Flowering-Stage Heat Stress in Xinjiang Jujube Orchards: Spatiotemporal Evolution, Integrated Risk Assessment, and Multi-Scale Drivers

Résumé fourni par la source

Jujube is an important economic fruit tree in China, with Xinjiang being the largest production region, where flowering-stage heat stress threatens yield stability. Assessing heat risk in jujube orchards requires consideration of crop-specific phenological sensitivity and heat injury thresholds. Therefore, this study developed a Heat Injury Accumulating Index for jujube (HISj) to assess flowering-stage heat injury by integrating temperature–humidity stress and phenological sensitivity. A Hazard–Vulnerability–Exposure framework combined with Landsat image was applied for spatial heat risk assessment, atmospheric circulation analysis and interpretable machine learning were integrated to identify the drivers of hazard and vulnerability. Results show that HISj exhibited pronounced spatial heterogeneity and a distinct spatial dipole-like pattern, with higher values mainly concentrated in the oasis regions of eastern and southern Xinjiang, and an approximately six-year oscillation across most regions. High risk areas were mainly concentrated in Turpan, Yizhou District, and southern Bazhou, whereas Aksu, Kashgar, and most of Hotan were predominantly characterized by moderate-risk conditions. Climatic heat hazard and integrated orchard-scale risk were not spatially equivalent, with some intensively managed orchard areas exhibiting comparatively lower risk despite relatively strong meteorological heat stress. Variations in HISj were associated with the Western Pacific Subtropical High, Eurasian zonal circulation, and the India–Burma trough. NDVI was used as an observational proxy for orchard vegetation condition to characterize vegetation-based vulnerability. NDVI showed nonlinear associations with hydrothermal conditions and elevation, with threshold-like responses around 0.10–0.15 cm3/cm3 for soil moisture and around 800 m for elevation. The relatively weak and non-monotonic SHAP contribution of HISj to NDVI suggests that the association between meteorological heat stress and orchard vegetation conditions may vary with local environmental conditions. These findings provide a spatially explicit basis for understanding flowering-stage heat risk and supporting targeted adaptation in arid oasis jujube orchards.

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