Climate models predict that precipitation patterns will change in the coming decades, and in the U.S. Great Plains, the frequency and duration of summer droughts is predicted to increase. Because water is the most frequently limiting resource in arid and semi-arid systems, changes in water and nitrogen availability may cause linked carbon (C) and nitrogen (N) processes to become asynchronous, changing retention and loss patterns that control ecosystem function.

Morgan, JA, DP Smith and WJ Parton*; Shortgrass Steppe LTER; USDA-ARS and *Colorado State University, Fort Collins, CO

The 2007 Regional report by the Intergovernmental Panel on Climate Change predicted that the central grassland region of North America is very likely to warm substantially during the twenty first century. Modelers are less certain about changes in the timing and amount of precipitation in the region. Our research examines how changes in plant available water will affect critical biological processes in the central grassland region of North America, specifically comparing a site at the Shortgrass Steppe LTER to a site on the mixed grass prairie near Hays, KS.

Burrowing owls (Athene cunicularia) on the Pawnee National Grassland in Colorado nest on black-tailed prairie dog (Cynomys ludovicianus) towns where periodic extinctions from plague (Yersinia pestis) have been studied since 1981. Plague, a non-native pathogen, is typically lethal for prairie dogs and leads to loss of owl nest sites and other habitat changes that may affect owl productivity.

It is currently clear that both soil nutrient availability and consumers influence plant communities and that these factors may interact in interesting ways. However, the relative strengths of these factors and their interactions in terrestrial systems are still unclear. My goal is to generalize the relative impacts of nutrient availability and consumer control and their interactive effects on grassland communities across the precipitation gradient of the Great Plains, from shortgrass steppe through tallgrass prairie.

Increasing land fragmentation, mostly caused by urban sprawl and “leap-frog’ developments, is a major concern in many rapidly growing metropolitan cities of the US. Land fragmentation affects biodiversity and ecosystem processes, as portions of the landscape become isolated without connecting corridors and this, in turn, can change ecological structure and function. This cross-site comparative study, a joint-collaboration of several LTER sites (i.e.

Plant phenology - the seasonal timing of growth, reproduction, and senescence - can be measured from the scale of individuals to biomes. Understanding the timing of plant canopy development and how it is related to climatic variables is an important step in our understanding of how grassland ecosystems are being altered by a changing climate. In this poster we compare 2 years of plant canopy development in a dry year (2002) and an average precipitation year (2005).