Assessing the impact of the “Grain for Green” on regional water-energy cycle in the agro-pastoral ecotone, Northwest China

Authors: Chansheng He*, Western Michigan University, Xuejin Wang, Center for Dryland Water Resources Research and Watershed Science, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000, China. , Baoqing Zhang, Center for Dryland Water Resources Research and Watershed Science, Key Laboratory of West China’s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000, China.
Topics: Water Resources and Hydrology, Land Use and Land Cover Change, China
Keywords: Land use/cover change; Land surface temperature; Evapotranspiration; Precipitation; Land-atmosphere interaction; Agro-pastoral ecotone, Northwest China.
Session Type: Paper
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China has been implementing a large scale “Grain-for-Green” program for rehabilitation of ecosystems since 1999. However, little has been reported on the responses of the regional water-energy cycle to such a large scale land use/cover change (LUCC), especially in the agro-pastoral ecotone, Northwest China (APENWC). In this study, we examined the responses to various types of LUCC in the APENWC for the period of 1993 to 2010 using the weather research and forecasting (WRF) model. The performance of the WRF model was validated by multiple types of observations. Results show that the water-energy cycles in the region are strongly affected by vegetation dynamics. During the period of 1993 and 2010, the most obviously increased land cover types were the grassland and barren land, and the sharply decreased land cover types were shrublands and croplands in the study region. A significantly negative correlation between land surface temperature (LST) and albedo was found, associated with a 0.5 ℃ reduction in the annual mean surface temperature in the APENWC. The LUCC also resulted in reductions in precipitation by altering local ET and vapor flux cycles in the APENWC, and the study region contributed additional moisture from the local ET into the north of the region. The findings show that the grassland expansion reduces mean land surface temperature, which will delay germination of seeds and initiation of vegetation growth in spring. Increases in seasonal ET and reductions in seasonal precipitation will lead to soil drying, exacerbating risks of summer drought in the APENWC.

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