Contrasting Latitudinal Diversity Gradients in Karst and Non‐Karst Forests: Evidence for Bedrock‐Driven Modulation

ABSTRACT Aim Plant diversity is essential for ecosystem stability and the delivery of ecosystem services. While climate, through energy and water (i.e., productivity), is the primary driver of the latitudinal diversity gradient (LDG), edaphic conditions modulate resource storage and heterogeneity. The role of bedrock‐driven edaphic gradients in shaping LDG patterns remains poorly understood. Here, we tested how edaphic conditions interact with climate to shape species diversity and LDG patterns, underscoring the role of geodiversity in conservation. Location Subtropical forests spanning ~10° latitude in Southwestern China. Methods We conducted a large‐scale vegetation survey across 60 forest plots on parallel limestone (karst) and clastic (non‐karst) bedrocks recording over 17,000 individuals belonging to 654 woody species. We analysed diversity patterns in relation to latitude, climate, soil physicochemical properties and bedrock composition using structural equation modelling and linear mixed models. Results Despite similar climatic variation, karst forests exhibited higher topsoil Ca and Mg concentrations (SoilPC1) than non‐karst forests. Together with shallower soils and lower SiO 2 contents at low latitudes, elevated SoilPC1 was associated with lower species richness, consistent with the ~20% lower richness in karst forests. We found a positive effect of climate on richness (0.22), while SoilPC1 exerted a stronger negative effect (−0.34). Non‐karst forests followed the traditional LDG pattern, with diversity increasing towards lower latitudes whereas it declined towards lower latitudes within karst forests, reversing the LDG trend. This divergence was associated with increasing SoilPC1 and declining soil depth and SiO 2 contents towards low‐latitude karst regions. Main Conclusions Our findings provide evidence that bedrock‐driven differences in edaphic conditions between karst and non‐karst systems fundamentally regulate plant diversity reshaping LDG patterns. This advances the floristic geo‐lithology hypothesis and calls for integrating geodiversity into conservation frameworks. Given the ecological sensitivity and global extent of karst ecosystems, understanding bedrock–climate interactions is critical for conservation planning.