Variations of simulated water use efficiency over 2000-2016 and its driving forces in Northeast China

Water use efficiency (WUE), the ratio of gross primary production (GPP) over evapotranspiration (ET), is a critical index for understanding and predicting terrestrial ecosystem carbon-water interactions and their responses to climate change. However, the spatiotemporal variation in WUE and its controlling mechanism are poorly understood till now at regional/global scales, due to either limited data availability or uncertainties in current data streams. For overcoming such limitations, a remote sensing (RS)-based two-leaf Jarvis-type canopy conductance (RST-Gc) model was incorporated into a revised distributed hydrological model ESSI (version 3) to simulate ET. The hydrological model was validated against ET estimates from eddy covariance (EC) data and streamflow observations. A well validated global GPP dataset from Vegetation Photosynthesis Model (VPM) was then incorporated to estimate WUE for the period 2000- 2016 over Northeast China. Variations of the simulated ET, GPP and WUE were quantified and their responses to potential drivers (e.g., precipitation, temperature, net radiation, vapor pressure deficit, and lead area index) were analyzed at different timescales (monthly and inter-annual) across various ecosystems.