communities within the Lower Fraser Basin of western Canada. Parts of the survey were also administered to 16 aquatic science professionals. The results show that both lay and expert respondents generally perceive that clearcut logging and effluent from pulp mills pose a high degree of risk, while selective logging poses a lesser degree of risk. Both groups believe that fertilizer use poses a risk to water quality. However, the experts viewed the construction of logging roads as posing significantly more risk to water environments, and requiring greater regulation, than did the lay respondents. Conversely, the lay respondents viewed pesticide use as posing significantly more risk to water environments, and requiring greater regulation, than did the expert respondents. Discussion about the implications of these perceptions in terms of policy issues and communication efforts complete the article. FOR. SCI. 46(3): 344–355.

Water and Nutrient Movement in Small, Forested Watersheds in the Boston Mountains of Arkansas - Garland L. Wheeler; Kenneth F. Steele; Edwin R. Lawson (Forest Science, 2000)
Four small (< 13.5 ha), upland, hardwood watersheds were selected for a study of the changes in water dynamics and associated chemical changes as water moves through various components of the ecosystem. These watersheds were also used to determine what changes in water movement and chemistry are related to silvicultural treatments of conversion to pine, a shelterwood cut or a clearcut applied 6 yr earlier. A fourth watershed served as a control. It was estimated that 29% of the rainfall left the watersheds. The ratio of Na+ and Cl- indicated a marine source of these elements. Enrichment from terrestrial sources was indicated for Mg+2, Ca+2, K+, and SO42-.The major changes in water movement and in water chemistry occurred between the surface of the litter layer and the bottom of the A horizon where 55% of the water and most of the nutrients that entered the watersheds were absorbed by a root network that develops at the litter A horizon interface. The degree of absorption varied from 30% for Na+ to 86% for H+. In general, nutrients that passed the A horizon also passed the E horizon and were transported out of the watersheds. SO42- was the major nutrient deposited (21.5 kg ha-1) and accumulated (15.6 kg ha-1) in the watershed followed by NO3- (9.8 and 8.2 kg ha-1) and Ca+2 (9.6 and 5.6 kg ha-1). Cl- behaved differently than other nutrients because it was stored in the canopy and surface soil layers but lost from deeper zones in the watershed. Mg+2 also differed in that it was the only nutrient to have a net loss from the watersheds.Magnesium, K+, H+, and NO3- had differences related to silvicultural treatments. Magnesium was leached from the canopy in the control and shelterwood. K+ was enriched in the throughfall of the control and possibly shelterwood. Hydrogen was absorbed in the control canopy and leached from the clearcut canopy. FOR. SCI. 46(3):335–343.

Modeling the Size–Density Relationship in Direct-Seeded Slash Pine Stands - Quang V. Cao; Thomas J. Dean; V. Clark Baldwin (Forest Science, 2000)
The relationship between quadratic mean diameter and tree density appeared curvilinear on a log–log scale, based on data from direct-seeded slash pine (Pinus elliottii var. elliottii Engelm.) stands. The self-thinning trajectory followed a straight line for high tree density levels and then turned away from this line as tree density decreased. A system of equations was developed to model the reciprocal effects of stand diameter and density through time. The equations performed well for these data. Since the model is constrained according to the self-thinning rule, it should provide reasonable extrapolation. FOR. SCI. 46(3):317–321.

The Economics of Prescribed Burning: A Research Review - Hayley Hesseln (Forest Science, 2000)
Prescribed burning has, in the past decade, become the focus of debate among policy makers, federal and private land managers, and the public. To manage fire effectively, the USDA Forest Service has formally recognized the need for economic analysis. It is stated in the Federal Wildland Fire Policy of 1995 that fire management alternatives will be based on science and sound ecological and economic principles. This article briefly examines key issues of the Federal Wildland Fire Policy from an economic perspective, and reviews the economic literature pertaining to prescribed burning. In particular, attention is paid to research regarding costs and benefits, efficiency, risk, and the wildland–urban interface. Recommendations for future economic research include focusing on defining a production function that relates economic and ecological outcomes with respect to prescribed fire; assessment of long-term cumulative effects; and finally, a comprehensive assessment of risk including decision making at the agency level. FOR. SCI. 46(3):322–334.

The Engines of Change in Rsource-Dependent Communities - Jo Ellen Force; Gary E. Machlis; Lianjun Zhang (Forest Science, 2000)
Social scientists have long attempted to understand change in natural resource-dependent communities. This article examines the relationship of three alternative “engines of change”: local resource production, local historical events, and broad societal trends. Regression models were used to examine the relationships between four dimensions of community social change (size, structure, cohesion, and anomie) and the alternative “engines of change” in seven resource-dependent communities in the Pacific Northwest for over 50 year time periods. Included in the group were four timber towns, as well as communities dependent upon fishing, tourism, and mining. The data suggest that broad societal trends followed by local historical events explain the largest proportion of the variation in community social change dimensions of size and structure. Local resource production has modest explanatory power when combined with the other “engines of change.” FOR. SCI. 46(3): 344–355.

A Solution Method for Uneven-Aged Management Applied to Norway Spruce - Peder Wikström (Forest Science, 2000)
The uneven-aged management problem is to determine the management regime for an existing stand over an infinite time horizon, without ever clearcutting it. A new solution method to solve this problem is presented and demonstrated on simulated Norway spruce stands with different initial stand structures. Diameter distributions were used as a convenient way to describe these structures. The method, which puts much effort into determining the timing of harvest activities, is based on Tabu search and greedy heuristics. The growth dynamics were described with a single tree simulator. Different problem approaches for this problem were adopted to maximize the net present value (NPV) of harvested trees, with or without steady-state constraints. With no such constraints, a finite time horizon approximates the general management problem, while the steady-state constraints involved fixed and equilibrium endpoints. The fixed endpoint was a reverse J-shaped diameter distribution, and its purpose was to mimic the structure of a virgin stand. Analysis of economic efficiency, productivity. and managerial implications were made. With the method used and for the endpoint problems, the conversion strategy, conversion length. and steady-state diameter distribution were determined simultaneously. The Kolmogorov-Smirnov measure was used to describe the similarity between diameter distributions and was put directly into the constraints. The infinite approximation is suggested as the best problem formulation as it, in contrast to a steady-state approach, does not assume that a resource system reaches a climax, eliminates the need to define a diameter class width, and involves no fixed cutting cycles. The even-aged management problem, which is to determine the best period for clearcutting and the best thinning regime that precedes the clearcut, while recognizing the soil expectation value, was analyzed for comparison. The method is flexible, independent of the kind of growth simulator used, and can, for example, be directly applied to a diameter class model. FOR. SCI. 46(3): 452–463.

A Timing-Oriented Approach to Spatial Allocation of Fire Management Effort - John Hof; Philip N. Omi; Michael Bevers; Richard D. Laven (Forest Science, 2000)
This article explores spatial optimization approaches to fire (and possibly fuel) management problems, with a timing-oriented model formulation. The relevant land area is divided into cells, and the ignition time of “protection areas” (such as towns, homes, and campgrounds) is delayed as much as possible through spatial application of treatments that have the effect of slowing the fire front movement through each cell. Model variables track the entry and exit times of the fire front and account for the earliest ignition source for each cell. A stylized case example is used to demonstrate the model's application and spatial sensitivity with easily interpretable results. The results show that a spatial concentration of fire management effort may not be optimal, at least for the simple example analyzed. Extension of the model formulation to long-term fuels management is also discussed. FOR. SCI. 46(3): 442–451.

Trigonometric Variable-Form Taper Equations for Australian Eucalypts - Huiquan Bi (Forest Science, 2000)
This article introduces a new variable-form taper model that is stable in specification yet flexible in its ability to fit data for species and trees with different stem forms. The base function is constructed from trigonometric volume-ratio equations following the geometry of a tree stem. The specification for the exponent includes variables for depicting changes in stem form along a stem and variables for taking into account differences in stem form among trees of different sizes. This model is fitted to data from 25 species of Australian eucalypts and is compared with Kozak's taper model to demonstrate its characteristics: stability in specification, flexibility in fitting data for species and trees with varying stem forms and accurate predictions of taper and merchantable height. FOR. SCI. 46(3): 397–409.

Book Reviews: Forest Health and Protection by R.L. Edmonds, J.K. Agee, and R.I. Gara - Terry S. Price (Forest Science, 2000)

Upcoming Reviews (Forest Science, 2000)

Analytical Site Index Solution for the Generalized Log-Logistic Height Equation - C.J. Cieszewski (Forest Science, 2000)
The generalized log-logistic height equation computes height as a function of age and a fixed base-age site index. This equation and its modifications have been used for many applications in various regions. It is seemingly apparent that this equation is analytically insolvable for the site index; no general analytical solution to this equation is readily available. This article presents such a solution that has proven to be valid and useful with all tested parameters. This solution is based on an adaptation of the Ramanujan's (1887-1920) solution for a trinomial with real-number exponents. Ramanujan's solution is a series that in many cases can be expressed as a closed-form equation. In the present context, this series may be used for derivations of various special cases of closed-form solutions, initial-condition difference and differential equations, and for various analytical sensitivity and trend analysis, as well as for efficient site index computations. For. Sci. 46(2):291-296

Predicting Daily Mean Soil Temperature from Daily Mean Air Temperature in Four Northern Hardwood Forest Stands - Shannon E. Brown; Kurt S. Pregitzer; David D. Reed; Andrew J. Burton (Forest Science, 2000)
Soil temperature is very important in regulating ecosystem processes, yet it is often difficult and costly to measure. Most models that have endeavored to predict soil temperature have either a long time step or several complicated independent variables. Daily mean air and soil temperatures were measured from 1989-1997 in four northern hardwood sites along a 500 km latitudinal gradient in Michigan. These data were used to derive a simple method to predict daily mean soil temperature (depth of 15 cm) using the daily mean air temperature from the previous day and a cosine function of Julian date (R² = 0.93-0.96; SEM = 0.98-1.40°C). Predicted values were compared with actual recorded soil temperatures from 1997 at each of the sites, and the average difference between the observed and predicted values ranged from 0.11 to 0.39°C. Different coefficients were estimated for each of the sites; however, this general method of predicting soil temperature appears applicable to any site. Once calibrated for a given site, soil temperature may be simply estimated, thus reducing the need for extended monitoring efforts. This method also allows the reconstruction of soil temperature records beyond the monitoring period. Projecting long-term trends in soil temperature may help to further elucidate several ecosystem processes and also may provide more information on how a changing global climate will impact forest ecosystems. For. Sci. 46(2):297-301.

A Theory of Red Pine ( Pinus koraiensis ) Management for Both Timber and Commercial Seeds - Chuan-Zhong Li; KarI-Gustaf Löfgren (Forest Science, 2000)
Red pine (Pinus koraiensis), is a commonly distributed species of tree in northeastern China. The wood is used for manufacturing purposes as usual, and the seeds are used as a source of delicious food and for medical applications. If the top of the tree is removed at a mature age, seed production is much enhanced. In this article, we derive optimal harvesting rules for such multiple use management of red pine trees. We give optimality conditions for cutting off the top of the tree, the intensity of removal, and the optimal date for the final felling. The two harvesting dates will indirectly determine the optimal length of commercial seed production. We also derive comparative static results on how the rotation periods and the intensity of removal changes, as a function of prices and the interest rate. The theory is also applicable to the economic management of seed orchards, where the practice of cutting off the top of the tree is used, all over the world, to induce seed production. For. Sci. 46(2):284-290.

Effects of Correlation among Parameters on Prediction Quality of a Process-Based Forest Growth Model - Biing T. Guan (Forest Science, 2000)
A nonparametric method was introduced as a technique for evaluating the effects of parameter correlation on prediction quality of process-based forest growth models. The method was based on a rank correlation and Cholesky decomposition. For a given data matrix, by reordering the observations, the method would produce a rearranged matrix with the desired correlation structure. The method was computationally simple and efficient. Using a process-based model calibrated for red pine (Pinus resinosa Ait.) as an example, small-scale Monte Carlo simulations revealed that parameter correlation had different effects on the model's prediction means and variances, depending on the importance of the parameters involved. In general, given the same level of correlation, correlation between two important parameters would have greater influences on prediction quality than correlation between two less important parameters. Parameter correlation slightly affected the prediction means but could significantly change prediction variances. The relationship between prediction quality and the degrees of correlation, however, was not necessarily a linear one. The same parameter correlation might also have different effects on different state variables. For. Sci. 46(2):269-276.

Tree-Growth and Understory Responses to Low-Severity Prescribed Burning in Thinned Pinus ponderosa Forests of Central Oregon - Matt D. Busse; Steven A. Simon; Gregg M. Riegel (Forest Science, 2000)
The growth of ponderosa pine and associated understory vegetation was evaluated for a 6 yr period following spring underburning of surface fuels. Underburn and control (unburned) plots were paired at 15 replicate sites in pole-sized ponderosa pine forests of central Oregon. The burns were generally low in severity, as noted by low 0 horizon mass reduction (24%) and tree mortality (6%). A small but significant decline in basal area and volume growth rates of surviving trees was found in the 6 yr following underburning. The reduction in tree growth was related to a combination of crown length reduction, 0 horizon reduction, and site productivity. More productive stands had the highest proportional reduction in growth due to burning. By comparison, site conditions including stand density, initial basal area, elevation, parent material, and soil fertility were not related to the observed growth reduction. Understory vegetation showed a mixed response to burning. Shrub cover, dominated by Purshia tridentata, declined significantly following burning and remained well below preburn levels for the length of the study, even though one-fourth of all burned Purshia plants successfully resprouted. Total herbaceous vegetation cover and production were unaffected by burning, while species diversity increased slightly. With the exception of the decline in Purshia cover, the results indicate that low-severity prescribed burning has a relatively minor impact on tree-growth and understory response in thinned ponderosa pine stands. For. Sci. 46(2):258-268.

Asymmetric Day/Night Temperature Elevation: Growth Implications for Yellow-Poplar and Loblolly Pine Using Simulation Modeling - John V.H. Constable; William A. Retzlaff (Forest Science, 2000)
Using the TREGRO simulation model we examined the relative impact of asymmetric and symmetric elevations of day/night temperatures on 3 yr biomass gain of yellow-poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.). Temperature elevation scenarios used were: (1) an asymmetric 0.3°C/0.9°C increase in day/night temperature (T + 0.3/0.9) as observed since the turn of the century; (2) a symmetric 4°C elevation during both day and night periods (T + 4) as predicted by general circulation models; and (3) an asymmetric 2°C/6°C elevation of day/night temperature (T + 2/6). TREGRO incorporates temperature effects on photosynthesis, respiration, growth rate, and phenology. In both species for all temperature elevation scenarios, respiratory increases exceeded photosynthetic increases and reduced belowground growth. In yellow-poplar, belowground growth was reduced by 7.6% in the T + 0.3/0.9 scenario, whereas the T + 4 and T + 2/6 scenarios reduced belowground growth by 145% and 155%, respectively. The elevated temperature scenarios increased total tree biomass of loblolly pine, but belowground growth was reduced by 24%, 111%, and 113% by the T + 0.3/0.9, T + 4, and T + 2/6 scenarios, respectively. Reductions in root biomass at elevated temperatures may influence competitive interactions between forest tree species and susceptibility to environmental fluctuations. For. Sci. 46(2):248-257.

A Model and Tabu Search Method to Optimize Stand Harvest and Road Construction Schedules - Evelyn W. Richards; Eldon A. Gunn (Forest Science, 2000)
An important function of tactical planning in forest management is to choose spatially and temporally explicit schedules for both harvesting and road construction activities. In addition to maintaining consistency with goals of the strategic planning process, harvesting decisions are subjected to spatial, environmental constraints. At the same time, planning and cost of road access over the medium-term planning horizon must be considered.This article presents a model and heuristic solution methodology to address stand level harvest scheduling and the associated road construction scheduling problem. The model is formulated to determine minimal cost schedules, for stand harvests and road construction, that achieve recommended timber harvest volume targets and that comply with environmental regulations. The harvest decisions are made at the stand level of resolution. Graph structures are used to formulate the spatial restrictions on clearcut opening size and location. Road construction projects are scheduled to create a feasible road network at minimum net present capital cost.The optimization problem is solved using a Tabu search heuristic, which includes special constructs to cope with the complexity of this problem. An efficient frontier of solutions is produced, which may be utilized to analyze tradeoffs between lost forest productivity, due to timing of harvests, and the capital cost of road construction. Forest Science 46(2):188-203.

Optimizing Forest Stand Management with Natural Regeneration and Single-Tree Choice Variables - John Hof; Michael Bevers (Forest Science, 2000)
This article addresses the any-aged forest management problem with individual trees as the choice variables in integer programming models. In order to sustain the forest using natural regeneration, spatial proximity of seed trees is required for harvesting to take place in these models. This problem requires integer variables to avoid harvesting part of a tree, but it is remarkably integer-friendly. Solvability of large models is thus explored, along with the patterns of solution that can be recognized in smaller models. Results from these exploratory models are sensitive to initial forest conditions and do not display the steady state conditions typically assumed for uneven-aged management in the literature. For. Sci. 46(2):168-175.

Impacts of the Time Horizon for Adjacency Constraints in Harvest Scheduling - Howard M. Hoganson; Jose G. Borges (Forest Science, 2000)
Adjacency constraints, constraints which limit the harvest timings of adjacent management units, are a challenge to address within forest management scheduling models. Four large test cases were examined to consider the need to recognize site-specific adjacency constraints over a long time horizon within a forest management scheduling model. Results suggest that the costs of adjacency constraints tend to be short-term in nature. Immediate periods tend to be influenced most because there is less lead time to prepare for the constraints. Little may be gained in planning by addressing adjacency constraints for more than a full rotation length. Adjacency constraints can likely be satisfied efficiently without having large shifts in harvest timings for most all management units. Results are consistent with an interpretation of the dual formulation of a relaxed linear programming formulation of the problem. For. Sci. 46(2):176-187.

Understanding the Tradeoffs Between Site Quality and Species Presence in Reserve Site Selection - Richard Church; Ross Gerrard; Allan Hollander; David Stoms (Forest Science, 2000)
A number of optimization models have been developed for natural reserve design and reserve site selection. The most common approach seeks to maximize the number of individual species that occur among chosen sites. A number of heuristics and mathematical programming algorithms have been applied to solve this problem. Although attaining maximum overall species representation is important, the relative quality of representation [which could be affected by site attributes such as habitat value, adequate population size, presence of critical resources, existence (or lack thereof) of exotic competitors, etc.] has been absent from most representation models. Yet issues of site quality should be considered in order to have any assurance of long-term species persistence in a reserve system. Here we present a multiobjective optimization model that addresses the issue of balancing species presence with habitat quality. One type of interesting alternative yields more high quality representation at the price of some reduction in overall representation. We present an application using a large dataset from California Gap Analysis to demonstrate this and other tradeoffs. Optimal solutions are attained using commercial integer programming software with very reasonable computational effort. For. Sci. 46(2):157-167.

Spatial Modeling in Forest Management and Natural Resource Planning - Alan T. Murray; Stephanie Snyder (Forest Science, 2000)

Front Matter Volume 46 Issue 2 2000 (Forest Science, 2000)

Book Reviews: Forest Plants of the Southeast and Their Wildlife Uses - Timothy B. Harrington (Forest Science, 2000)

Fostering the Production of Nontimber Services Among Forest Owners with Heterogeneous Objectives - Jeffrey D. Kline; Ralph J. Alig; Rebecca L. Johnson (Forest Science, 2000)
Programs to enhance nontimber services increasingly focus on nonindustrial private forest (NIPF) owners. These owners are believed to possess multiple objectives, causing them to respond to economic forces and policies in complex and unpredictable ways. We examine NIPF owners in western Oregon and western Washington, using a survey to document their forest ownership objectives and willingness to accept incentive payments to forego harvesting to improve wildlife habitat. An empirical model is developed describing owners' willingness to accept incentive payments to delay harvest, as a function of their forest ownership objectives and socioeconomic characteristics. Mean incentive payments necessary to induce owners to forego harvest are higher for owners possessing primarily timber objectives ($301-314/ha/yr), than for owners possessing both timber and nontimber objectives ($254-257/ha/yr) or primarily recreation objectives ($185-210/ha/yr). An estimated supply curve describing the area of NIPF land on which owners would forego harvesting for 10 yr varies from relatively flat to fairly steep. Although many owners would require little or no incentive to forego harvest, others would require a significant incentive. Nontimber services likely could be enhanced by targeting incentive programs or technical assistance toward NIPF owners possessing nontimber objectives. For. Sci. 46(2):302-311.

Using Numerical Optimization for Specifying Individual-Tree Competition Models - Jari Miina; Timo Pukkala (Forest Science, 2000)
In this article we present a method that combines maximum likelihood estimation and nonlinear programming in growth modeling. The method of Hooke and Jeeves is used to discover the optimal specification of a particular competition index type, while statistical software is used to fit the regression model with the given competition index type. The log-likelihood computed by the statistical software is fed back to the optimization algorithm, which alters the specification of the competition index type based on the changes in the log-likelihood. This approach was tested for a mixture of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.). The characteristics of five different competition index types were optimized. The best model included an index computed from vertical angles formed by a horizontal plane and the tops of competitors. The elevation of the horizontal plane was computed with a species-specific linear regression model using height of the subject tree as the predictor. Pine competitors nearer than 6 m and spruce competitors nearer than 9--10 m were included in the optimal competition index. This study showed that the approach used here is highly efficient. For. Sci. 46(2):277-283.

Validation of a Forest Values Typology for Use in National Forest Planning - Gregory Brown; Patrick Reed (Forest Science, 2000)
Public values for national forestlands are assumed to underlie preferences for actual forest use and define the context for forest planning and decision making, but the relationship between preferences and attitudes toward forest management activities and public forest values (both use and nonuse values) is not well understood. Using data from a survey of Alaskan residents in the Chugach National Forest plan revision process, the relationship between attitudes toward forest management actions and forest values is examined using a variety of statistical procedures. Key findings indicate that: (1) survey respondents were able to identify with 13 distinct forest values based on a modified forest value typology developed by Rolston and Coufal (1991), (2) no obvious latent structure of variables or constructs emerged from factor analysis of the 13 forest values indicating that the forest value typology may not be easily simplified without compromising the exclusiveness of measured forest values, (3) small, but statistically significant correlations were found between attitudes toward specific forest management practices such as logging and mining and held forest values, and (4) forest values are modestly predictive of respondent preferences for specific forest planning decisions. For. Sci. 46(2):240-247.

Modeling Tree-Ring Growth Responses to Climatic Variables Using Artificial Neural Networks - Qi-Bin Zhang; Richard J. Hebda; Qi-Jun Zhang; René I. Alfaro (Forest Science, 2000)
Modeling the nonlinear and complex relationships between climate and tree-ring growth is of significance in dendroclimatic studies, but difficult to implement using traditional linear regression approaches. To overcome this difficulty, the technique of Artificial Neural Network (ANN) was employed in this study to develop the growth response models using the climate/growth database for Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) on southern Vancouver Island, Canada. The results show that the ANN models are able to extract nonlinear growth response patterns from the observed climate/tree-ring datasets, and to generate more accurate predictions than multiple linear regression approaches. The ANN-extracted climate-growth relationships can be displayed by scenario analysis; for example, when all other input variables are held fixed at their means, the limiting effect of April-July precipitation on tree growth decreases with increased precipitation. The main difficulty of applying ANN technique in dendroclimatology is the problem of overlearning (i.e., the ANN learns too many specific climate-growth patterns and loses the ability to generalize between similar climate-growth patterns). This problem can be alleviated by carefully designing the ANN, such as reducing the number of input variables, choosing a variety of training/testing sets, designing partially connected architectures with a small number of neurons in the hidden layer, and using early stopping during training process. The reliability of the derived ANN models is assessed by validation on independent testing datasets. The main advantages of the ANN technique over traditional dendroclimatic approaches are its ability to capture nonlinear climate-growth response, and its nonreliance on preassumed functional relationships for describing the observed datasets. The ANN method introduced in this article is sufficiently general to be applicable to many forest ecological modeling applications. For. Sci. 46(2):229-239.

Neutrality of Forestry Income Taxation and Inheritable Tax Exemptions for Timber Capital - Jussi Uusivuori (Forest Science, 2000)
This article examines the neutrality of income taxation in the so-called Austrian sector of the economy. By focusing on the forestry sector, it is shown that certain exemption practices of yield taxation can be modified to restore the efficiency of the taxation. Earlier research on the production efficiency relating to different capital income tax systems in the Austrian sector shows that yield taxes based on realized income lead to inefficient allocation of resources between the Austrian and the ordinary sector of the economy when pretax distortions are present. The models used in the earlier tax literature do not, however, differentiate between taxing capital income and taxing the initial capital under an individual occupancy of an asset. In this article, by explicitly separating timber capital taxation from timber capital income taxation, a modified yield taxation scheme is presented, which gradually corrects an initially distorted allocation of resources between forests and other assets in the economy. For. Sci. 46(2):219-228.

A Three-Stage Heuristic for Harvest Scheduling with Access Road Network Development - Mark M. Clark; Russell D. Meller; Timothy P. McDonald (Forest Science, 2000)
In this article we present a new model for the scheduling of forest harvesting with spatial and temporal constraints. Our approach is unique in that we incorporate access road network development into the harvest scheduling selection process. Due to the difficulty of solving the problem optimally, we develop a heuristic that consists of a solution construction stage and two solution improvement stages. We call our approach INROADS and compare it to three other approaches by employing hypothetical example problems with 225 stands (or cut blocks) over a three-period planning horizon. Thirteen example forests that vary in terms of stand value and spatial dispersion are used to evaluate our heuristic, which outperforms the other approaches tested. For. Sci: 46(2):204-218.

Back Matter Volume 46 Issue 2 2000 (Forest Science, 2000)

Upcoming Reviews (Forest Science, 2000)

Tree Biotechnology: Towards the Millennium - Scott A. Merkle (Forest Science, 2000)

Maintaining Biodiversity in Forest Ecosystems - Andrew B. Carey (Forest Science, 2000)

Relative Abundance and Species Richness of Herpetofauna in Forest Stands in Pennsylvania - Brad Ross; Todd Fredericksen; Eric Ross; Wayne Hoffman; Michael L. Morrison; Jan Beyea; Michael B. Lester; Bradley N. Johnson; Nell J. Fredericksen (Forest Science, 2000)
The relative abundance and species richness of herpetofauna was investigated to assess the impact of recent logging operations in 47 forest stands in northeastern Pennsylvania during 1996 and 1997. Stands including nonindustrial private forestlands and public lands that have received some type of harvesting within the last 8 yr ranged from near complete overstory tree cover to complete removal of overstory cover. Stands included the two dominant forest types in the region: northern hardwood (Betula, Fagus, Prunus, Acer, and Tsuga spp.) and oak-hickory/(Quercus and Carya spp.). A total of 8,181 individuals of 26 species (12 salamander, 7 snake, 6 frog, and 1 toad species) were observed in the study stands. The relative abundance and species richness of salamanders increased significantly with increasing retention of tree basal area. Forest stands containing > 15 m²/ha live tree basal area appeared to be a threshold level for high salamander abundance. Snake species abundance and richness increased significantly with increasing removal of tree basal area. The abundance of anuran species showed no significant relationship with amount of tree basal area removal, but the relative abundance and species richness of anurans depended on the presence of water within or bordering the stands. Forest type did not change the overall response of herpetofauna community composition to forest harvesting, although salamanders were more abundant in northern hardwood stands, and snakes were more abundant in oak-hickory stands. Patterns and threshold levels of abundance and species richness of herpetofauna determined in this study may be used to maintain the abundance and richness of selected species when harvesting forest stands. For. Sci. 46(1):139-146.

Prediction of Annual Diameter Growth and Survival for Individual Trees from Periodic Measurements - Quang V. Cao (Forest Science, 2000)
It is difficult to fit annual tree survival and diameter growth models to data that were measured, not every year, but at some interval. This study aimed to determine suitable methods to obtain parameter estimates for such a system from periodic measurements. Given a system consisting of a tree survival model and a tree diameter growth model, this article presents an iterative method for estimating system parameters. The method involves sequentially updating of the parameters of both models within the growth period. Data from 111 plots from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) were then used to evaluate this iterative approach against the averaging method that assumes a constant tree survival probability and diameter growth rate during the remeasurement interval. Results indicated that the iterative method out-performed the averaging method in predicting future individual tree survival, diameter growth, and stand basal area. The iterative method was superior because it accounted for the variable rate of diameter growth and tree survival probability as functions of ever-changing stand and tree attributes. For. Sci. 46(1):127-131.

Duality and Faustmann: Implications for the Evaluation of Landowner Behavior - Richard J. Brazee; Gregory S. Amacher (Forest Science, 2000)
This paper examines the behavioral consequences when landowners seek to minimize costs rather than maximize profits. We derive a cost function that is dual to the net present value function in the Faustmann Model. This cost function provides a theoretical foundation for studies that estimate forest production costs. We use comparative statics methodology to derive qualitative results for changes in selected policies and exogenous parameters. We find that the qualitative impacts under cost minimization are usually unambiguous. Qualitative impacts under profit maximization are usually ambiguous. This implies that behavioral impacts are usually easier to assess a priori, when landowners minimize costs rather than maximize profits. For. Sci. 46(1):132-138.

Front Matter Volume 46 Issue 1 2000 (Forest Science, 2000)

Logistic Regression for Southern Pine Beetle Outbreaks with Spatial and Temporal Autocorrelation - Marcia L. Gumpertz; Chi-tsung Wu; John M. Pye (Forest Science, 2000)
Regional outbreaks of southern pine beetle (Dendroctonus frontalis Zimm.) show marked spatial and temporal patterns. While these patterns are of interest in themselves, we focus on statistical methods for estimating the effects of underlying environmental factors in the presence of spatial and temporal autocorrelation. The most comprehensive available information on outbreaks consists of binary data, specifically, annual presence or absence of outbreak for individual counties within the southern United States. We demonstrate a method for modeling spatially correlated proportions, such as the proportion of years that a county experiences outbreak, based on annual outbreak presence or absence data for counties in three states (NC, SC, and GA) over 31 yr. In this method, the proportion of years in outbreak is predicted using a marginal logistic regression model with spatial autocorrelation among counties, with adjustment of variance terms to account for temporal autocorrelation. This type of model describes the probability of outbreak as a function of explanatory variables such as host availability, physiography, climate, hurricane incidence, and management type. Explicitly including spatial autocorrelation in the model improves estimates of the probability of outbreak for a particular county and of the importance of the various explanatory variables. For. Sci. 46(1):95-107.

A Timber Extraction Method Based On Pavement Serviceability and Forest Inventory Data - Audrey Martin; Philip Owende; Shane Ward; Micheal O'Mahony (Forest Science, 2000)
A methodology for integrating pavement classification and forest inventory data to determine the capability of forest access roads with weak subgrades to support timber extraction is described. GPS location data recorded in stand-alone mode was superimposed on forest and Ordnance Survey maps. Within a GIS, the acquired spatial data was manipulated and integrated with pavement attribute information and the current and projected forest inventory data. Potential pavement damage by a typical timber haulage truck with payloads of 22, 27, 30, and 35 tonnes (t) was then assessed. It was found that by overloading the truck by 3 and 8 t (GVW of 43 t and 48 t, respectively), the total volume of timber that could be conveyed without damaging the serviceable pavements reduced by an average of 16 and 44%, respectively. Rerouting of timber to avoid critical and failed sections could significantly increase the transportation costs. Rerouting was found to be impractical where forest compartments were accessible by single routes; hence, necessary repairs to facilitate the extraction are recommended in such cases. The final database could be extended to include specific costing of repair and maintenance requirements, and so determine the economic implications of respective routing strategies. For. Sci. 46(1):76-85.

Analytical Group Decision Making in Natural Resources: Methodology and Application - Daniel L. Schmoldt; David L. Peterson (Forest Science, 2000)
Group decision making is becoming increasingly important in natural resource management and associated scientific applications, because multiple values are treated coincidentally in time and space, multiple resource specialists are needed, and multiple stakeholders must be included in the decision process. Decades of social science research on decision making in groups have provided insights into the impediments to effective group processes and on techniques that can be applied in a group context. Nevertheless, little integration and few applications of these results have occurred in resource management decision processes, where formal groups are integral, either directly or indirectly. A group decision-making methodology is introduced as an effective approach for temporary, formal groups (e.g., workshops). It combines the following three components: (1) brainstorming to generate ideas; (2) the analytic hierarchy process to produce judgments, manage conflict, enable consensus, and plan for implementation; and (3) a discussion template (straw document). Resulting numerical assessments of alternative decision priorities can be analyzed statistically to indicate where group member agreement occurs and where priority values are significantly different. An application of this group process to fire research program development in a workshop setting indicates that the process helps focus group deliberations; mitigates groupthink, nondecision, and social loafing pitfalls; encourages individual interaction; identifies irrational judgments; and provides a large amount of useful quantitative information about group preferences. This approach can help facilitate scientific assessments and other decision-making processes in resource management. For. Sci. 46(1):62-75.

Valuing a Forest as a Call Option: The Sale of Forestry Corporation of New Zealand - Warren R. Hughes (Forest Science, 2000)
In September 1996, the New Zealand (NZ) Government sold its 100% shareholding in the Forestry Corporation of NZ (FC) to a consortium led by Fletcher Challenge Forests (FF), a publicly listed company, for NZ $2.06 billion. Option pricing methodology is used to value the forest assets that were listed in FC's 1996 Annual Report at $1.853 billion. Total net assets had a book value of $2.03 billion, about $30 million less than the selling price. Assuming a 7.5% real cost of capital and a maximum tax rate of 33%, the actual value of the forest assets realized in the sale (taken to be $1.853 billion) are at a 12.9% discount to the "fair" value of $2.128 billion derived by the option pricing approach. The advantage of this approach to forest valuation over the traditional approach (based on discounted cash flow using projected future prices over long horizons) is that only the volatility of future log prices need be estimated. The relative insensitivity of forest value to this parameter suggests less spread between bid and ask prices by forest buyers and sellers with similar costs of capital, tax rates, and so on. For. Sci. 46(1):32-39.

Optimal Harvesting and Thinning with Stochastic Prices - Richard J. Brazee; Erwin Bulte (Forest Science, 2000)
This article rigorously incorporates optimal thinning decisions for an even-age stand into an optimal harvesting model with fluctuating stumpage prices. The theoretical model optimally determines how often and at what ages to thin when stumpage prices are independently drawn from a stationary distribution. New theoretical results include increases in the net present value of both land and stumpage, and an increase in some harvest reservation prices from introducing thinning. A simplified model is numerically simulated using parameters estimated from Dutch data for Pinus sylvestris to determine when to thin. The simulation results suggest that the gains from incorporating thinning are significant when compared to the Faustmann approach and at least modestly important when compared to optimal harvesting models without thinning. The simulation results also indicate that expected thinning age may decrease significantly while the expected harvest age increases, when compared to the Faustmann approach. For. Sci. 46(1):23-31.

Dynamics of Coarse Woody Debris Placed in Three Oregon Streams - Richard F. Keim; Arne E. Skaugset; Douglas S. Bateman (Forest Science, 2000)
Many streams of the North American west coast are deficient in coarse woody debris (CWD) and have been subjected to aquatic habitat restoration by adding CWD. The ready availability of alder (Alnus rubra Bong.) CWD makes it attractive for such uses, but the dynamics of this relatively small debris are poorly understood. We placed CWD in three third-order streams in western Oregon either as large, key pieces (pulled-over streamside alders or bucked conifer logs) or as smaller logging debris (mostly alder). This treatment immediately increased CWD in the streams by 86% to 155%. We used chronosequences of surveys to evaluate whether the increased loadings of CWD persisted for more than a year, and whether the key pieces trapped smaller debris to create accumulations. Although there was more CWD in all three streams during the 3 yr after treatment than there had been before treatment, rates of movement were high. Aggregation of CWD increased in all three streams for at least 1 yr, and accumulations of CWD associated with key pieces were larger after 3 yr than immediately after treatment. Pulled-over alders were more stable and more effective in forming accumulations than bucked conifers but were subject to rapid decay. For. Sci. 46(1):13-22.

Editor's Annual Report - Robert G. Haight (Forest Science, 2000)

Brief Notices (Forest Science, 2000)

Errata (Forest Science, 2000)

Generalized Algebraic Difference Approach: Theory Based Derivation of Dynamic Site Equations with Polymorphism and Variable Asymptotes - C.J. Cieszewski; R.L. Bailey (Forest Science, 2000)
Biologically realistic site models require the ability to concurrently express variable asymptotes and polymorphism in curve shapes. Moreover, it is only logical and rational to require that these models be invariant to changes in the index or base age. This manuscript explains the Generalized Algebraic Difference Approach that can be used effectively to derive truly base-age invariant difference equations capable of describing concurrent polymorphism and variable asymptotes. This new generic methodology for derivation of even the most complex dynamic equations is mathematically sound. The equations derived with it can be extremely flexible and may generate intricate patterns of concurrent polymorphism and variable asymptotes. This methodology is relevant to all situations in which the dependent variable is a function of an unobservable variable, and the models can be implicitly defined by their initial conditions. It is equally useful for derivation of new equations and for improvement of existing base-age specific equations. For. Sci. 46(1):116-126.

Guided Transect Sampling for Assessing Sparse Populations - Göran Ståhl; Anna Ringvall; Tomas Lämås (Forest Science, 2000)
Guided Transect Sampling is suggested for transect based surveys when sampling sparse and geographically scattered populations. It is a two-stage design in which wide strips are selected in the first stage followed by a subsampling procedure guided by prior information in the second stage. As a basis for the second stage, the target area is divided into grid-cells containing covariate data obtained, for example, by remote sensing. The general principle can be coupled with different transect based survey methods such as strip sampling or line transect sampling. Also, different strategies for the second stage guidance can be used, resulting in estimators with different properties. In this study, Guided Transect Sampling was compared with a traditional strip survey under different simulated forest conditions. The comparisons indicated that the proposed method can improve the efficiency of transect based inventories of sparse populations. For. Sci. 46(1):108-115.

Back Matter Volume 46 Issue 1 2000 (Forest Science, 2000)

Influence of Vertical Foliage Structure on the Distribution of Stem Cross-Sectional Area Increment in Western Hemlock and Balsam Fir - John A. Kershaw; Douglas A. Maguire (Forest Science, 2000)
A set of western hemlock (Tsuga heterophylla Raf. [Sarg.]) and balsam fir (Abies balsamea [L.] Mill.) from western Washington, USA and western Newfoundland, Canada, respectively, were destructively sampled to examine relationships between vertical foliage structure and distribution of stem cross-sectional area increment. A series of stem growth distribution models describing the relationship between amount of foliage area above a given height and stem cross-sectional area increment at that height was derived from the pipe model theory. These models were derived with increasing generality so that two commonly held assumptions could be explicitly tested: (1) linear increase in cross-sectional area increment with increasing foliage area; and (2) constant cross-sectional area increment below base of the live crown. Overall, the models performed very well, accounting for over 80% of the observed variation in cross-sectional area increment for both species. The results show that, while cross-sectional area increment increases with increasing current foliage, the increase is not proportional (i.e., linear). Furthermore, the rate of cross-sectional area increment below base of the live crown was found to increase in the smaller balsam fir trees and decrease in the larger western hemlock trees. These results suggest that cross-sectional area increment per unit foliage below the live crown may change as trees grow. For. Sci. 46(1):86-94.

Effects of an Intense Wildfire in a Mexican Oak-Pine Forest - Peter Z. Fulé; Abel García-Arévalo; W. Wallace Covington (Forest Science, 2000)
An oak-pine forest burned by intense wildfire in April, 1996, and a companion unburned area were sampled 1 month and 1 yr postfire in La Michilía Biosphere Reserve, Durango, Mexico. Up to 90% of the trees were killed or top-killed in the burned area, but larger trees tended to survive, so basal area was only reduced by 66%. Top-killing was relatively higher among fire-susceptible oaks and lower among fire-resistant pines. However, oaks were strong resprouters both in the canopy and at the base of top-killed trees. Damage codes based on crown scorch and bole char were highly accurate when predicting that a tree would die but substantially overestimated survivors. Most tree regeneration was top-killed in the fire, but oak sprout density was 700% that of the unburned area by 1 yr postfire. Manzanita shrubs also resprouted vigorously. Herbaceous production and cover were lower after the first postfire growing season in the burned area than the unburned area. Woody fuels and forest floor depth were also reduced. Although short-term fire effects indicate that the forest ecosystem has moved closer toward a savanna condition, remnant seed trees and sprouting trees are expected to maintain forest cover. Future herbaceous production is likely to increase in response to overstory mortality. Quantification of fire effects is helpful for supporting short-term management decisions since oak-pine forests cover millions of hectares in northern Mexico. As a long-term management strategy, however, we suggest that restoring the frequent, low-intensity fire regime may be desirable for ecological and economic reasons. For. Sci. 46(1):52-61.

The Impacts of Deregulation and Privatization on Cost Efficiency in New Zealand's Forest Industry - Donald L. Grebner; Gregory S. Amacher (Forest Science, 2000)
In this paper, we investigate whether deregulation and privatization induced changes in cost efficiency within the New Zealand wood industry. Unlike previous work, the effects of privatization, deregulation, and removal of log export bans are compared to determine which shock had the most influence on efficiency changes. Cost efficiency is measured by estimating stochastic frontier models using the recent cost function approach, which does not suffer from the endogeneity problems associated with stochastic frontier production function estimation. The results show that cost efficiency decreased after each policy reform, but deregulation was more important in this regard than privatization. This suggests that countries with comparative advantages in wood processing, who also implement deregulation or privatization, may suffer through a short-run period of lower efficiency as the economy adjusts to higher input costs in those sectors. In New Zealand's case, the adjustments most likely affecting efficiency have been investments in new technologies, where time is required to attain maximum efficiency. The results are contrary to other studies that have predicted increased efficiency as a result of privatization. For. Sci. 46(1):40-51.

Compatible Volume-Taper Models for Loblolly and Slash Pine Based on a System with Segmented-Stem Form Factors - Zixing Fang; Bruce E. Borders; Robert L. Bailey (Forest Science, 2000)
By integrating a variable-form differential equation for taper, a segmented-stem system of models involving a taper equation, merchantable volume equation, and total stem volume equation results. Through the constraints imposed on the coefficients of integration, the taper model is continuous at the inflection points, and all components in the system are compatible with each other. Models are derived for a bole with two inflection points, but the constant form factor model (no inflection point) and one inflection point segmented model can be obtained as special cases by substituting appropriate parameters directly into this more general model. All parameters are shared by the components in this compatible system. Simultaneous parameter estimation techniques are used so that all appropriate information is obtained from the data. Based on stem analysis data for 1,280 loblolly pine (Pinus taeda L.) trees and 871 slash pine (Pinus elliottii Engelm.) trees, improved predictions result with respect to predicting a stem profile when compared to a constant form factor model. For. Sci. 46(1):1-12.

1999 Contents (Forest Science, 1999)

1999 Subject Index (Forest Science, 1999)

1999 Author Index (Forest Science, 1999)

Meeting Announcements (Forest Science, 1999)

Upcoming Book Reviews (Forest Science, 1999)

Brief Notice (Forest Science, 1999)

Book Reviews: Spatial Optimization for Managed Ecosystems - Kevin Boston (Forest Science, 1999)

Book Reviews: The North American Forests Geography, Ecology and Silviculture - Micheal S. Golden (Forest Science, 1999)

Estimating Type B Genetic Correlations with Unbalanced Data and Heterogeneous Variances for Half-Sib Experiments - Peng-xin Lu; Timothy L. White; Dudley A. Huber (Forest Science, 1999)
A statistical approach is proposed for estimating type B genetic correlations with unbalanced data and heterogeneous variances across environments. First, parental GCA (one-half of the parental breeding value) effects are predicted separately for each environment using best linear unbiased prediction (BLUP). Second, predicted parental GCAs are weighted by their prediction accuracies and Pearson correlation between weighted GCAs in two environments is obtained. Third, type B genetic correlation is calculated by dividing the Pearson correlation with the mean products of prediction accuracies. Advantages of this approach include: (1) fixed effects are removed using best linear unbiased estimation (BLUE) so that they less seriously confound genetic effects when data are unbalanced; (2) heterogeneous variances associated with genetic group means are adjusted for during the process of parental GCA prediction; and (3) it is applicable when experimental designs are different in two environments. Numeric comparisons of estimation methods using simulated data of known true genetic parameters indicated that the new approach produces less bias and higher precision when data are highly unbalanced or have high level heterogeneity of variances across environments. For slightly or moderately unbalanced data, the method of Yamada (1962), however, is simpler and yields satisfactory estimates using standardized data. For. Sci. 45(4):562-572.

A Framework for Forest Accounting - Jeffrey R. Vincent (Forest Science, 1999)
Many recent empirical studies have proposed a variety of forest-related adjustments to the national income accounts. The complexity of forest-economy interactions makes such adjustments prone to double-counting and other problems if they are not guided by economic theory. This paper presents a framework for making internally consistent, theoretically sound adjustments. The framework offers two broad guidelines for applied work. First, one should adjust the overall level of gross domestic product (GDP), and thus net domestic product (NDP), for household consumption of nonmarket forest amenities and nontimber products, but not for production externalities. Accounting for production externalities involves reallocating value added among different production sectors included in GDP. Second, one should adjust NDP for the net accumulation (not just depreciation) of forest-related assets, including the timber stock, the carbon stock, and land converted from forest to other uses. The framework also offers some guidance for methods to quantify values associated with these adjustments. For. Sci. 45(4):552-571.

Testing the Forest Rotation Model: Evidence from Panel Data - Jari Kuuluvainen; Olli Tahvonen (Forest Science, 1999)
The effects on harvesting decisions of intertemporal and parametric changes in prices and forest owners' nonforest income are investigated using panel data. A behavioral timber supply function is derived using a utility-based rotation model, where the forest owner decides an optimal harvesting date for an even-aged stand simultaneously with his optimal life cycle consumption and savings. Capital markets are perfect and forests are valued in situ. The effects of intertemporal changes in the exogenous variables on the annual harvest are estimated using a fixed-effects tobit model and a sample of 119 Finnish farmer-forest owners in 1982-1991. The intertemporal effect on supply of timber price is positive while the effect of nonforest income is negative. The parametric effects of price and income levels on life cycle harvest, as measured by the average annual harvest per hectare over the sample period, are studied by using the estimated fixed effects and the individual sample means of exogenous variables. The parametric effect of the timber price level is negative and that of nonforestry income level positive. These signs are predicted by the utility-based rotation model, provided forests are valued in situ and the average harvest age is lower than that of maximum sustainable yield. For. Sci. 45(4):539-551.

Assessing Uncertainty in a Stand Growth Model by Bayesian Synthesis - Edwin J. Green; David W. MacFarlane; Harry T. Valentine; William E. Strawderman (Forest Science, 1999)
The Bayesian synthesis method (BSYN) was used to bound the uncertainty in projections calculated with PIPESTEM, a mechanistic model of forest growth. The application furnished posterior distributions of (a) the values of the model's parameters, and (b) the values of three of the model's output variables--basal area per unit land area, average tree height, and tree density--at different points in time. Confidence or credible intervals for the output variables were obtained directly from the posterior distributions. The application also provided estimates of correlation among the parameters and output variables. BSYN, which originally was applied to a population dynamics model for bowhead whales (Raftery et al. 1996, JASA 90:402-442), is generally applicable to deterministic models. Extension to two or more linked models is discussed. A simple worked example is included in an appendix. For. Sci. 45(4):528-538.

Forest Stand Structure of the Northern Spotted Owl's Foraging Habitat - Malcolm P. North; Jerry F. Franklin; Andrew B. Carey; Eric D. Forsman; Tom Hamer (Forest Science, 1999)
Although the spotted owl's close association with old growth has been extensively studied, it has been more difficult to identify and quantify the abundance of particular stand structures associated with preferred owl foraging sites. Old-growth forests have a suite of characteristics that distinguish them from younger forests but which also make it difficult to isolate individual structural features important to the spotted owl. This study used an analysis of use-only sites in areas where natural disturbance had created a gradient of old-growth structural characteristics. We used radio telemetry data collected from reproducing owl pairs to locate sample stands and compute a relative measure of owl-use intensity in each stand. Snag volume and tree height class diversity (a measure of canopy layering) were the stand structures significantly associated with owl foraging intensity. Stands with 142 m³/ha of intact snags and a high diversity of tree heights had medium or high foraging use by spotted owls. In these old-growth stands, biological legacies (e.g., large trees and snags) produced by past disturbance provide important forest structures associated with spotted owl foraging use. For. Sci. 45(4):520-527.

Seedling Leaf Structure of New England Maples ( Acer ) in Relation to Light Environment - P. Mark S. Ashton; Hae Soon Yoon; Rajesh Thadani; Graeme P. Berlyn (Forest Science, 1999)
Seedling leaves of the genus Acer from southern New England were compared in relation to light. The species investigated were red maple (A. rubrum L.), a species tolerant of xeric and hydric sites; silver maple (A. saccharinum L.), a species restricted to riparian sites that are periodically flooded; and sugar maple (A. saccharum Marsh.), a mesic species of lower slopes and valleys. Germinating seedlings of all species were collected and grown within four shade treatments that had contrasting light quantity and quality: (1) approximately 100% of full sunlight, red:far-red ratio = 1.27; (2) 40% of full sunlight, ratio = 0.97; (3) 15% of full sunlight, ratio = 0.85; and (4) 4% of full sunlight, ratio = 0.46. Leaves, cuticles, and epidermal and palisade mesophyll cell layers were all thicker, and stomatal densities were higher for all three species in the full sun treatment. Dimensions of leaf structure (leaf thickness, palisade mesophyll thickness, lower epidermal thickness) were between 25 and 35% smaller for silver maple as compared to the other maples. Silver maple also allocated less biomass to roots (about 15% less) and more to stems. Its thin upper surface cuticle, thin leaves, and large leaf area predispose this species to desiccation. Phenotypic plasticity of leaf anatomical measures was greatest for red maple, suggesting it to be more of a generalist than its congeners. Red maple allocated greater biomass to roots in shade (17% and 27% more than sugar and silver maple respectively), with thicker leaves and cuticle, making it least prone to desiccation. Sugar maple had greater dry mass and total leaf area in the deepest shade than the other maples. Measures of leaf structure can provide useful insights into known ecological affinities of site and shade-tolerance among maples. For. Sci. 45(4):512-519.

A New Algorithm for Stand Table Projection Models - Quang V. Cao; V. Clark Baldwin (Forest Science, 1999)
The constrained least squares method is proposed as an algorithm for projecting stand tables through time. This method consists of three steps: (1) predict survival in each diameter class, (2) predict diameter growth, and (3) use the least squares approach to adjust the stand table to satisfy the constraints of future survival, average diameter and stand basal area. The new method was evaluated against the Weibull parameter-recovery approach and another stand table projection method, using data from direct-seeded stands of loblolly pines (Pinus taeda L.). The constrained least squares method provided the best goodness-of-fit statistics (K-S, χ², and an error index) that were significantly different from those produced by the other two methods. This new algorithm can be employed in cases where diameter data do not necessarily follow the Weibull distribution. For. Sci. 45(4):506-511.

Stochastic Representation of Fire Behavior in a Wildland Fire Protection Planning Model for California - J. Keith Gilless; Jeremy S. Fried (Forest Science, 1999)
A fire behavior module was developed for the California Fire Economics Simulator version 2 (CFES2), a stochastic simulation model of initial attack on wildland fire used by the California Department of Forestry and Fire Protection. Fire rate of spread (ROS) and fire dispatch level (FDL) for simulated fires "occurring" on the same day are determined by making coordinated draws from compound distributions characterizing 2 PM fire behavior indices such as ROS, then adjusting these draws using diurnal adjustment coefficients derived from hourly fire weather observations. Statistical examination of historical fire occurrence and predicted behavior data validated CFES2's use of independent fire occurrence and fire behavior modeling processes. For. Sci. 45(4):492-499.

Relating Site Index to Ecological Factors in Black Spruce Stands: Tests of Hypotheses - Jean-François Beaumont; Chhun-Huor Ung; Michè Bernier-Cardou (Forest Science, 1999)
Modeling dominant height through site index, defined as dominant height at some fixed tree age, requires two equations. The site index must be estimated as the average height of dominant trees at base age, and dominant height must be modeled as a function of age and site index, each model having its own error term. This raises a problem when squared errors are minimized to estimate parameters of interest: the estimates are biased and inconsistent because the error terms are correlated with the explanatory variables. Two additional problems are the autocorrelation among error terms and variance heterogeneity within trees. The generalized method of moments (GMM), which simultaneously takes these problems into account, offers a tool to estimate parameters of the site index and dominant height equations consistently and without bias. Allowing parameters of the height growth model to depend on explanatory variables representing ecological region and drainage class provides useful insight into growth patterns, and improves prediction based on these models. A simulation study confirms that the GMM combined with prewhitening of the time series for each tree produces useful estimates of the parameters and valid statistical tests of hypotheses about their value. For. Sci. 45(4):484-491.

Arbitrage-Free Valuation of a Federal Timber Lease - Ellen Burnes; Enrique Thomann; Edward C. Waymire (Forest Science, 1999)
The objective of this paper is to describe a quantitative framework for offering timber harvest bids on federal lands which includes special considerations of the volatility of timber indices and the harvesting costs involved in harvesting timber. The advantage of such an approach is that it provides a precise framework in which various underlying considerations, such as volatility and cost, may be systematically defined, measured, and evaluated. The valuations derived in this paper provide a market standard against which additional value that encompasses social or environmental welfare may be evaluated. We discuss a specific USDA Forest Service timber sale as a case study to illustrate this approach. For. Sci. 45(4):473-483.

Back Matter Volume 45 Issue 4 1999 (Forest Science, 1999)