Christopher Townsend results 26
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Evaluation of coal combustion residuals in cement systemsNARA Subscribed
Greater stem growth, woody allocation, and aboveground biomass in Paleotropical forests than in Neotropical forestsNARA Subscribed
Forest dynamics and tree species composition vary substantially between Paleotropical and Neotropical forests, but these broad biogeographic regions are treated uniformly in many land models. To assess whether these regional differences translate into variation in productivity and carbon (C) storage, we compiled a database of climate, tree stem growth, litterfall, aboveground net primary production (ANPP), and aboveground biom...
Remotely sensed canopy nitrogen correlates with nitrous oxide emissions in a lowland tropical rainforestNARA Subscribed
Tropical forests exhibit significant heterogeneity in plant functional and chemical traits that may contribute to spatial patterns of key soil biogeochemical processes, such as carbon storage and greenhouse gas emissions. Although tropical forests are the largest ecosystem source of nitrous oxide (N 2 O), drivers of spatial patterns within forests are poorly resolved. Here, we show that local variation in canopy foliar N, mapp...
Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short‐term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer‐term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical for...
Denitrification alternates between a source and sink of nitrous oxide in the hypolimnion of a thermally stratified reservoirNARA Subscribed
Nitrogen loading from developed watersheds to aquatic ecosystems can stimulate microbial denitrification, a process that reduces nitrate (NO − 3 ) to dinitrogen (N 2 ) or nitrous oxide (N 2 O), the latter a potent greenhouse gas. While aquatic ecosystems are a globally significant source of N 2 O to the atmosphere, the relationship between denitrification and N 2 O production is not well known. Until recently, this field of re...
The effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cyclingNARA Subscribed
Summary Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surfa...
Ancient differentiation in the single‐island avian radiation of endemic Hispaniolan chat‐tanagers (Aves: Calyptophilus )NARA Subscribed
The simple geographic structure of island systems often makes them tractable for studies of the patterns and processes of biological diversification. The Calyptophilus chat‐tanagers of Hispaniola are of general evolutionary interest because their multiple lineages might have arisen on a single island, of conservation concern because several isolated populations are nearly extinct, and taxonomically ambiguous because they have...
Aim Techniques that predict species potential distributions by combining observed occurrence records with environmental variables show much potential for application across a range of biogeographical analyses. Some of the most promising applications relate to species for which occurrence records are scarce, due to cryptic habits, locally restricted distributions or low sampling effort. However, the minimum sample sizes require...