| Summary: | EPA Identifier: U915019 Title: An Examination of the Controls and Consequences of Nitrogen Limitation Among Ecosystems of the Colorado Front Range Fellow (Principal Investigator): Alexis A. Hartz Institution: University of Colorado at Boulder EPA Grant Representative: Virginia Broadway Project Period: January 1, 1996 - January 1, 1997 Project Amount: RFA: STAR Graduate Fellowships Research Category: Fellowship - Ecology and Ecosystems Description Objective: The objective of this research project is to understand the regional and global implications of disturbances and anthropogenic inputs on ecosystems. The main area of my project is ecosystems ecology, and in particular, biogeochemical cycling in terrestrial ecosystems. I focus my research on ecosystems that have been disturbed or have received excess nutrients from anthropogenic sources. Approach: I currently am considering a study that will examine the controls and consequences of nitrogen limitation among ecosystems of the Colorado Front Range, which is an ideal location to examine the questions that I would like to explore. Past research indicates that the area has received excess nitrogen inputs on the order of 30 times the preindustrial levels, which may have affected the nitrogen dynamics of the various ecosystems found in the Front Range (Sievering, et al., 1992). In addition, several studies have been performed in several ecosystem types that are part of, or immediately adjacent to, the Colorado Front Range. These ecosystem types include shortgrass prairies (Lauenroth, 1973), tallgrass prairies (Hopkins, in preparation), forests (Binkley, et al., 1992; Stottlemyer and Troendle, 1992), and alpine tundra (Bowman, et al., 1993; Sievering, et al., 1992). In this research, I would like to address several questions: 1. What are the sensitivities of the four identified ecosystems to nitrogen enrichment? 2. What are the controlling factors in the nitrogen cycle for each of the ecosystems? 3. How does the sensitivity of nitrogen enrichment of these ecosystems compare with similar ecosystem types in other regions of North America? To answer these questions, I am proposing a series of empirical studies to examine the responses of these ecosystems to nitrogen enrichment. Additional data collection is necessary because previous studies examining nitrogen dynamics in this region were incomplete in their characterization of sensitivity to nitrogen enrichment (T.R. Seastedt, personal communication). These studies also should determine the processes that control the nitrogen cycle in each of the four ecosystems. To complete this project, research of nitrogen limitation in other ecosystems in North America will be required to provide a detailed comparison with the nitrogen dynamics of the Colorado Front Range.
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