HR: 09:30h
AN: NB51C-05    [Abstracts]
TI: Integrating Hydrology and Ecology for Watershed Research in Topographically Rugged Landscapes: The Landscape Continuum Model
AU: * Williams, M W
EM: markw@snobear.colorado.edu
AF: University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Seastedt, T
EM: tims@snobear.colorado.edu
AF: University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: McKnight, D
EM: mcknight@snobear.colorado.edu
AF: University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Caine, N
EM: cainen@colorado.edu
AF: University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Liu, F
EM: fengjing@snobear.colorado.edu
AF: University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AB: Our Landscape Continuum Model (LCM) explicitly links terrestrial ecosystems to each other and to aquatic ecosystems in topographically rugged landscapes. The heart of the model is that strong linkages are generated among landscape components as a result of transport processes caused by extreme topography. These transport agents cause biogeochemical amplification and attenuation of processes not observed in most landscapes. We illustrate the LCM for alpine/subalpine aquatic systems with two decades of limnological research at the Niwot Ridge LTER site, located in the Colorado Front Range. Our measurements of streamwater quantity and quality show that the amount of inorganic nitrogen per unit catchment area exported downstream in stream water exceeds average wetfall inputs from the atmosphere near the mountaintops and then decreases downcanyon. Moreover, as elevation decreases, there is an almost linear pattern of increasing concentrations of dissolved organic carbon (DOC) and decreasing nitrate concentrations, suggesting retention and conversion of inorganic nitrogen to organic matter within aquatic communities. Consistent with the down-gradient increase in DOM is a switch from labile hydrophilic fractions of DOC in alpine systems to recalcitrant hydrophobic fractions of DOC in subalpine aquatic systems. Further, dual-isotope analysis of nitrate combined with end-member mixing analysis (EMMA) indicates that the snowmelt period begins with a dominance of atmospheric nitrate in stream water and then a gradual decline in atmospheric dominance and replacement by nitrate originating in talus fields. Additionally the flowpath results indicate a dominance of groundwater and return flow in stream water and also thus a dominance in biogeochemical control on nitrogen export in the groundwater of the basin after snowmelt.
DE: 1806 Chemistry of fresh water
DE: 1829 Groundwater hydrology
DE: 1845 Limnology
DE: 1860 Runoff and streamflow
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly