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Grantee Research Project Results

Grantee Research Project Results

Has Atmospheric Nitrogen Deposition in the Northeast Contributed to the Loss of a Nitrogen-Fixing Plant Species? Exploring Mechanisms Underlying Loss of an Ecologically Important Functional Group from Suitable Habitat

EPA Grant Number: F6F11261
Title: Has Atmospheric Nitrogen Deposition in the Northeast Contributed to the Loss of a Nitrogen-Fixing Plant Species? Exploring Mechanisms Underlying Loss of an Ecologically Important Functional Group from Suitable Habitat
Investigators: Skogen, Krissa A.
Institution: University of Connecticut
EPA Project Officer: Manty, Dale
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $110,007
RFA: STAR Graduate Fellowships (2006)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology , Fellowship - Evolutionary Biology



Nitrogen (N) deposition is a byproduct of fossil fuel combustion and is expected to have globally significant effects on biodiversity, especially in N-limited temperate zone forests. Legumes may be particularly sensitive indicators of the impacts of N deposition. My dissertation research seeks to identify mechanisms contributing to recent population declines of the native forest N2-fixing legume, Desmodium cuspidatum (Fabaceae) in New England, where N deposition is high.Specifically, I hypothesize that enhanced competition between legumes with herbs that do not fix N2, both for soil resources and for pollinators, is associated with increased N deposition, and that this competition is likely to cause legume population declines through changes in demographic transitions required for population growth and persistence. My research will determine whether the decline and loss of populations can be explained, at least in part, by the effects of N deposition on individual growth, reproduction, and survivorship.


I will explore the implications of increased N-deposition for the loss of this N2-fixing plant species through a combination of field, greenhouse and demographic modeling approaches emphasizing population-level dynamics (e.g. competitive effects and demographic transitions). I will also use data on the reproductive biology, germination requirements, demography and competitive response of Desmodium cuspidatum to inform quantitative, stochastic demographic models. I hope to determine whether the demography of extant populations and loss of historic populations is consistent with demographic changes likely to be associated with high rates of N deposition over the last 30-40 years. Range-wide genetic analyses will determine whether New England populations declined in the recent past. An integrative approach is necessary to understand and pinpoint mechanisms leading to species loss as many environmental factors interact in natural systems.

Expected Results:

Because resources available for conservation are limited, efforts that benefit a suite of similar species are preferable to those that focus on one. Desmodium cuspidatum is among 110 plant species in need of research in New England. The results of this project will help determine conservation priorities, will guide management for this species, and will influence conservation of other rare and declining legumes, which are also likely to be sensitive to the effects of N deposition (10% of the National Collection of Endangered Plants and 36% of at risk species in the US are legumes).

Supplemental Keywords:

Nitrogen pollution/atmospheric nitrogen deposition, effects of air pollution, species decline, species extinction, competition, pollinators, reproductive biology, germination, demography, demographic modeling, genetic diversity, nitrogen-fixing plant species, legumes, New England, Northeast,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Monitoring/Modeling, Environmental Monitoring, Ecology and Ecosystems, atmospheric nitrogen, biodiversity, forest ecosystem, environmental impact, ecological risk, legumes, ecological models, air quality, atmospheric chemistry, nitrogen

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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