The Dependence of Ecosystem Water Use Partitioning on Vegetation Productivity at the Inter‐Annual Time Scale

Abstract

Evapotranspiration (ET) is an important component of the water cycle, and is also the central linkage between water, carbon, and energy fluxes (Katul et al., 2012;Wang and Dickinson, 2012). Ecosystem ET can be partitioned into two types of water use in terms of different pathways. One type is biotic water use through leaf stomata (i.e., transpiration, T) that is accompanied by photosynthetic assimilation processes through stomatal conductance (Keenan et al., 2010;Fatichi and Pappas et al., 2017). The other type is abiotic water use (i.e., evaporation from wet surfaces, E, including soil evaporation E s , canopy interception E i , etc.) that is largely determined by meteorological conditions (e.g., rainfall frequency and intensity, net radiation, etc.), and is indirectly related to vegetation characteristics (e.g., leaf area index (LAI), canopy structure, etc.) (Paschalis et al., 2018). Vegetation dynamics have intrinsically different relations with both water use pathways at the process level, and thus are important factors affecting the partitioning of ET (Raz-Yaseef et al., 2012;Wang et al., 2010). Therefore, exploring the effects of vegetation dynamics on ET partitioning is critical for understanding the role of vegetation ecophysiological processes and structure on ecosystem water use. Such understanding is of great significance for advancing our knowledge of the coupling relationship between water and carbon cycles and their responses to climate change.The spatiotemporal variations of ET partitioning (represented by the contribution of the biotic water use to total water use, T/ET) and the affecting factors have previously been extensively investigated. Temporally, at the intra-annual time scales (e.g., diurnal, daily, seasonal, etc.), T/ET has been found to be dependent on vegetation properties (e.g., LAI, vegetation cover, etc.) and abiotic factors (e.g., precipitation (P), radiation (R a ), temperature (T a ), vapor pressure deficit (VPD), soil moisture, etc.) (