Investigating Plant Responses to Water Stress via Plant Hydraulics Pathway

Abstract. Drought-induced plant hydraulic failure is one of the main factors for large-scale plant mortality. Understanding the response of the plants to water stress is of paramount importance to elucidate the dynamics of water, energy and carbon fluxes under drought conditions. In this study, we implemented the plant hydraulics pathway in STEMMUS-SCOPE (hereafter as STEMMUS-SCOPE-PHS) by considering xylem vulnerability, and validated the model at a karst site in Chongqing, China. Plant water potentials of root, stem and leaf are calculated in STEMMUS-SCOPE-PHS. A leaf water potential-based plant water stress factor (PHWSF) replaces the original soil moisture-based water stress factor to represent the effect of water stress on plant growth. Results show that the PHWSF captures the diurnal dynamics of water stress. The STEMMUS-SCOPE-PHS improves the simulation of diurnal dynamics of latent heat flux, net ecosystem exchange and gross primary production compared to STEMMUS-SCOPE with the value of Kling-Gupta efficiency (KGE) increasing from 0.74 to 0.83, 0.57 to 0.76, and 0.57 to 0.80, respectively. This research delineates the plant hydraulic responses to water stress and highlights the importance of leaf water potential in reflecting the plant water stress.