Hydraulic Traits and Drought Responses in Vascular Plants

Vascular plants rely on a continuous water column within their xylem to transport soil moisture to leaves for photosynthesis and growth. Hydraulic traits—such as xylem conduit diameter, vessel density and vulnerability to embolism—govern the efficiency and safety of this transport under varying water availability. During periods of drought, plants must balance the risk of xylem air‐entry (embolism) with the need to maintain transpiration and carbon assimilation. Traits such as the water potential at which 50 % of hydraulic conductivity is lost (Ψ50) and the hydraulic safety margin (the buffer between typical operating water potential and embolism thresholds) are central to understanding species’ drought resilience. Osmotic adjustments, stomatal regulation and storage of non-structural carbohydrates further modulate the capacity to survive and recover from water deficits. Interactions among these traits underpin biogeographical distributions, influence ecosystem carbon balance and inform predictions of vegetation responses to climate change. Insights into trait coordination and variation across taxa are critical for refining vegetation models, guiding reforestation and conserving water-limited biomes worldwide.

Research from Nature Portfolio

Recent studies have provided a basin-wide assessment of Amazonian tree hydraulic safety margins, revealing that species in wetter regions tend to operate closer to their embolism thresholds, while those in drier zones maintain wider buffers. This variation in hydraulic safety margins predicts long-term biomass accumulation, with forests possessing greater safety margins showing enhanced carbon sequestration under moderate stress. In semi-arid woodlands, parallel declines in photosynthesis and growth under experimental drought challenge the notion that non-structural carbohydrate reserves accumulate when growth is limited. Instead, water potential drives simultaneous downregulation of both processes, indicating that carbon storage is co-limited by hydraulic status. A global mapping of assemblage-level hydraulic risk integrates species’ hydraulic traits with distribution data to forecast spatial patterns of drought-induced mortality. By combining vulnerability traits and edaphoclimatic niches, this approach improves predictions of vegetation die-off under future climate extremes.

Hydraulic Traits and Drought Responses in Vascular Plants publication trend

The graph below shows the total number of articles in hydraulic traits and drought responses in vascular plants across all publications each year (not limited to Nature Index journals).

Technical terms

Xylem embolism: Blockage of water‐transporting vessels by air bubbles, reducing hydraulic conductivity.

Hydraulic safety margin (HSM): Difference between the typical operating water potential and the water potential causing 50 % loss of conductivity.

Non-structural carbohydrates (NSCs): Stored sugars and starches mobilised to support metabolism during stress.

Turgor loss point: Leaf water potential at which cells lose turgor pressure, triggering stomatal closure and wilting.

Hydraulic conductivity: Measure of the ease with which water moves through xylem conduits under a pressure gradient.

References

1. Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests. Nature (2023).
2. No carbon storage in growth-limited trees in a semi-arid woodland. Nature Communications (2023).
3. Increased hydraulic risk in assemblages of woody plant species predicts spatial patterns of drought-induced mortality. Nature Ecology & Evolution (2023).
4. Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers. Plant Physiology (2008).
5. Dead or dying? Quantifying the point of no return from hydraulic failure in drought‐induced tree mortality. New Phytologist (2019).