Abstract
Quantitatively identifying the influences of vegetation restoration (VR) on water resources is crucial to ecological planning. Although vegetation coverage has improved on the Loess Plateau (LP) of China since the implementation of VR policy, the way vegetation dynamics influences regional evapotranspiration (ET) remains controversial. In this study, we first investigate long-term spatiotemporal trends of total ET (TET) components, including ground evaporation (GE) and canopy ET (CET, sum of canopy interception and canopy transpiration) based on the GLEAM-ET dataset. The ET changes are attributed to VR on the LP from 2000 to 2015 and these results are quantitatively evaluated here using the Community Land Model (CLM). Finally, the relative contributions of VR and climate change to ET are identified by combining climate scenarios and VR scenarios. The results show that the positive effect of VR on CET is offset by the negative effect of VR on GE, which results in a weak variation in TET at an annual scale and an increased TET is only shown in summer. Regardless of the representative concentration pathway (RCP4.5 or RCP8.5), differences resulted from the responses of TET to different vegetation conditions ranging from −3.7 to −1.2 mm, while climate change from RCP4.5 to RCP8.5 caused an increase in TET ranging from 0.1 to 65.3 mm. These findings imply that climate change might play a dominant role in ET variability on the LP, and this work emphasizes the importance of comprehensively considering the interactions among climate factors to assess the relative contributions of VR and climate change to ET.
Highlights
Evapotranspiration (ET) is an essential component of both hydrological processes and surface energy exchange, which regulates water allocation to a land surface and plays an important role in water resource management [1,2]
We quantitatively evaluate the contribution of vegetation restoration (VR) and climate change to the ET on the Loess Plateau (LP) at the regional scale based on remote sensing products and the Community Land Model (CLM)
Along with the implementation of VR, vegetation coverage clearly increases on the LP, inevitably causing total ET (TET) change
Summary
Evapotranspiration (ET) is an essential component of both hydrological processes and surface energy exchange, which regulates water allocation to a land surface and plays an important role in water resource management [1,2]. The rate of evaporation from open pans of water in the Northern Hemisphere has been steadily decreasing in past decades, which is in contrast with the expectation that a warming climate should cause an increase in the rate of evaporation from terrestrial open water bodies [15]. These findings reveal the complexity of the interaction between climate variables and ET and the uncertainty of existing knowledge
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