The feedback of greening on local hydrothermal conditions in Northern China

Northern China has experienced a significant increase in vegetation cover over the past few decades. It lacks a comprehensive understanding of how greening impacts local hydrothermal conditions. To address this issue, in our study, the RegCM-CLM45 model was used to conduct a thorough assessment of the impacts of greening on temperature, vapor pressure deficit (VPD), precipitation, and soil moisture. The findings revealed that the local climatic effects of greening varied across different drought gradients based on the aridity index (AI). In drier regions with AI<0.3, the increased energy induced by greening tended to dissipate as sensible heat, exacerbating both warming and drought conditions. Conversely, in wetter regions with AI>0.3, a greater proportion of energy was lost through evapotranspiration, attenuating warming. Additionally, greening enhanced precipitation and soil moisture in drier regions and moderated their decline in wetter regions. Significantly, our research emphasized the effectiveness of grassland expansion and conservation as prime strategies for ecological restoration, particularly in drylands, where they could effectively alleviate soil drought. Given the diverse responses of different land cover transformations to local hydrothermal conditions in drylands, there is an urgent need to address potential adverse effects arising from inappropriate ecological restoration strategies and to develop an optimal restoration framework for the future.