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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Innovative Approaches 1
The influence of network structure on biogeochemical cycling in aridland watersheds
J.R. Welter, R.A. Sponseller, and S.G. Fisher. School of Life Sciences, Arizona State University, Tempe, AZ, USA 85287-4501
In aridland ecosystems, soil moisture is a major driver of biogeochemical processes, and varies spatially and temporally across a terrestrial-aquatic continuum from the dry upland environment, to large perennial streams. What is the role of terrestrial and aquatic components of the landscape in C and N storage and loss along this gradient? In order to estimate the contribution of different components of the watershed (terrestrial and aquatic) to C and N cycling, we monitored changes that occurred among nested channels spanning the terrestrial-aquatic continuum from the smallest channels visible in the landscape, to the main stem of Sycamore Creek. We measured changes in riparian canopy volume, litter production, soil moisture, and rates of denitrification and CO2 flux from riparian soils. Results indicate that while upland areas respond quickly to available moisture, exhibiting high rates of denitrification and CO2 loss, potential for C and N storage, as well as gaseous loss, increases on an areal basis with increasing channel order. Thus, since areal estimates of C and N storage and gaseous loss vary as a function of stream order, the structure of stream networks (size, shape, bifurcation ratio) may have important implications for biogeochemical cycling.
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