Simulation and partition evapotranspiration for the representative landform-soil-vegetation formations in Horqin Sandy Land, China

Quantifying evapotranspiration (ET) and its components are particularly crucial to reveal the eco-hydrological processes in arid and semi-arid regions, such as the Horqin Sandy Land in China, but is lacking in existing literature. This study applied the Shuttleworth-Wallace (S-W) model to simulate and partition the ET at the representative landform-soil-vegetation formations (i.e., mobile dune, semi-fixed dune, and fixed dune) in Horqin Sandy Land based on the in situ data sampled by the meteorological monitoring system. Eddy covariance technology was used to validate the performance of the model. The results showed that the performance of the S-W model for clear days was better than that for cloudy or rainy days, and the S-W model would underestimate ET in rainy days. During 2017 growing season, ET showed as mobile dune (308 mm) < semi-fixed dune (333 mm) < fixed dune (352 mm), which was consistent with canopy coverage. Evaporation (E) showed as mobile dune (176 mm) > semi-fixed dune (84 mm) > fixed dune (75 mm), accounting for 57.1%, 25.2%, and 21.3% of ET, respectively. With the increase of canopy coverage, the effect of leaf area index (LAI) on E/ET increased; conversely, the effect of soil moisture decreased. There were significant differences in the variation of ET in the dry and wet periods. During the dry period, the desert vegetation maintained low water consumption and showed obvious “midday break.” Compared with transpiration from canopy, evaporation from soil was more sensitive to precipitation.