Contributions of Climate Change, Vegetation Growth, and Elevated Atmospheric CO2 Concentration to Variation in Water Use Efficiency in Subtropical China

Ecosystem water use efficiency (WUE) plays an important role in maintaining the carbon assimilation–water transpiration balance ecosystems. However, spatiotemporal changes WUE subtropical region of China (STC) and impact driving forces remain unclear. In this study, we analyzed variation STC used ridge regression combined with path analysis to identify direct indirect effects climate change, vegetation growth, elevated atmospheric CO2 concentration (Ca) on interannual trend WUE. We then quantified actual relative contributions these drivers change based sensitivity variables trends themselves. Results reveal a mean 1.57 g C/m2/mm STC. The annual series showed descending decline rate 0.0006 C/m2/mm/year. average temperature (MAT) leaf area index (LAI) had strong positive WUE, while vapor pressure deficit (VPD) negative effect. Opposite offset each other, but overall there was total effect Ca VPD terms contribution, LAI, Ca, were main factors; LAI caused increase by 0.0026 C/m2/mm/year, decrease 0.0021 0.0012 respectively. dominated trend, although also factors. Other contributed less trend. results study have implications for ecological management restoration under environmental conditions regions worldwide.