Global sensitivity analysis and uncertainty analysis for drought stress parameters in the ORYZA (v3) model

Abstract

AbstractDrought stress parameters in crop models have received little attention in the literature. In this study, a global sensitivity analysis on yield simulation was conducted for the drought stress parameters in the ORYZA (v3) model, and sensitive parameters were identified for double‐season rice (Oryza sativa L.) (early rice and late rice) by using the Extended FAST method in different scenarios involving two N applications, two soil types, and four depths of plough soil layer. An adaptive metropolis algorithm (MCMC‐AM) was used to quantify the uncertainties of these parameters with yield observations under various drought stress conditions. Based on the estimated parameter values, model performance of yield simulation was evaluated for drought stress conditions. Results showed that in a light drought stress situation, the upper limit factor for transpiration decline (FSWTD) was extremely sensitive at low N application, whereas the upper threshold for leaf expansion became more sensitive at high N application. In a moderate drought stress situation, the upper threshold for leaf rolling had high sensitivity under all conditions except for the late rice at low N application. In a heavy drought stress situation, FSWTD always had strong influence on yield, whereas the impacts of other parameters varied under different scenarios. Soil types and plough soil depth had considerable effects on the parameter sensitivities depending on fertilizer application and drought stress level. The empirical posterior distributions of these drought stress parameters for late rice showed very different shapes and variation ranges from that for early rice, and large uncertainties were presented. The yield simulations with a finely calibrated model were overestimated under heavy drought stress, especially for the late rice, which was grown in the dry season. The results highlighted that more attention should be paid for the drought stress parameters in crop models.