Abstract
Warming-induced expansion in vegetation coverage and activity can accelerate the montane hydrological regimes. However, the climate impacts on ecohydrology of forested valleys of the Himalaya are uncertain. In this study, utilizing results of about three centuries of cellulose isotope chronologies (δ 13C and δ 18O) of dominant tree species, geo-chronological proxies, bio-geophysical dataset and simulations including satellite observations, we show an activation in the ecophysiological processes including evapotranspiration (ET) since the 1950s. Observation suggests rapid greening, while isotopic records indicate enhanced assimilation and transpiration in deciduous species vis-à-vis conifers post 1950s. Given strong vegetation-precipitation feedback and superimposed on the increasing trends of conducive atmospheric factors affecting valley-scale convective processes, intensification in forest ET is manifesting in a progressive enhancement in extreme rainfall events (EREs) since the last few decades. Results suggest that representation of ecophysiological processes and dynamics of seasonal moisture loading in observational and modelling framework is critical for understanding EREs under climate change.
Highlights
The terrestrial carbon and water cycles are strongly coupled (Lemordant et al 2018, Gentine et al 2019)
The Tibetan Plateau (TP) is a region of strong land–atmosphere coupling, which is susceptible to hydrological impacts with the increase in evaporative surface (Yao et al 2019, Liu et al 2020, Wu 2020)
Regional studies generally suggest an overestimation in precipitation, which is centrally attributable to evaporative surfaces and local latent heat flux (Liu et al 2020)
Summary
The terrestrial carbon and water cycles are strongly coupled (Lemordant et al 2018, Gentine et al 2019). In the past few decades, energy-water cycle over the Tibetan Plateau (TP) has changed significantly than rest of the globe (Yao et al 2019, Liu et al 2020, Wu 2020). The TP is a region of strong land–atmosphere coupling, which is susceptible to hydrological impacts with the increase in evaporative surface (Yao et al 2019, Liu et al 2020, Wu 2020). It is an isolated region of atmospheric moisture and a significant moisture source in the summer. Studies indicate a rapid increase in EREs in the past few decades (Shukla and Sen 2021)
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