DISSERTATION RESEARCH: Soil Organic Matter Controls Over Nitrogen Retention in Alpine Tundra

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Human activity has more than doubled the amount of available nitrogen on land, primarily through fertilizer production and the burning of fossil fuels. Though nitrogen often limits plant growth, too much nitrogen can deleteriously affect ecosystems in many ways, including causing losses in biodiversity, as well as leading to water quality problems. Surprisingly, these effects have been observed in Rocky Mountain alpine tundra, even at relatively low levels of atmospheric nitrogen deposition. Thus, alpine tundra may have a fairly low capacity to resist significant changes following increasing nitrogen inputs. While inputs and exports of nitrogen from the tundra are fairly well known, the controls over nitrogen retention and loss are poorly resolved. In particular, we need much more information on the potential role of the large organic matter pools contained in soils. We will apply a stable nitrogen isotope label to a range of chronic nitrogen fertilizer plots in alpine tundra. We will then trace the fate of this label over subsequent months and years; such information will show how and where excess nitrogen is stored and/or lost in alpine tundra ecosystems. These findings will enhance our understanding of how a highly valued ecosystem may respond to a major human-driven environmental change, and thus have the potential to inform national and regional environmental policy.