The role of land cover and precipitation variability on carbon and water fluxes in central US grasslands

Landcover and precipitation variability has a major impact on carbon and water cycling in grassland ecosystems. Understanding the response to these changes can help better assess potential impacts due to climate change and/or land use changes. The objective of this study is to examine the impact of land cover and precipitation variability on carbon and water fluxes of three different sites in Northeast Kansas. Two sites are located at the Konza Prairie near Manhattan, KS, which receives an annual average 835mm of precipitation. The “upland” site at Konza consists primarily of C4 grasses and is burned annually. The second site at Konza is experiencing woody encroachment and is burned every four years. The remaining study area is located at the Nelson Environmental Study Area (NESA) near Lawrence, KS. NESA receives an annual average of 937mm of precipitation and consists of a mix of C3/C4 grasses that is also experiencing woody encroachment. It is also burned every four years. Over two years (2007-2009) of eddy covariance data from each site is used to examine the impacts of changes in precipitation timing and magnitude as well as land cover composition on water and carbon cycling in the region. Special emphasis is placed on examining and comparing energy balance partitioning strategies in order to assess the impacts of land cover variability. Water use efficiency and Budyko curves are used to compare impacts of location along the precipitation gradient across the state of Kansas, and to assess the impacts of variation in annual rainfall. Understanding the impact of these factors is important for determining potential responses to climate change across the central United States.