Estimating canopy stomatal conductance and photosynthesis in apple trees by upscaling parameters from the leaf scale to the canopy scale in Jinzhong Basin on Loess Plateau.

The estimations of stomatal conductance and photosynthesis performed by upscaling the parameters from the leaf scale to the canopy scale are key points in the fields of forest ecohydrology and physiology. The foundation for solving this scientific problem is determining the optimal models for calculating the leaf stomatal conductance (g) and photosynthetic rate (P). In this study, we used the Jarvis model combined with modification factors, including leaf-air temperature (ΔT) and CO concentration inside and outside the stomata (ΔC), to estimate g and the new Ye light-response model to estimate the P of apple trees in Jinzhong Basin on Loess Plateau. The results show that the modified Jarvis (Jarvis) model and the new Ye light-response model could estimate g and P, respectively, with very high accuracy, with R values of 0.926 and 0.959 for the former, and 0.987 and 0.983 for the latter in 2019 and 2021, respectively. Then, we estimated the canopy stomatal conductance (g) and photosynthetic rate (P) by first dividing the apple tree canopy into sunlit and shaded leaves and then summing the contribution of sunlit and shaded g, P and leaf area index. Our efforts will be a valid reference for estimating the g and P of other tree or crop species in the future.