| Summary: | Grasslands in the Southern Great Plains of the United States have major ecological and economic importance, with strong climate and water cycle connections. The historic native prairie grassland has been managed differently for enhancing productivity, while consequently altering water vapor fluxes. However, little is known about the impacts of different management activities on evapotranspiration (ET) at different spatio-temporal scales. In this study, we quantified and compared ET between co-located introduced managed pasture (MP) and native prairie (NP) pasture. Additionally, we compared the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived ET at four different spatial scales: 30 m (ET<sub>MOD30</sub>), 200 m (ET<sub>MOD200</sub>), 500 m (ET<sub>MOD500</sub>), and 1000 m (ET<sub>MOD1000</sub>) with eddy covariance-measured ET (ET<sub>EC</sub>). Large differences in ET<sub>EC</sub> were observed between two pastures from half-hourly to seasonal scales, with variations mainly controlled by the amount of rainfall and management activities. The results demonstrated differential responses of MP and NP in a pluvial year. The ET<sub>MOD30</sub> showed a better agreement with ET<sub>EC</sub> than did the ET<sub>MOD200</sub>, ET<sub>MOD500</sub>, and ET<sub>MOD1000</sub>. The ET<sub>MOD200</sub>, ET<sub>MOD500</sub>, and ET<sub>MOD1000</sub> largely underestimated ET<sub>EC</sub>, most likely due to their inability to capture the spatial heterogeneity of vegetation growth impacted by various management activities. Our results facilitate understanding of the difference in ET of MP and NP due to differences in vegetation resulting from different management activities and their differential responses to precipitation.
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