The Role of Natural Legacy on Ecosystem Structure and Function in a Polar Desert: The McMurdo Dry Valley LTER Program

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9810219LYONSThe McMurdo Dry Valleys (MCM) region is among the most extreme deserts in the world; far colder and drier than any other Long Term Ecological Research (LTER) site. The biological systems within the MCM are relatively simple with no vascular plants and vertebrates. During the first six years of this LTER project, the perennially ice-covered lakes, ephemeral streams and extensive areas of soils were investigated in order to assess the role of physical constraints on the structure and function of the ecosystem. It is clear that the production of liquid water in both terrestrial and aquatic portions of this environment is a primary driver in ecosystem dynamics. Thus, the role of present day climatic variation is extremely important. However, one of the most significant discoveries was that past climatic legacies strongly overprint the present ecological conditions in MCM. In the second phase of this LTER, the research will be extended through the continuation of the investigation of the MCM as an "end-member" system, with the aim to better ascertain the role of the past climatic legacies on ecosystem structure and function. The conceptual model now includes legacy as an important regular of MCM. A series of eight hypotheses in three major focus areas: hydrology, biological activity and diversity, and biogeochemical processes will be tested through a continuation of monitoring programs and long-term experiments. Understanding the structure and function of the MCM ecosystem requires understanding hydrological response to climate both now and in the past. Current patterns of biological activity and diversity reflect both past and present distributions of water, nutrients, organic carbon and biota. Biogeochemical processes responsible for the transport, immobilization, and mineralization of nutrients and other chemicals provide the linkages between the MCM biota and the physical environment. The timing, duration and location of biogeochemical processes in the past and present are controlled by water availability. Efforts will continue to focus on the integration of the biological processes within and among the lakes, streams and terrestrial ecosystems comprising the MCM landscape. The interdisciplinary research team plans to continue to use modeling and other integrative studies to synthesize data and to examine the knowledge of the MCM ecosystem.