Water erosion shapes deformation in alpine meadow patches on the Qinghai-Tibetan Plateau

Increasing area of bare soil and shrinking meadow patches are a typical degradation process that occurs in alpine meadows on the Qinghai-Tibetan Plateau. The production of runoff and sediment during water erosion is one of driving force in evolution of bare soil and meadow patches. However, how water erosion affects the deformation and evolution of meadow patches remains unclear. Here the effects of water erosion on patch deformation and evolution were estimated via simulation experiments and model estimation. The results showed that water erosion clearly shaped patch morphology and promoted patch evolution. The lateral flow on the patch exhibited stronger erosive forces than the forward flow. The erosion volume and retreat length of the bottom section of the patches were significantly greater than those of the upper section. The upper mattic epipedon could rupture or collapse when the undercutting length reached the critical length of 31.90 +/- 0.54 cm, and the process was about 55 years or more. The average retreat rate of meadow patches simulated from 1950 to 2014 was approximately 4-10 mm y-1, and this rate will likely increase as climate change intensifies in the future. Therefore, the total time required for patches to evolve from formation to rupture or collapse may be even shorter than our estimates, and these findings will help to address challenges faced by meadow patch collapse. The study findings clarified the important role of water erosion in the shaping and evolution of meadow patches. Additional studies and longterm monitoring databases are needed to determine the impacts of abnormal rainfall on meadow patch evolution under climate change.