Widespread woody plant use of water stored in bedrock

Summary

This 2021 Nature paper presents evidence that woody plants across diverse ecosystems commonly access water stored in fractured bedrock, challenging the traditional hydrological assumption that plant water uptake is restricted to shallow soil horizons. Through stable isotope analysis, the authors demonstrate widespread reliance on bedrock water sources amongst woody species, suggesting that subsurface geological structure plays a previously underappreciated role in plant water availability and ecosystem resilience. The findings imply that bedrock water storage may buffer vegetation against seasonal and long-term drought stress, with potential implications for understanding ecosystem responses to climatic variability.

UK applicability

The findings are relevant to understanding water availability in UK woodland and mixed farming systems, particularly in regions with fractured bedrock geology (chalk, limestone, sandstone aquifers). However, the study's emphasis on woody plant access to deep water sources may have greater applicability in water-limited or seasonally variable climates; UK conditions typically feature higher rainfall and may show different reliance patterns on bedrock water, though this remains an open question for British ecosystems.

Key measures

Stable isotope ratios (δ18O and δ2H) in plant xylem water; depth and origin of water sources utilised by woody species; seasonal variation in bedrock water reliance

Outcomes reported

The study measured stable isotope signatures in xylem water of woody plants across diverse ecosystems to determine the proportion and prevalence of water sourced from fractured bedrock rather than shallow soil horizons. Results demonstrated that woody plants commonly access and utilise water stored in subsurface geological structures, suggesting bedrock acts as a previously underappreciated water reservoir.

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