Characterization of ecohydrological indicators (EHIs) in India: a multi-scale perspective

The biogeochemical source and sink dynamics of terrestrial ecosystems play an important role in balance of carbon in the atmosphere. These biogeochemical processes such as carbon, water and energy cycles were affected by climate change and hydroclimatic disturbances. Hence, it is essential to understand the spatiotemporal variations and drivers of different ecohydrological indicators (EHIs) which links the carbon, water and energy cycles. This study assesses the three EHIs, namely water use efficiency (WUE_e), rain use efficiency (RUE_e), and light use efficiency (LUE_e), as well as their drives based on Net Primary Productivity (NPP) in India from 2002 to 2017 at river basin, climatic zone, and land cover scales. All the three EHIs were found to be higher in forest ecosystems which are high productive regions. The mean annual WUE_e and RUE_e showed a slightly decreasing trend, and the mean annual LUE_e experienced a slightly increasing trend. The ecosystem-based study shown that WUE_e and LUE_e in semi-arid zones and shrubland ecosystems experienced a positive trend. A similar trend was observed in RUE_e for arid and shrubland ecosystems. The drivers investigated includes 11variables, CO₂ concentrations, evapotranspiration (ET), humidity, leaf area index (LAI), normalized difference vegetation index (NDVI), precipitation (PRECIP), soil moisture (SM), solar radiation (SR), temperature (TEMP), vapor pressure deficit (VPD), and wind speed (WS). TEMP and SR were found to be more sensitive drivers of EHIs. Other drivers such as VOD, SM and humidity also played a significant role in local scales. This study will enhance our understanding of variations in EHIs and their mechanisms which can be a reference in predicting the ecosystem responses and resilience to changing climate and climate extremes.