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Hotspots of Nitrogen Cycling Activity in an Alpine-Subalpine Watershed on Niwot Ridge
Anthony Darrouzet-Nardi
University of Colorado at Boulder
Department of Ecology and Evolutionary Biology
| Within a watershed, certain areas or components
of it are likely to be hotspots of biogeochemical activity. This project
was designed to locate nitrogen cycling hotspots within a heterogeneous
alpine-subalpine watershed at the Niwot Ridge LTER site in the Front Range
of the Rocky Mountains, Colorado. I used spatially explicit sampling methods
to characterize soil moisture, soil temperature, pH, the nitrogen and
carbon concentrations and stable isotope ratios in light and heavy soil
fractions, nitrification rates, mineralization rates, and availability
of inorganic nitrogen. Nitrogen concentration and isotope data suggest
that within the forested areas, where plant diversity is limited to several
trees, there are clear associations of nitrogen cycling activity with
physical conditions such as temperature and moisture. However, within
the open tundra and subalpine meadows, there is more heterogeneity, which
may be associated with higher species diversity. There are also anomalous
isotope values associated with the swampy areas that form at the sideslope-toeslope
transition, suggesting that these are areas of interest for ecosystem
processing of nitrogen.
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