Eco‐Hydrological Connectivity in Soil–Vegetation–Atmosphere Continuum in a Tropical Biodiversity Hotspot

Uptake and distribution of soil water by vegetation is a dynamic phenomenon, which is of utmost importance due to its role in the hydrological cycle and terrestrial productivity. Despite the significance, the soil water–vegetation interaction remains unexplored in large parts of the world, particularly in the tropical forested regions. This study, through measurements of oxygen isotopic compositions (δ 18 O) of water in different hydrological components, such as streams, xylem, groundwater, root and soil pore water, focused on understanding the eco‐hydrological connectivity during the dry season in a tropical humid forest (Western Ghats, India—a biodiversity hotspot). The results indicated that only 12% of the riparian trees primarily accessed stream water, and the dominant portion (36%) of the trees showed lower δ 18 O than the expected (sampled) sources, indicating access to an unsampled/deeper water source, probably accessed only during the summer season to withstand low plant water potential. We explain this isotopic difference by differential access to shallow, deep and redistributed soil water, providing insights into the contribution of multiple water sources to transpiration. Hydraulic redistribution (i.e., root‐mediated transport of deep water to upper soil layers) served as a critical water source for shallow‐rooted plants, helping them meet their water requirements during dry periods. Evidence for limited percolation of water into deeper soil due to quick filling of shallow soil pores during short and heavy precipitation events was noticed, highlighting the importance of continuous moderate rainfall for effective water percolation into the deeper soil.