Effects of Land Use Change From Grassland Pasture and Wheat to Switchgrass in the Southern Great Plains

An inter-agency, interdisciplinary experiment to quantify the ecological and hydrological impacts of conversion of wheat and pasture lands to switchgrass (Panicum virgatum L.) production has been initiated in northwestern Oklahoma. Switchgrass is a promising biofuel feedstock for the production of cellulosic ethanol, especially in regions with limited precipitation and land that is marginal for crop production. Through this experiment, we will observe and quantify both the ecological and hydrological attributes of switchgrass such as water use efficiency, the temporal dynamics of carbon water and energy fluxes, and net primary productivity under natural climate variability. These results will improve our understanding of the feasibility of converting marginal land to switchgrass-based biofuel production in the semiarid Southern Great Plains. Our experiment is located on two fields owned by the USDA-ARS Southern Plains Range Research Station in Woodward, OK. One field was an established grassland pasture and the other a marginal wheat field. Both fields have been or are in the process of being converted to switchgrass production on a commercial scale. Both fields have been instrumented with identical eddy covariance towers for the measurement of CO2, water, and energy fluxes, along with associated atmospheric and soil parameters in late April of 2009, at the same time that site preparation began. We have also begun a comprehensive set of biometric and soil measurements. In addition to existing watershed flumes that had been installed and operated for over a decade at the pasture site, we are in the process of instrumenting the converted pasture and an adjacent, undisturbed pasture with soil moisture sensors. Collectively, we will study the effects of this land use change on streamflow, sediment production and groundwater recharge.