From ecohydrology to ecosystem change: linking plant water use and plant water status during drought

Ecohydrology sits at the nexus of two important facets of the study of global environmental change: the description of the water cycle that accounts for the role of plants, and the prediction of plant vulnerability in response to water availability. The key to this feedback lies in knowing the water status of plants (i.e. water potentials), which regulates both plant water uptake and their physiological experience of stress. However, uncertainties remain in our understanding of how plant water status might vary as a product of physiological traits and local environmental conditions. Here, using a combination of models and field observations, we highlight some challenges and opportunities for incorporating plant hydraulic status into predictions of plant water use and drought stress. Specifically, we (i) contrast stress responses and health of woody species based on their landscape and hydrological settings during a multi-year drought, (ii) advocate for the use of simple models to separate the effects of intrinsic traits vs. external environment in determining plant water status, and (iii) demonstrate how incorporating plant hydraulic traits can improve predictions of plant water use, especially in cases where soil water availability may be decoupled from atmospheric water demand.