To reveal the characteristics of evapotranspiration and environmental control factors of typical underlying surfaces (alpine wetland and alpine meadow) on the Qinghai-Tibetan Plateau, a comprehensive study was performed via in situ observations and remote sensing data in the growing season and non-growing season. Evapotranspiration was positively correlated with precipitation, the decoupling coefficient, and the enhanced vegetation index, but was energy-limited and mainly controlled by the vapor pressure deficit and solar radiation at an annual scale and growing season scale, respectively. Compared with the non-growing season, monthly evapotranspiration, equilibrium evaporation, and decoupling coefficient were greater in the growing season due to lower vegetation resistance and considerable precipitation. However, these factors were restricted in the alpine meadow. The decoupling factor was more sensitive to changes of conductance in the alpine wetland. This study is of great significance for understanding hydro-meteorological processes on the Qinghai-Tibetan Plateau.

Soil infiltration processes were evaluated under field conditions by double-ring infiltrometers with different underlying surfaces in permafrost regions of the Tibetan Plateau. The results show that initial infiltration rates, stable soil infiltration rates and cumulative soil infiltration are strongly dependent on the underlying surface types, with the highest initial and stable soil infiltration rates in the alpine desert steppe, and the lowest in alpine meadow. The effects of soil moisture and texture on infiltration processes were also assessed. Within the same underlying surfaces, the values of infiltration parameters increased with the amount of vegetation cover, while soil moisture and soil infiltration rates displayed opposing trends, with fitting slopes of -0.03 and -0.01 for the initial and stable soil infiltration rates, respectively. The accuracies of the five models in simulating soil infiltration rates and seven models in predicting cumulative infiltration rates were evaluated against data generated from field experiments at four sites. Based on a comparative analysis, the Horton model provided the most complete understanding of the underlying surface effects on soil infiltration processes. Altogether, these findings show that different underlying surfaces can alter soil infiltration processes. This study provides a useful reference for understanding the parameterization of land surface processes for simulating changes in hydrological processes under global warming conditions in the permafrost region on the Tibetan Plateau.