Warming & N Deposition in Alpine Environments
Boulder Creek watershed encompasses a large ecosystem gradient spanning plains, montane and alpine environments, in the Front Range of the Rocky Mountains. The high elevation systems are particularly vulnerable to the added nitrogen input given their minimal vegetation cover, resulting in elevated inorganic nitrogen concentrations in lakes and streams. In collaboration with researchers affiliated with the Niwot Long Term Ecological Research Site, we are exploring how warmer and dryer conditions over the last decade has altered the processing and export of atmospherically derived nitrogen within the alpine ecosystem. It appears that the disappearance of the cryosphere has led to increased rates of mineralization and nitrification, leading to greater exports of inorganic nitrogen despite recent decreases in atmospheric deposition flux.
You can read an article on this work in the CU Arts & Sciences bulletin, “Warming trend boosts nitrogen in Boulder watershed,” here
- Barnes, R.T., M.W. Williams, J.N. Parman#, K. Hill, & N. Caine. 2014. Thawing Glacial and Permafrost Features Contribute to Nitrogen Export from Green Lakes Valley, Colorado Front Range, USA, Biogeochemistry, doi:10.1007/s10533-013-9886-5
In collaboration with Meredith Hastings (Brown) and Jill Baron (USGS, Fort Collins), we are following up on this work by examining the sources of nitrogen within the cryosphere. Several studies (e.g. work by Jasmine Saros) have documented that alpine catchments with glacial features export more nitrate than similar systems without rock or snow glaciers. Is this nitrate simply frozen atmospheric deposition, released to the ecosystem during thawing? Is the nitrate the product of increased mineralization rates in these systems? Initial work is focused on understanding the spatial and temporal heterogeneity of the isotopic signal of the nitrate (δ15N-, δ18O-, Δ17O-NO3–).
This new work is driven by the amazing Sydney Clark, a PhD Candidate at Brown University. Thanks to her efforts we have new seasonal samples of ice, snow, water, and soil from both Loch Vale and Niwot catchments. Sydney has also examined the isotopic variability within long term precipitation samples (NADP sites). See recent AGU abstract.