Investigating the Relationship Between Net Carbon Uptake and Evapotranspiration of Agroecosystems in the Southern Great Plains Using Eddy Covariance.

Relationship between carbon uptake and evapotranspiration (ET) is important for the assessment of water use efficiency. However, the understanding of this relationship at the landscape scale for different agroecosystems especially bioenergy systems in the Southern Great Plains is limited. The objectives of this research were (1) to investigate the relationship between net carbon uptake and evapotranspiration of high biomass forage sorghum (Sorghum bicolor L. Moench), cotton (Gossypium hirsutum L.), and old world bluestem grass (Bothriochloa baldhii Retz S.T. Blake), and (2) to assess the role of environmental variables in driving the carbon and ET fluxes. Continuous measurements of carbon dioxide and ET were made for three seasons along with other environmental variables in sorghum, old world bluestem, irrigated cotton, and dryland cotton field in Texas High plains. Eddy covariance system was installed in each field to make these measurements. Average gross carbon uptake of sorghum, irrigated cotton, dryland cotton and old world bluestem were 1664, 879, 422 and 854 g C m^-2 during the 2013 and 2014 growing seasons. Further analysis of the data is being conducted and the results will be presented at the meeting.