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Nitrogen deposition is altering forest dynamics, terrestrial carbon storage, and biodiversity. However, our ability to forecast how different tree species will respond to N deposition, especially key response thresholds, is limited by a lack of synthesis across spatial scales and research approaches. To develop our best understanding of N deposition impact on tree growth and survival, we will integrate plot-­‐ level studies describing plant growth and survival responses to N inputs and plant-­‐ available soil nutrients with a continental scale analysis across a N deposition gradient. Our primary outcome will be estimates of tree response to N deposition with explicit representation of uncertainty and the identification...
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This proposal brings together biologists and geoscientists to evaluate the evolution of stress tolerance and adaptation to extreme environments in plants. Stress tolerance has been studied mainly from a physiological perspective using laboratory and field experiments. In contrast, this project will take a combined environmental and evolutionary perspective using national public databases and a “big data” approach. Thus the proposal will illustrate an application of spatially integrated big datasets for basic research, a synthesis goal of the Powell Center. We will use the geochemical and mineralogical data from the USGS Soil Geochemical Landscapes of the Conterminous United States Project, digital elevation and...
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The impacts of nitrogen (N) deposition on plant diversity loss have been well documented across N deposition gradients in Europe, but much less so in the U.S. Published N fertilizer studies suggest losses will occur in the US, but many of these were done at levels of N input that were higher than modeled and measured N deposition, and higher than presumed N critical loads. The recent availability of modeled N deposition across the U.S. (e.g. using CMAQ) has provided a high‐resolution tool to identify regions where steep N deposition gradients facilitate detection of ecological shifts. A number of plant diversity (richness plus abundance) data sets across the U.S. have explained diversity shifts based on anthropogenic...
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The timing of breeding is constrained in Arctic ecosystems and small temporal differences in when individuals breed can have large effects on fitness. Arctic ecosystems are generally warming more rapidly than other ecosystems which, for migratory species, can cause an imbalance, or mismatch, between when they have evolved to breed versus when it is optimal to breed environmentally. Geese are abundant herbivores summering in tundra ecosystems, and whose presence has important feedbacks on ecosystem processes. Some goose populations have already exhibited signs that spring vegetation phenology is occurring earlier than individuals are able to breed, with a consequent effect on their reproductive fitness. The magnitude...