A stand-replacing wildfire burned through the San Dimas Experimental Forest (SDEF) this past September. The SDEF has a 60-year record of watershed hydrology and a 20-year record of watershed nitrogen export for several watersheds. The intense understanding of pre-fire conditions at the SDEF presents a once in a lifetime opportunity to closely investigate the impacts of fire as an ecological disturbance in a chaparral ecosystem. Existing data at SDEF indicates that watersheds with more frequent fires have reduced streamflow and inorganic nitrogen export on long timescales compared to watersheds with less frequent fires. This existing data is especially important because it indicates an interaction between disturbance regime and the susceptibility of ecosystems to atmospheric deposition. More generally our results will be relevant to understanding disturbance in ecosystems and disturbance influences on hydrologic and biogeochemical processes. We intend to investigate four major questions in this post-fire environment. First, we will determine the relative control of fire frequency on sediment and nutrient export with an observational network and process based studies. Second, we will investigate the impact of changes in ET on watershed hydrology in the post-fire environment with a robust observation network. This observation system consists of several watersheds that were burned during the 1980's as part of a prescribed fire experiment as well as several control watersheds. Third, we will investigate how the high rates of N deposition influence vegetation recovery in the post-fire environment with vegetation surveys at SDEF and at a low deposition site in southern California. Finally, we will investigate how fire history affects watershed hydrologic and biogeochemical export. We will also prepare the ground for future studies with detailed assessment of digital elevation data at the forest taking advantage of fire to collect both on the ground and remotely sensed data as well as with preliminary measurements of ET with an eddy-flux system with time and equipment donated by the University of California, Irvine.

Broader Implications The pre-existing facilities and experimental framework (detailed fire history with differences between watersheds) provide a truly unique opportunity to investigate the impact of fire on the amount of water available for human use and the impacts of fire on water quality. Since fire is such a dominant ecosystem process in many ecosystems of the western United States, better information on the impact of fire on water resources and water quality is critical information for land managers. The research will also provide information on how air pollution and disturbance interact and influence the large-scale vegetation change currently occurring in California that threatens the unique biodiversity of the region. . Additionally the location of the San Dimas Experimental Forest in southern California with its diverse population and numerous undergraduate institutions provide a perfect opportunity for outreach to underrepresented groups in the environmental sciences: urban populations and minorities. The University of California, Riverside and Long Beach State University both serve predominantly minority populations.

National Science Foundation (NSF)
Division of Earth Sciences (EAR)
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L. Douglas James
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University of California Riverside
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