Meta-analysis of the effect of grazing on grassland evapotranspiration in China

Grasslands are important components of terrestrial ecosystems, and grazing is a key way in which grasslands are utilized and managed. In this study, 23 experimental results of grasslands in China were analyzed using meta-analysis. These results showed that the average effect size of grazing on evapotranspiration of grassland ecosystems was approximately −0.21 ± 0.04, and grazing activities significantly reduced the evapotranspiration of grasslands in China (P < 0.001). Furthermore, the order of decreasing average effect size of different grassland types was: meadow grassland, steppe, alpine grassland, and desert grassland. Except for desert grassland, grazing significantly reduced the evapotranspiration of the other grassland types. In addition, grazing intensity had a significant effect on the average effect size, and the order of influence on evapotranspiration was: heavy, light, then moderate. Thus, moderate grazing reduced evapotranspiration least, which was beneficial for the reduction of soil water loss. Both soil organic matter and total nitrogen had significant effects on the average effect value (P < 0.05), which could explain the effect value variation of 50.48% and 23.14%, respectively. In addition, future effective restoration of degraded grasslands and the improvement of soil organic matter and total nitrogen content will potentially reduce the average effect value of grazing on evapotranspiration, reduce the loss of soil water, and improve water use efficiency.