Biology subjects

Decarsin, R.

Publications and source records attributed to Decarsin, R..

3 recordsLinked to original sources

bioRxiv2026

Rooting for water: Bridging Plant Hydraulics and Ecohydrology to Predict Drought Stress

Forests regulate climate and sustain biodiversity, but their resilience is increasingly threatened by drought-induced hydraulic failure, when xylem water transport is impaired by embolism. A critical but poorly constrained determinant of this risk largely due to limited observations of deep root water uptake is the amount of root-accessible (sub)soil water storage (SR), which governs land-atmosphere exchanges during prolonged dry periods. While ecohydrological theory has long suggested a balance between soil water storage in the rooting zone, vegetation growth and drought tolerance, this concept has not yet been integrated into predictive models of hydraulic failure. Here we propose a novel, process-based inversion framework that integrates ecohydrological optimality theory with principles of plant hydraulic to infer SR. Using the SurEau plant hydraulic model, we estimate the SR value that balances the costs of soil exploration with the avoidance of drought-induced hydraulic damage. Applied first to a well-instrumented Mediterranean Quercus ilex forest, the inferred SR closely matched independent neutron probe and eddy covariance measurements and accurately reproduced observed drought responses, including leaf water potential and sap flow dynamics. We then scaled the approach across European forests remotely-sensed data, to assess spatially explicit SR estimates and associated hydraulic failure risk. Across more than 20 species and sites, inferred SR and drought stress metrics aligned with field observations and outperformed estimates based on conventional soil databases or remote-sensing-only approaches. By linking plant physiology and ecohydrological theory within a scalable inversion framework, this approach improves predictions of forest drought risk under climate change.

ecology↗

bioRxiv2024

Multi-year drought strengthens positive and negative functional diversity effects on tree growth response

O_LIMixed-species forests are proposed as strategy to increase the resistance and resilience of forests to drought stress. However, evidence suggest that increasing tree species richness does not consistently enhance tree growth responses to drought. Moreover, tree diversity effects under unprecedented multiyear droughts remain uncertain, calling for a better understanding of the underlying processes. C_LIO_LIHere, we used a network of planted tree diversity experiments to investigate how drought-induced growth responses of individual trees are influenced by neighborhood tree diversity and the functional traits of the focal tree species. We analyzed tree cores (948 trees across 16 species) from nine experiments across Europe featuring gradients of tree species richness (1-6 species), which experienced severe droughts in recent years. Radial growth response to drought was quantified as tree-ring biomass increment using X-ray computed tomography. We applied hydraulic trait-based growth models to analyze single-year drought responses across all sites and site-specific responses during consecutive drought years for six sites as a function of neighborhood tree diversity. C_LIO_LIThe large variability in tree growth responses to a single-year drought was partially explained by the focal species hydraulic safety margin (representing species drought tolerance) and drought intensity, but independent of neighborhood species richness or functional trait diversity. However, tree diversity effects on growth responses strengthened during consecutive drought years and were site-specific, with contrasting direction (both positive and negative). This indicated opposing pathways of diversity effects under consecutive drought events, possibly resulting from competitive release or greater water consumption in diverse mixtures. C_LIO_LIWe conclude that tree diversity effects on growth responses to single-year droughts may differ considerably from responses to consecutive drought years. Our study highlights the need to consider trait-based approaches (specifically, hydraulic traits) and tree neighborhood scale processes to understand the multifaceted growth responses of tree mixtures under prolonged drought stress. C_LI

ecology↗

bioRxiv2023

Functional diversity reduces the risk of hydraulic failure in tree mixtures through hydraulic disconnection

Forest ecosystems are increasingly threatened by anthropogenic pressures, especially by the increase in drought frequency and intensity. Tree species mixtures could improve resilience to diverse global anthropogenic pressures. However, there is still little consensus on how tree diversity affects water stress. Although some studies suggest that mixing species with different drought response strategies could be beneficial, the underlying mechanisms have seldom been identified. By combining a greenhouse experiment and a soil-plant-atmosphere hydraulic model, we explored whether mixing a drought avoidant (Pinus halepensis) and a drought tolerant (Quercus ilex) tree species could reduce plant water stress (defined as the risk of hydraulic failure) during extreme drought, compared to their respective monocultures. Our experiment showed that mixing species with divergent drought response strategies had a neutral effect on the drought-avoidant species and a positive effect on the drought-tolerant species. The model simulations further suggested that the beneficial effect of mixture on plant water stress during extreme drought was related to changes in the hydraulic connection of the plant from both the soil and the atmosphere. The ability of the drought-avoidant species to disconnect from the soil and the atmosphere limits its exposure to water stress, whereas the ability of the drought-tolerant species to increase its hydraulic connection to the soil lowers its hydraulic risk. This study brings a new insight on the mechanisms and traits combinations improving drought resistance in diversified forests and plantations, with important implications for forest management under climate change.

ecology↗