Abstract
Evapotranspiration (ET) is a key ecological process connecting the soil-vegetation-atmosphere system, and its changes seriously affects the regional distribution of available water resources, especially in the arid and semiarid regions. With the Grain-for-Green project implemented in the Loess Plateau (LP) since 1999, water and heat distribution across the region have experienced great changes. Here, we investigate the changes and associated driving forces of ET in the LP from 2000 to 2012 using a remote sensing-based evapotranspiration model. Results show that annual ET significantly increased by 3.4 mm per year (p = 0.05) with large interannual fluctuations during the study period. This trend is higher than coincident increases in precipitation (2.0 mm yr−2), implying a possible pressure of water availability. The correlation analysis showed that vegetation change is the major controlling factor on interannual variability of annual ET with ~52.8% of pixels scattered in the strip region from the northeastern to southwestern parts of the LP. Further factorial analysis suggested that vegetation greening is the primary driver of the rises of ET over the study period relative to climate change. Our study can provide an improved understanding of the effects of vegetation and climate change on terrestrial ecosystem ET in the LP.
Highlights
Recent researches have indicated that hydrological cycling has accelerated with climate change and anthropogenic effects, which would alter global land surface processes through ET9, 10
The good performance, as indicated by relatively high R2 and low root–mean – square-error (RMSE) and bias, indicates that the model has a good potential to be used for analyzing ET patterns in the Loess Plateau (LP)
The controlling mechanisms that lead to differences in ET between regions indicate that studies on ET trends should be carried out at regional scales[42]
Summary
Recent researches have indicated that hydrological cycling has accelerated with climate change and anthropogenic effects, which would alter global land surface processes through ET9, 10. ET is controlled by the combination of atmospheric evaporative demand (potential evapotranspiration), the energy available at the surface (solar radiation), and water supply[11, 12]. It is a large yet diverse part of the water budget and extraordinary heterogeneity in space-time[13]. Other studies have found that changes in meteorological variables may have a combined influence on the potential evapotranspiration of the atmosphere, and ET in the Yellow River Basin of China over the past 50 years[16]
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