Response of Paddy Rice Ecosystems to Drought with Solar-Induced Chlorophyll Fluorescence over the Jianghan Plain, China, During 2000–2021

Frequent droughts seriously threaten rice productivity. Previous studies generally adopted uniform transplanting dates for rice pixels, with relatively limited attention to coexisting cropping systems. This study investigates drought responses of paddy rice ecosystems in the Jianghan Plain from 2000 to 2021 using satellite-derived solar-induced chlorophyll fluorescence (SIF), considering three cropping systems: conventional single-cropping rice (CSCR), double-cropping rice (DCR), and integrated farming of rice and aquaculture animals (IFRA). A pixel-specific phenological matching framework was developed to extract meteorological conditions and SIF values within the actual growing season for each rice pixel, with drought characterized by the standardized precipitation evapotranspiration index (SPEI). Results show that seasonal drought suppressed rice SIF, but the magnitude of decline was not linearly correlated with SPEI. DCR exhibited the greatest SIF reduction, possibly due to two consecutive growing seasons exposed to water stress, whereas IFRA showed the smallest reduction, potentially associated with persistent field water storage. The vegetative stage, particularly during tillering, was most sensitive to drought. Anomalously dry or wet pre-transplant moisture conditions may be associated with greater SIF reduction, while normal moisture conditions tend to produce milder SIF reduction. These findings highlight the importance of cropping system characteristics and phenological stages in modulating rice drought responses, providing insights into drought assessment and water resource management under diverse cropping systems.