Quantifying the Role of Floodplain Forests in Reducing River Nitrogen LoadsEPA Grant Number: FP916935
Title: Quantifying the Role of Floodplain Forests in Reducing River Nitrogen Loads
Investigators: Appling, Alison P
Institution: Duke University
EPA Project Officer: Michaud, Jayne
Project Period: August 1, 2008 through August 1, 2011
RFA: STAR Graduate Fellowships (2008) RFA Text | Recipients Lists
Research Category: Academic Fellowships
Excess nitrogen (N) in rivers pollutes drinking water and causes eutrophication of lakes and coastal systems downstream. Floodplains can provide a valuable ecosystem service by removing N from polluted rivers. Although plants may greatly facilitate this reduction, their effects are not well understood for the many glacial till floodplains where extensive subsurface flow networks are the norm. To address this research need I will investigate how plants in hydrologically complex floodplains mediate patterns of N removal.
In this project I will examine the patterns of floodplain plant effects on N removal from river water. Plants may directly take up N from river water and incorporate it into biomass. Also, plants may have large indirect effects by producing organic matter that fuels microbial denitrification (conversion of dissolved NO3- to N2 gas). Direct and indirect vegetation effects vary spatially and temporally as a consequence of disturbance, soil properties, and the hydrologic transport of materials along subsurface flowpaths. I will use three complementary approaches to examine how plants mediate N removal: 1) measurements of plant uptake and denitrification rates in a hydrologically complex floodplain, 2) development and application of a computer simulation model (WREN-BGC) to synthesize existing knowledge and generate hypotheses about N removal patterns, and 3) tests of model-generated hypotheses using field observations.
Floodplain preservation and restoration can be cost-effective strategies for reducing river N loads, but to achieve these reductions reliably we must understand the processes of N removal. This project will advance scientific understanding of 1) direct and indirect plant effects on floodplain N removal, 2) spatial and temporal patterns of these effects, and 3) strategies for scaling estimates of N removal from small patches to entire flowpaths or floodplains. By clarifying patterns of N removal, my work will open doors to new management tools and will further our ability to use floodplains to improve water quality.