Characteristics of E. japonicus stomatal conductance under water-deficit stress using a nonlinear Jarvis modified model

Stomas are important gateways in the photosynthesis and transpiration of plant leaves. The stomatal size directly influences the photosynthetic and transpiration rates. However, the stomatal size is closely related to environmental factors. This study aimed to reveal the response principle between the leaf stomatal conductance of Euonymus japonicus   and related environmental factors under water stress using pot experiments. The present paper introduced the difference between the leaf and air temperatures (ΔT) based on the Jarvis model, as well as established the improved Jarvis model between stomatal conductance and environmental factors. After optimizing the model parameters by the least-square method, the parameters were verified by the crossing method. An artificial neural network model was then introduced and compared with the former two. The results showed that the simulation results of the improved Jarvis model were better than those of the Jarvis and artificial network models. Compared with the Jarvis model, the improved Jarvis model had RMS and MRE errors that were at least 65% smaller, as well as a correlation coefficient (R2)(R2) that was at least 10% higher. The improved Jarvis model simulation results were more uniformly distributed than the Jarvis model on both sides of the 1:1 regression line. Therefore, under a water stress condition, the improved Jarvis model is more appropriate to use in simulating the stomatal conductance relationship of E. japonicus with environmental factors.