Thursday, November 19, 2009, 4:30PM - 5:30PM
Full title: "Elevational controls on organic and inorganic nutrients in stream waters, Boulder Creek Watershed, Colorado Front Range."
High-elevation ecosystems have become the focus of recent biogeochemical research due to their unique and complex processes, but also because these systems may serve as an early warning system for the potential effects of climate change. In the Colorado Front Range, it is expected that alpine areas will continue to experience greater annual precipitation, as well as an increase in atmospheric deposition of inorganic nitrogen. Past studies have shown that these mountain systems tend to amplify such environmental changes in specific areas of the landscape. The Landscape Continuum Model (LCM) proposed a conceptual framework for how mountain ecosystems accumulate and redistribute exogenous material from the atmosphere and endogenous material derived from the mountain itself, emphasizing the importance of transport processes and redeposition of nutrients and water across highly varying and complex terrain. This study tests the LCM by comparing and contrasting changes in organic and inorganic nutrients in stream waters of headwater catchments along an elevational gradient in the Colorado Front Range. Water samples were simultaneously collected at four gauged headwater catchments: (1) Green Lakes Valley (3,500 m); (2) Como Creek (2,900 m); (3) Gordon Gulch (2,400 m); and (4) Betasso (1,830 m). All water samples were measured for DOC, DON, DOP, nitrate and ammonium. Additionally, spectroscopic techniques were used to determine the source and quality of DOC. These measurements, along with supporting information on soil C:N ratios and climate data, allow us to determine how elevational position controls: (a) the redistribution of exogenous materials from the regional environment such as nitrate in wetfall; and (b) endogenous sources originating from montane areas such as DOC and DON, while controlling for catchment size, aspect, and underlying geology.