Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
Biological & Environmental Engineering
Non Technical Summary
The ultimate goal of this project is to improve our understanding about how to reduce nitrogen (N) loads to the nation's lakes, rivers, and, especially, estuaries. Although N from our nation's agricultural lands has substantially negative and persistent impacts on important aquatic ecosystems (e.g., Chesapeake Bay, Gulf of Mexico), roughly 50% of agricultural N sources are returned to the atmosphere through denitrification. Denitrification is the process of converting soluble forms of N into gaseous forms. Areas in the landscape that are prone to soil saturation are especially effective at denitrifying N i.e., denitrification hotspots. These areas can be leveraged to further reduce N-loads to waterways. Climate change is anticipated to have profound effects on precipitation in the northeastern US. These changes may alter the extent and duration of saturated conditions in these hotspots, which will, in-turn, impact how effectively they denitrify agricultural N. Unfortunately, predictions about climate change are largely based on large-scale, global models with coarse resolution (many square kilometers). It is not obvious how these coarse predictions translate to potential changes in small-scale (a few square meters) soil moisture patterns, which strongly influence dentirfication. We propose down-scaling modeled past and future climate scenarios and using this downscaled weather in watershed models to predict changes in soil moisture and temperature and, ultimately, denitrification. The results will provide a glimpse of whether we can expect our future environment to enhance or diminish the ecosystem service of denitrification. The results will also be translated into maps of denitrifying hotspots, both current and future, to help guide management decisions for reducing N loads to streams. For example, these maps can help identify land to be protected by programs like CRP or CREP to enhance its denitrification potential. These outcomes are especially relevant to NY because the state contributes agricultural runoff to important coastal ecosystems that experience chronic N-related problems, e.g., Chesapeake Bay. New York is also a part of the country where substantial changes in precipitation associated have already been documented. Another important outcome of this project is the establishment of a research team that combines recognized strengths unique to addressing this problem: watershed modeling to predict soil moisture patterns (Walter), climate modeling (P. Hess), nitrogen cycling (B. Richards, S. Kaushal, J. Regan), and effective integration of research and extension (L. Geohring, the USDA recognized our lab as a leader of this type of integration). Very recently researchers in Baltimore have manipulated urban streams in ways to promote saturated conditions in the near-stream soils and have shown that this is an effective way to promote denitrification and reduce N-loads in streams bound for the Chesapeake Bay. Similar innovations may be possible for agricultural landscapes by taking advantage of natural denitrification hotspots such as vernal pools, wetlands, and in- and near-stream areas.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Our ultimate goal is to improve our basic understanding of the interactions among climate, hydrology, and biogeochemistry to inform new and more effective water quality protection strategies. Our specific objectives here are: 1) evaluate likely changes in landscape patterns and magnitudes of denitrification potential and 2) develop maps of current and future denitrification hotspots for use in developing agricultural N-management strategies. An additional objective of this project is to accrue sufficient proof-of-concept data to develop a proposal for a USDA, EPA, or NSF grant to carry-out a more comprehensive project that includes scaling up the types of landscape patterns we anticipate in this project to larger watershed or regional scale and developing lab and field experiments to more empirically evaluate potential climate change impacts on N-cycling.
Project Methods
Because it is not obvious how large scale climate model predictions can be meaningfully translated into changes at the scale of denitrification hotspots, this initial study will focus on modeling. Our strategy is to take the weather predictions from large-resolution global climate models and down-scale them to a watershed-scale through a downscaling strategy that maintains stochastic and spatial coherence of weather information. This weather information is then used to run a hydrologic model that predicts how soil moisture and soil temperatures are distributed across the watershed. The hydrologic model output (soil moisture and temperature) will be used to run a denitrification model. We will focus the Salmon Cr. watershed, near Ithaca, because we have measurements of both stream flow and soil moisture with which we can evaluate our hydrological model. The period 1975-2005 will represent recent conditions and 2030-2060 will be simulated as our "future" scenario. We recognize that we are ignoring lots of potentially important and dynamic factors such as nitrogen deposition, carbon quality, etc., which will be incorporated as static values based on literature, but we think this initial investigation is necessary before we add more realistic complexity.