Spatio-Temporal Evolution Characteristics and Driving Analysis of Ecosystem Water Use Efficiency in Yangtze River Basin

Ecosystem water use efficiency (WUE) is a good explanation of the trade-off between water loss and carbon gain in ecosystems. Uncovering the spatio-temporal patterns of WUE and the underlying driving mechanisms can help to understand the ecological strategies of plants and water cycling processes in basins. This study employed a long time series of satellite remote sensing data of the Yangtze River Basin to analyze the spatio-temporal characteristics of ecosystem gross primary productivity (GPP), evapotranspiration (ET), and WUE from 2010 to 2019 by using trend analysis, variance decomposition, and Hurst index. In addition, it investigated the contribution of GPP and ET to WUE and the persistence of the trend of this contribution. The results show: ① The distribution of WUE in the basin shows a spatial pattern of increasing from upstream to downstream, with an inter-annual variation of 0.013 gc/(m²·a); ② The overall inter-annual variations in the contributions of GPP, ET, and their interactions to WUE in the basin are -0.0035, -0.0051 and 0.0096/a, and they varied considerably across climate zones; ③ The Hurst indexes for inter-annual variation in the contributions of GPP, ET, and their interactions to WUE in the basin were 0.51, 0.6, and 0.61, indicating that the persistence states were all positively but varied considerably across climate zones. The study elucidated the spatio-temporal patterns of WUE, as well as the intrinsic driving mechanisms, which was of great importance to dealing with the impact of environmental change on the carbon and water cycle of the ecosystem.