Impacts of Woody Debris on Stream Nitrogen DynamicsEPA Grant Number: F6E10289
Title: Impacts of Woody Debris on Stream Nitrogen Dynamics
Investigators: Warren, Dana Richard
Institution: Cornell University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $106,172
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems , Academic Fellowships
Nitrogen (N) deposition occurs broadly across northeastern North America. The amount of N that is exported to coastal estuaries – where it contributes to eutrophication – is dependant upon how much N is retained in the ecosystem (forests and streams). The goal of my research is to evaluate stream N retention and specifically to quantify the influence that wood in streams has on the uptake and retention of nitrate (NO3-). I will conduct mass balance estimates and nutrient releases to quantify retention and uptake velocity respectively in three headwater systems. I will then manipulate the amount of wood and evaluate changes in N dynamics to quantify the influence of wood on these processes. This research has potential application in 1) developing our understanding of aquatic-terrestrial linkages, 2) modeling nutrient export from forested watersheds, and 3) improving stream restoration techniques.
This study has two primary research objectives under the broader goal of quantifying the influence of woody debris on stream N dynamics: 1) Quantify changes in the short term (gross) uptake rate of NO3- in response to the addition or removal of woody debris in forested streams (measured using 15N-NO3- tracer releases). 2) Quantify differences in the net retention of NO3- within a forested stream reach in response to the addition or removal of woody debris (measured using a mass balance approach).
I will conduct experiments in three replicate watersheds across the northeast: HBEF in North Woodstock, NH, the Sleepers River Research Watershed in North Danville, VT, and the Model Forest in Claryville (Frost Valley), NY. At all three watersheds, a BACI study design will be implemented to quantify changes in nitrate uptake and retention in response to wood manipulations. This design isolates the experimental element and accounts for natural variation by comparing the difference (or ratio) between manipulated and unmanipulated streams before versus after the imposed treatment. I will use two complementary approaches to quantify N dynamics in this study: 1) tracer 15N-NO3- releases to measure short-term (gross) nutrient uptake (following LINX II protocols) and 2) a one month mass balance estimate of NO3- retention.
Headwater streams represent an important interface between terrestrial and aquatic ecosystems and results from this study will fit into a broader framework of research evaluating how stream nutrient dynamics change with the age of the upland forest. Results from this study, in combination with ongoing research into the recruitment and dynamics of woody debris in streams, will have application in modeling nitrogen export to lakes and coastal systems as forests across the northeast mature. This study will also assess the practical application of woody debris addition as a management tool to altering stream nutrient export from forested headwaters.