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

论文研究：氮沉降对森林-高山苔原过渡带生态系统功能的影响。Timothy Seastedt和丹尼尔Liptzin建议#： 0508769摘要空气和水中的氮污染对生态系统和人类健康都是一个日益严重的问题。 在低水平的氮沉积从人类来源，氮施肥植物和土壤。 一旦达到沉积的临界值，生态系统就不能再保留氮，可能导致饮用水供应的污染。 在科罗拉多的高海拔生态系统被认为是在失去他们的能力，利用这些氮增加人类活动的边缘。 我建议测试一个概念模型，假定亚高山森林和高山冻原之间的过渡可能是特别敏感的氮沉降。 在冬季，强劲的西风重新分配雪，并伴随着氮污染，在树木周围和整个过渡区的可预测的模式。 由于树木往往会捕获雪，树木和风之间的这种相互作用可能会在景观中产生氮沉积的热点。 我的实验将研究氮沉积和土壤养分在森林-苔原过渡过程中的变化，以测试可预测的沉积模式是否会转化为对生态系统和氮保留的可预测影响。 这项研究的更广泛影响是解决氮富集影响宝贵的生态系统服务的问题（例如，水净化）以及改变相对原始的环境。 它还将确定森林-苔原边界是否是监测生态系统氮状况的良好指标。

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.