The Effects of Anthropogenic Nitrogen Deposition on the Functioning of Alpine and Subalpine Ecosystems Nitrogen Cycling and Trace Gas FluxesEPA Grant Number: R823442
Title: The Effects of Anthropogenic Nitrogen Deposition on the Functioning of Alpine and Subalpine Ecosystems Nitrogen Cycling and Trace Gas Fluxes
Investigators: Schmidt, Steven K. , Bowman, William , Williams, Mark
Institution: University of Colorado at Boulder
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1995 through September 1, 1998
Project Amount: $329,280
RFA: Exploratory Research - Environmental Biology (1995) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Health , Ecosystems
Description:This research examines the fate and effects of increased nitrogen (N) deposition in high elevation regions of the Rocky Mountains. With increased urbanization of the West, deposition of anthropogenically produced nitrogenous compounds has increased dramatically in recent years. High mountain regions often receive a disproportionate amount of these pollutants because of high amounts of orographic precipitation. In particular, the high-elevation areas of the Colorado Front Range receive increased amounts of pollutants from power plant emissions during westerly storms and from the Denver urban corridor during easterly storms.
Studies will be conducted at several sites in the Rocky Mountains, to determine the effects of different levels of atmospheric N deposition on key ecosystem processes. The key ecosystem processes being studied are: 1) the immobilization of deposited N into microbial and plant biomass, 2) the effects of deposited N on plant and microbial production and functional diversity, and 3) the production and consumption of atmospheric trace gases (e.g., CH4 and N2O) in response to increased N deposition. In addition to studying these processes at different sites, fertilization experiments are also underway to determine the threshold levels of N inputs that result in: a) increases in leaching and gaseous losses of N from alpine soils, and b) changes in plant community structure and microbial functional diversity.
Finally, special emphasis is being given to the fate and effects of N inputs from the winter snowpack which enters the ecosystem as a large pulse during snowmelt in the spring. The solutes stored in the snow pack are released rapidly during the initial phase of snowmelt. Nitrogen concentrations in these meltwaters can be 5 to 10 times greater than their original concentrations. Biotic uptake of N during snowmelt may be constrained by low temperatures. Preliminary studies indicate that there is a significant amount of microbial activity occurring under the snow pack in the spring, even well before snowmelt. Thus, the potential exists for much of the N deposited in snow to be either assimilated into microbial biomass or lost as N2O, NO, or N2.