Fire and Landscape Configuration Shape Forest Futures: Direct and Indirect Drivers of Seedling Diversity in a Human-Modified Tropical Rainforest

Abstract Context The seedling community plays a crucial role in forest regeneration within fragmented rainforests. The characteristics of patches, including their size, shape, vegetation, and disturbance, as well as the composition and configuration of the surrounding landscape, have a significant effect on seedling communities. However, the response of seedling communities to patch and landscape structures varies, and the direct and indirect effects on seedling composition and diversity remain unclear. Objectives Considering the hierarchical relationship between landscapes, patches, and seedlings, we investigated the direct and indirect effects of patch and landscape structures on seedling communities across 16 forest patches in a highly fragmented rainforest in southeastern Mexico. Methods We adopted a multi-scale approach to assess how landscape composition and configuration influence patch structure. Subsequently, piecewise structural equation models were used to evaluate the direct and indirect (cascading) effects of patch and landscape structures on seedling abundance, composition, and α- and β-diversity. Results Our findings revealed that fire disturbance had cascading negative effects on seedling composition and β-diversity, increasing the abundance of light-demanding seedlings and thereby promoting the growth of early successional species. By contrast, patch aggregation had a cascading positive effect on seedling richness by enhancing the abundance of shade-tolerant seedlings, thereby supporting seed dispersal. Conclusions These results support the notion that the effects of patch disturbance and landscape configuration patterns on biodiversity are more pronounced in highly fragmented landscapes where spatial configuration can play a key role in enhancing regeneration resilience.