Spatiotemporal patterns of solar-induced chlorophyll fluorescence and its climatic associations across karst landforms in Guizhou, China.

Solar-induced chlorophyll fluorescence (SIF) reflects vegetation photochemical efficiency and photosynthetic activity and is therefore widely used as an indicator for assessing vegetation responses to climate change. Although vegetation photosynthetic activity in karst regions exhibits pronounced spatial heterogeneity associated with climatic variability, studies investigating the spatiotemporal dynamics of SIF and its climatic associations across different karst landforms remain limited. In this study, representative karst landforms in Guizhou Province, China, were selected as the study area. Based on growing-season SIF and meteorological data from 2000 to 2022, the spatiotemporal patterns of SIF and its statistical associations with climatic factors were analyzed. The results showed an overall increasing trend in SIF across the study area, with significant and highly significant increases covering 88.84% of the total area. The relative contributions of climatic factors to SIF varied considerably among karst landform regions. Air temperature exhibited the highest relative contribution in high-altitude regions, whereas solar radiation exhibited the highest relative contribution in low-altitude regions. Further analysis indicated nonlinear SIF-climate associations, including estimated RHU response-transition points of around 78-83% and landform-dependent nonlinear temperature response patterns. In addition, SHAP interaction effects varied across different combinations of climatic factors and landforms. Overall, the SHAP-assisted analysis showed that different karst landform regions exhibited distinct associations between SIF and climatic factors, suggesting that geomorphic context should be considered in regional assessments of climate-associated SIF variability in karst ecosystems. These findings provide useful references for landform-specific assessment of SIF-climate associations and ecological monitoring in the karst regions of Guizhou Province.