Published

9632851 Knapp A long-term ecological research program will be continued and expanded at the Konza Prairie LTER site in NE Kansas. Konza Prairie, a pristine tallgrass prairie is, arguably, the most intensively studied grassland site on earth. The 15 year old, broadly-based research program encompasses studies from the population, community, ecosystem and landscape ecology levels. These studies are linked by a theme that includes all the major abiotic and biotic factors influencing this ecosystem. Our central hypothesis is that fire, grazing and climatic variability are essential and responsible for the structure and function of tallgrass prairie. In contrast to many other grasslands where ecological processes are constrained by a single resource (e.g., water), organismic to ecosystem processes and dynamics in tallgrass prairie are products of a variety of limiting resources (water, light, nitrogen). Variability in, and switching among, these primary limiting resources are caused by both present and historical fire, grazing and climatic regimes. As a result of this complexity, and because grazing and fire regimes are managed in grassland systems worldwide, data from the Konza Prairie LTER program have relevance not only for understanding this grassland, but for broader ecological issues such as stability diversity questions and interactions between land-use, biodiversity and climate change. The proposed research includes continuation of long-term fire and grazing studies as well as short-term studies focused on key processes and mechanisms. Proposed new research includes studies of the effect of fire season, a fire-treatment reversal experiment in which watersheds that have been annually burned or unburned for 20 years will have their treatments reversed, comparative studies of bison vs. cattle as the dominant grazers, and a long-term study of how grazing, fire, climatic variability and agriculture affect annual carbon, water and energy budgets in tallgrass prairie. A key question addressed by the latter study is whether or not tallgrass prairie soils are a sink or source for carbon and how land-use (fire, grazing) and climate affects the carbon budget.