Abstract
Grazing intensity effects on the evapotranspiration ( ET ) partitioning into evaporation ( E ) and transpiration ( T ) were investigated using eddy covariance measurement data during the growing season (May to September) from 2005 to 2008 over typical steppes in Inner Mongolia, China. Four grazing intensities were examined ( UG79 , ungrazed since 1979; WG , winter grazed; CG , continuously grazed; HG , heavily grazed). Soil water content ( SWC ) significantly influenced daily T / ET by affecting T and E in different ways. On a monthly scale, T / ET at UG79 (0.46–0.77) increased with vegetation growth regardless of the uneven distribution of precipitation. The mean T / ET at UG79 for the growing season ranged from 0.50 to 0.74 for 2005 to 2008. In the normal precipitation year (2006), WG and HG reduced T / ET because they significantly reduced T through the removal of leaf area. In the dry year (2005), this negative effect on T was depressed by summer droughts, while WG and HG decreased E primarily due to the decreased interception of rainfall by the canopy. The grazing effect on T / ET was opposite to that in 2006. These results indicate that grazing effects on ET partitioning could vary with soil water conditions in the semiarid typical steppe ecosystems.