Compound dry/wet and hot extremes decreased wheat/maize yield revealed by SHAP-RF and R-Vine Copula

Abstract

Context

Global warming is intensifying compound climate extremes, such as compound dry/wet and hot days (CDHD/ CWHD), posing severe threats to agricultural productivity and food security. Traditional risk assessments often focus on single climatic hazards, underestimating the synergistic impacts of compound events on crop yields, particularly for major staples like wheat and maize in China.

Objective

This study aims to systematically evaluate the spatiotemporal dynamics of CDHD and CWHD during the growing seasons of winter/spring wheat and spring/summer maize across China’s six major agricultural regions from 1961 to 2023, and to quantify their nonlinear impacts on crop yields using modeling frameworks.

Methods

The Non-Stationary Standardized Precipitation Evapotranspiration Index (NSPEI) and dynamic thermal thresholds were used to identify CDHD/CWHD. Crop yields under rainfed (water-stressed) conditions were simulated using the DSSAT-CERES model, rigorously calibrated and validated with field data. The Shapley Additive Explanation-Random Forest (SHAP-RF) method quantified the relative contribution of climatic variables to yield variability, while the R-Vine Copula function estimated yield reduction probabilities under varying compound stress conditions.

Results

and conclusions: (1) The frequency and intensity of CDHD and CWHD increased significantly (p < 0.001), with CDHD occurring more frequently than CWHD; (2) Compound events explained yield variability (up to 47.3 % relative importance) more effectively than single climatic factors, with CDHD exhibiting the strongest negative impact; (3) Spring maize and spring wheat were highly sensitive to CDHD, with yield reduction probabilities reaching 0.70–0.85, whereas winter wheat showed greater tolerance (probability: 0.57); (4) Regional heterogeneity was evident, e.g., summer maize yield in the Loess Plateau was negatively correlated with precipitation due to nutrient leaching from heavy rainfall.

Implications

or significance: This study provides a novel, interpretable framework for assessing compound climate impacts on agriculture, highlighting the critical role of CDHD in driving yield losses. The findings support the development of climate-resilient cropping systems and targeted adaptation strategies, facilitating a shift from single-risk management to integrated multi-stress regulation in a warming climate.