Overview: Our SGS site encompasses a large portion of the Colorado Piedmont Section of the western Great Plains. The extent is defined as the boundaries of the Central Plains Experimental Range (CPER), which is managed by the Agricultural Research Service (ARS), and the Pawnee National Grassland (PNG), which is managed by the US Forest Service. Expansion into the PNG has allowed us to explore the biotic interactions of the SGS ecosystem across a range of climatic, geologic, topographic and land use conditions. The CPER has a single ownership and landuse (livestock grazing). The PNG is characterized by a mosaic of ownership and land use. Ownership includes federal, state or private and land use consists of livestock grazing or row-crops. There are NGO conservation groups that exert influence over the area, particularly on federal lands. This varied land use and diversity associated with land users and managers substantiates the importance of the sgs-lter to the area.
History: The SGS LTER project represents the continuing development of a research tradition that began with the US/IBP Grassland Biome project in the late 1960's, the time at which ecosystem science was formally recognized as a sub-discipline in ecology. Research at the CPER over the past 20 years has had an important interactive relationship with the development of ecosystem science. The Grassland Biome project focused on the issue of productivity of natural ecosystems. Grasslands were conceptualized as homogeneous entities, appropriately described by an average square meter. The transition from the IBP project in the early 1970's to the LTER project in the early 1980's involved a change in thinking about the importance of spatial variability.
Research Topics: The shortgrass steppe (SGS) LTER has been in operation since 1982. The key questions that guide our work are:
1. What factors regulate SGS ecological structure and function over space and time?
2. How do the factors that regulate ecological structure and function, and the coupling of biotic and abiotic components, vary spatially and temporally within the SGS?
3. What are the biotic and abiotic thresholds that determine the vulnerability of the SGS to changes in the factors influencing ecological structure and function?