Introducing water factors improves simulations of maize stomatal conductance models under plastic film mulching in arid and semi-arid irrigation areas

Abstract

Plastic film mulching (PFM) in the cropland may alter biophysical conditions for crop growth, which may not be accounted for in existing stomatal conductance models. This can affect the accuracy of carbon–nitrogen-water cycle simulations for the soil-crop systems and hamper our understanding of internal mechanisms that control plant leaf stomatal conductance (gsw). To evaluate the simulations of PFM effects on gsw, the three models (i.e., Ball-Woodrow-Berry (BWB), Ball-Berry-Leuning (BBL), and unified stomatal optimization (USO) models) were used. The two model modification factors were leaf-air temperature difference (ΔT) and a water response function (f(θ)). A two-year maize (Zea mays L.) field experiment was conducted under different PFM (black, transparent, and no-mulch). The performance of the BWB model was poor under varying water status in the arid irrigation area. As for the BBL and USO models, the coefficient of determination and modified efficiency coefficient of the modified models increased 5.8%–90.6% and 6.5%–145.4%, respectively, compared with the initial models. The root mean square error and relative error of the modified models decreased 3.5%–67.9% and 4.8%–65.6%, respectively. The ΔT and f(θ) factors effectively improved the BBL and USO models, but the f(θ)-modified models performed better than ΔT-modified models under PFM. Overall, our results suggest that the maize land implemented with plastic film mulching has altered biophysical conditions, leading to significant changes in crop photosynthesis, leaf-air temperature difference and top-soil water conditions. Accurate estimates of stomatal conductance require the model to consider water response functions and leaf-air temperature difference, particularly in environmental conditions associated with different extents of water deficit or drought.