Species prefer to shifting niche positions rather than expanding niche breadth to adapt to the heterogeneous karst forests

The interspecific variations of plant functional traits can characterize the niche positions of species within communities, while the intraspecific variations can accurately display the species' niche breadth. Revealing relative contributions of intra- and interspecific variations to plant functional community structure is crucial in understanding how the species coexist together, especially in species-diverse ecosystems. To explore how the intra- and interspecific variations of plant functional traits change along the successional pathway in heterogeneous conditions, we established a series of plots and measured main plant functional traits along the natural regeneration in karst forest ecosystems. By quantifying the intra- and interspecific variations of plant functional traits, we found that the changes in intraspecific variations were relatively lower compared to changes in interspecific variations throughout the natural regeneration. Further analysis showed that the community spatial structure contributed more to the intraspecific variations of plant functional traits, while the soil physicochemical properties contributed more to interspecific variations. Our study suggested that tree species might tend to narrow their niche and change the positions to release the niche overlap when faced with heterogeneous habitat conditions.