Larger contribution of evaporation from soil and thermokarst lake to local precipitation than plant transpiration in the permafrost regions of central Qinghai-Tibet Plateau

Permafrost degradation on the Qinghai - Tibet Plateau (QTP) have a direct impact on the evapotranspiration and moisture recycling process by changing underlying land surface conditions. Up to now, the contribution of thermokarst lake evaporation and plant transpiration to local precipitation in the permafrost regions of the QTP remains unknown. This study collected precipitation, thermokarst lake water, plant, and soil samples, and quantitatively estimated the proportional contributions of thermokarst lake evaporation, soil evaporation, and plant transpiration to local precipitation by the Bayesian isotopic mixing model in the permafrost region of central QTP. Results showed that the contribution of advection vapor to local precipitation was dominant, with a mean value of 74.6 %, and the moisture recycling ratio ranged from 19.7 ± 2.1 % to 29.7 ± 3.6 % (mean: 25.4 %). The mean contribution fraction of thermokarst lake evaporation and soil evaporation were 9.2 % and 8.9 %, respectively. Contrary to the findings of related studies in the nearby Qilian Mountains and arid central Asian oases, the total surface evaporation contribution of 18.1% was considerably higher than the 7.4% of plant transpiration in this study area, which was attributed to the rapid expansion of thermokarst lakes, sparse vegetation, and higher soil moisture condition in the shallow active layer.