Dissertation Research: The Effects of Nitrogen Deposition on Ecosystem Function in the Forest-Alpine Tundra Ecotone

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Dissertation Research: The Effects of Nitrogen Deposition on Ecosystem Function in the Forest-Alpine Tundra Ecotone.Timothy Seastedt and Daniel LiptzinProposal #: 0508769 AbstractNitrogen pollution in the air and water is a growing problem for both ecosystem and human health. At low levels of nitrogen deposition from human sources, nitrogen fertilizes plants and soils. Once a critical threshold of deposition is reached, ecosystems can no longer retain nitrogen potentially leading to contamination of drinking water supplies. High elevation ecosystems in Colorado are thought to be on the verge of losing their ability to utilize these nitrogen additions from human activities. I propose to test a conceptual model which posits that the transition between the subalpine forest and the alpine tundra may be particularly sensitive to nitrogen deposition. During the winter strong westerly winds redistribute snow, and concomitantly, nitrogen pollution, in a predictable pattern around trees and across this transition zone. Because trees tend to capture snow, this interaction between trees and wind may create hot-spots of nitrogen deposition in the landscape. My experiments will examine the variation in nitrogen deposition and soil nutrients across the forest-tundra transition to test whether the predictable pattern of deposition translates into predictable effects on ecosystems and nitrogen retention. The broader impact of this research is to address concerns that nitrogen enrichment is affecting valuable ecosystem services (e.g., water purification) as well as altering relatively pristine environments. It will also determine if the forest-tundra boundary is a good indicator to monitor the nitrogen status of ecosystems.