Hyposensitive canopy conductance renders ecosystems vulnerable to meteorological droughts

Abstract

Increased meteorological drought intensity with rising atmospheric demand for water (hereafter vapor pressure deficit [VPD]) increases the risk of tree mortality and ecosystem dysfunction worldwide. Ecosystem‐scale water‐use strategy is increasingly recognized as a key factor in regulating drought‐related ecosystem responses. However, the link between water‐use strategy and ecosystem vulnerability to meteorological droughts is poorly established. Using the global flux observations, historic hydroclimatic data, remote‐sensing products, and plant functional‐trait archive, we identified potentially vulnerable ecosystems, examining how ecosystem water‐use strategy, quantified by the percentage bias (δ) of the empirical canopy conductance sensitivity to VPD relative to the theoretical value, mediated ecosystem responses to droughts. We found that prevailing soil water availability substantially impacted δ in dryland regions where ecosystems with insufficient soil moisture usually showed conservative water‐use strategy, while ecosystems in humid regions exhibited more pronounced climatic adaptability. Hyposensitive and hypersensitive ecosystems, classified based on δ falling below or above the theoretical sensitivity, respectively, achieved similar net ecosystem productivity during droughts, employing different structural and functional strategies. However, hyposensitive ecosystems, risking their hydraulic system with a permissive water‐use strategy, were unable to recover from droughts as quickly as hypersensitive ones. Our findings highlight that processed‐based models predicting current functions and future performance of vegetation should account for the greater vulnerability of hyposensitive ecosystems to intensifying atmospheric and soil droughts.

Community assembly influences plant trait economic spectra and functional trade-offs at ecosystem scales

“…Second, our trait–response correlations ( Fig. 3 ) reveal that both economic spectrum and hydraulic functional traits may be more useful for improving models of flux maximums than drought sensitivity patterns, extending beyond previous studies aiming to explore traits-ecosystem flux relationships that have not included hydraulic traits or considered species, community, and ecosystem scales together ( 12 , 13 , 41 ). Thus, identifying critical trait syndromes/functional axes underpinning whole-ecosystem sensitivity to drought stress and general metrics of drought sensitivity from flux dynamics are key model development avenues.…”

“…2 – 4 . We conducted this clade-specific analysis because it is common practice in both trait and flux studies ( 1 , 9 , 10 , 40 – 42 ) and differential trait–function relationships may be expected due to large differences in physiology, canopy structure, and boundary layer conditions ( 9 , 10 , 12 , 42 ). A site was classified as “gymnosperm-dominated” if more than 50% of its composition (typically basal area or stem density) was from gymnosperm species following previous studies ( 9 , 40 ).…”

Response of Leaf Photosynthesis–Transpiration Coupling to Biotic and Abiotic Factors in the Typical Desert Shrub Artemisia ordosica

“…Others believe that increasing temperature leads to increased saturated water vapour pressure inside and outside the leaves, thus, increasing stomatal conductance and enhancing photosynthesis and transpiration. In contrast, stomatal conductance and the photosynthetic rate of plants decrease because of the effect of photosynthetic enzyme activity when the temperature decreases [18,19]. Current studies on the mechanisms of plant photosynthesis and transpiration have started with the exploration of the mechanism of the porosity theory proposed by Farquhar [20] for the realisation of carbon-water coupling at the ecosystem scale using flux data.…”