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Grantee Research Project Results

Grantee Research Project Results

Merging Above- and Belowground Processes: Non-Random Tree Species Change and Microbial Community Function

EPA Grant Number: FP917190
Title: Merging Above- and Belowground Processes: Non-Random Tree Species Change and Microbial Community Function
Investigators: Keiser, Ashley D.
Institution: Yale University
EPA Project Officer: Just, Theodore J.
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010)
Research Category: Academic Fellowships , Fellowship - Global Change

Description:

Objective:

Under predictive climate change models, species’ ranges are expected to move poleward in latitude and upward in elevation with warming. There remains significant uncertainty surrounding the response of belowground carbon and nitrogen cycling and storage to climate changes and related species shifts. The IPCC recognizes the importance of linking biogeochemical cycles to changes in climate, yet belowground carbon cycling has largely been treated as a black-box. My research examines how soil microbial community function, examined as carbon and nitrogen fluxes from decomposing leaf litters, will respond as dominant, overstory tree species shift their ranges due to changing climate conditions. The results will yield an improved understanding of the impacts of non-random tree species change on soil microbial communities and, consequently, the biogeochemistry of forested landscapes.

Synopsis:

Under predictive climate change models, species’ ranges are expected to move poleward in latitude and upward in elevation. Understanding the implications of this movement for biogeochemical cycles is necessary to accurately predict global change impacts on forested ecosystems. This research examines how soil microbial community function, examined as carbon and nitrogen fluxes from decomposing leaf litters, will respond as dominant, overstory tree species shift due to changing climate conditions.

Approach:

I plan to investigate litter decomposition patterns and carbon and nitrogen dynamics on four tree species across an elevation gradient: Liriodendron tulipifera (tulip poplar), Acer rubrum (red maple), Betula alleghaniensis (yellow birch), and Picea rubens (red spruce). The four species have been chosen to represent a range in litter chemistry, their dominance at each study site, and their susceptibility to migrate under predicted climate change models. Leaf litter will be collected beneath mature trees during fall senescence. A reciprocal-transplant field experiment with single- and mixed-species litter bags, combined with a complementary, common garden, laboratory microcosm study, will be used to address this question. At each field collection event, soils and litter will undergo multiple analyses ranging from estimates of soil microbial biomass carbon and nitrogen to litter nutrient analysis. These analyses will permit estimation of net carbon and nitrogen dynamics over time.

Expected Results:

This research will advance our understanding of how microbial community function, exhibited through carbon and nitrogen dynamics, will change as dominant, overstory tree species shift due to changing climate conditions. As a species moves up an elevational gradient, previously dominant species may remain dominant or lose abundance. Resulting leaf litter inputs may impact litter decomposition rates, and ecosystem-level biogeochemical cycles. Understanding the implications of non-random species change for biogeochemical cycles will be necessary to accurately predict global change impacts on forested ecosystems. This is critical in creating realistic carbon and nitrogen budgets at local, regional, and global scales.

Potential to Further Environmental/Human Health Protection:

Changes in aboveground biodiversity are likely to impact essential ecosystem processes, such as nutrient cycling, in such a way that future terrestrial and aquatic community structure and function are altered. The southern Appalachian region, my study site, is considered the “water tower” of the Southeast. Changes to nutrient loads upstream could have a sizeable impact on human populations in the region through diminished drinking water quality. This research proposal is an important step in informing land managers of the potential biogeochemical impacts related to non-random tree species change.

Supplemental Keywords:

carbon, nitrogen, non-random species change, decomposition, temperate forest, global climate change,

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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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