Emerald Lake and the Tokopah Valley in the Sierra Nevada (California) have been the focus of sustained limnological and watershed research since 1983. Knowledge gained through this research has transformed our understanding of how the thousands of lakes and watersheds in the Sierra Nevada are responding to global change.

Studies were initially motivated by concerns over the impact of acid deposition on aquatic ecosystems (1983-1989) and included integrative investigations of hydrologic and biogeochemical processes in lakes and watersheds.

Later research emphasized remote sensing of snowmelt and lake and watershed responses to atmospheric deposition of nutrients and interactions with climate variability (1990-2001).

Beginning in 2002, seasonal transitions and nitrogen biogeochemistry became the focal point of our research efforts (2002-2006).

Through funding from the National Science Foundation-Long-term Research in Environmental Biology program, long-term observations of the responses of lakes and watershed to climate variability and atmospheric inputs have continued through the present. This work has provided new information on the role of phosphorus cycling in long-term changes in lake trophic status, expanded the time horizon of our observational records through paleolimnology and provided new insights into snowpack influences on hydrochemistry of Sierra Nevada lakes and streams.

Throughout this period of study, our research activities have benefitted air quality regulation in California, Federal management of wilderness areas in the Sierra Nevada and student education spanning K-12, undergraduate and graduate levels. This work is represented by the 159 peer-reviewed publications, technical reports and graduate theses and dissertations (see Publications).