Climate, Soil and Water Feedback to Carbon Cycle of Alpine Semi-Arid Desert Ecosystem in the Qinghai-Tibet Plateau

In the context of increasing global carbon emissions and relative water scarcity, it is of great significance to study the relationship between climate change and carbon-water coupling. This study aims to investigate the carbon-water process of at alpine desert at the east shore of the Qinghai Lake in the northeastern of Qinghai-Tibet Plateau. The results indicated that (1) the annual average values of net ecosystem exchange (NEE), evapotranspiration (ET), and water use efficiency (WUE) in study area were -696.9 g C·m-2, 834.07mm, and 0.84 g C·kg-1·H2O , respectively. (2) At the annual scale, NEE is mainly influenced by air temperature (Ta) and precipitation (P), while ET and WUE are dominated by Ta and soil temperature (Ts), and Soil water content (SWC) has relatively little influence on NEE, ET and WUE. (3) On the seasonal scale, NEE and ET showed the strongest performance in summer, followed by fall, spring, and winter, and Ta and vapor pressure deficit (VPD) were the main factors affecting the seasonal variation of NEE, ET, and WUE. (4) On the diurnal scale, Ta and VPD are the main influences on NEE and ET, and Ta and SWC are the main influences on WUE. P has a significant increase in its contribution to NEE, ET and WUE. Above all, the findings demonstrated that the alpine desert exhibits a strong carbon sink pool. We concluded that thermal conditions (Ta, Ts20, Ts40) were more crucial than moisture conditions (VPD, SWC20, SWC40) for carbon and water processes in alpine desert ecosystem. Given changeable of climate variability and localized thermal and hydrological conditions in future, reducing ET would be an approach that works well to improve WUE, meanwhile, the selection of appropriate species for water and carbon sequestration would be an effective way to maintain the ecological balance of alpine desert ecosystems.