Land Use Change from Cotton to Biofuel Crops: Implications on Evapotranspiration and Energy Fluxes.

Land use change can influence the climate by affecting the regional energy and water balances.  The terrestrial surface energy balance is controlled by the interaction between incoming solar radiation and vegetation properties.  Depending on the surface characteristics, net radiation (R_n) is partitioned into components of energy balance, which include latent heat (LE), sensible heat (H), soil heat (G), and storage heat (S) fluxes.  The objective of this was to compare evapotranspiration and energy fluxes of cotton and two potential biofuel feedstock systems. The biofuel feedstock systems studied are biomass sorghum (Sorghum bicolor L.) and Old World bluestem (Bothriochloa bladhii (Retz) S.T. Blake). We also examined the effects of seasonal changes in net ecosystem production, weather, and soil moisture content on energy fluxes and canopy conductance characteristics. Data were collected in the 2013 growing season from three producer fields planted to cotton, biomass sorghum, and Old World bluestem (~250 acres) in the Texas High Plains region. Latent heat flux (evapotranspiration) between the vegetation and atmosphere was measured using eddy covariance flux method. Other environmental variables measured included air temperature and relative humidity, net radiation, global irradiance, precipitation, soil temperature, and soil moisture. Plant measurements taken include height, leaf area index, biomass, and yield. Our results indicate significant differences in evapotranspiration and energy fluxes of cotton compared to biomass sorghum and Old World blue stem. Results of additional analyses will be presented.