Ecology

Biology

Water transport

Transpiration

Vapour Pressure Deficit

Precipitation

Trait

Canopy conductance

Computer science

Botany

Hydraulic conductivity

Geology

Soil water

Stomatal conductance

Climate change

Mathematics

Geography

Water stress

Agronomy

Turgor pressure

Xylem

Water use

Environmental science

Mathematical analysis

Soil science

Water flow

Photosynthesis

Tree (set theory)

Programming language

Drought tolerance

Meteorology

Atmospheric sciences

Canopy

New Phytologist

Tree water use is central to plant function and ecosystem fluxes. However, it is still unknown how organ-level water-relations traits are coordinated to determine whole-tree water-use strategies in response to drought, and whether this coordination depends on climate. Here we used a global sap flow database (SAPFLUXNET) to study the response of water use, in terms of whole-tree canopy conductance (G), to vapour pressure deficit (VPD) and to soil water content (SWC) for 142 tree species. We investigated the individual and coordinated effect of six water-relations traits (vulnerability to embolism, Huber value, hydraulic conductivity, turgor-loss point, rooting depth and leaf size) on water-use parameters, also accounting for the effect of tree height and climate (mean annual precipitation, MAP). Reference G and its sensitivity to VPD were tightly coordinated with water-relations traits rather than with MAP. Species with efficient xylem transport had higher canopy conductance but also higher sensitivity to VPD. Moreover, we found that angiosperms had higher reference G and higher sensitivity to VPD than did gymnosperms. Our results highlight the need to consider trait integration and reveal the complications and challenges of defining a single, whole-plant resource use spectrum ranging from 'acquisitive' to 'conservative'.

Climate and functional traits jointly mediate tree water‐use strategies