he Influence of Pre-settlement and Current High Plains Land Use and Land Cover on Atmospheric, Soils, and Vegetation Properties

Changes in land use and land cover can alter local and regional weather, hydrology, and ecosystem function. In the High Plains Region of the central and western United States (the area immediately east of the Rocky Mountains from South Dakota to Texas), human landscape modification from native grasslands to intensively managed croplands is especially striking. Before this shift was initiated in the mid-19th century, relatively continuous short-, mixed-, and tallgrass prairies dominated the region. In contrast, the current landscape is a mosaic of croplands (irrigated and non-irrigated), grasslands, reservoirs, and urban areas. Associated with the observed land-cover conversion over the last 150 years, land-atmosphere interactions, water cycling, and ecosystem functions have also changed. Our objective is to quantify the role of land-use and land-cover change in the High Plains in modifying precipitation, near-surface air temperature, soil moisture and temperature, and plant growth. To do this, pre-settlement land cover was derived from Küchler's (1964) map of potential native vegetation and present land cover was adapted from National Land Cover Data (NLCD, Vogelmann et al. 2001) and agricultural statistics. Further, the land-cover datasets were enriched with C4 vegetation fractions from Tieszen et al. (1997). The contrasting land-cover data were used to define the lower boundary conditions in a coupled plant, land-surface, and atmospheric model (GEMRAMS) running on a 10 km horizontal grid increment. To isolate the spatial and temporal effects of the altered land surface on atmospheric properties, precipitation, soil moisture and temperature, and plant growth, paired GEMRAMS simulations were performed using identical large-scale meteorological and soil conditions. In addition, dry, intermediate, and wet spring and summer meteorological conditions were used to examine sensitivity to precipitation variation among the simulations.