Comparison of woody species composition between rocky outcrops and nearby matrix vegetation on degraded karst hillslopes of Southwest China

摘要

Habitats with different features such as soil depth and soil/rock conditions can provide favorable environments for species with different requirements, while anthropogenic disturbances normally exert additional effects on species composition. However, specific studies have rarely been conducted in the degraded karst regions of Southwest China despite the high heterogeneity of karst habitats and past human disturbances. In this study, woody species richness and composition on rocky outcrops on a typical karst hillslope were investigated and compared with those of nearby matrices on shallow and rocky soil. Our results showed that matrix vegetation was more diverse in genera and species than vegetation on rocky outcrops. This might relate to the contrasting substrate features and different disturbance histories of these two habitats. Unlike the significant effect of slope on species richness of the matrix vegetation, rocky outcrops exhibited no significant differences between upper and lower slope positions, largely because their microhabitats were similar in different slope positions. Although the study area has been reforested naturally for about 30 years, woody species of the matrix vegetation were still dominated by pioneer shrub species. Rocky outcrops were dominated by late-successional tree species, which was primarily related to their isolated features and resistance to certain disturbances. Most of these late-successional species were not habitat endemics, indicating the possibility for their encroachment into surrounding the matrix. From this aspect, further studies will be necessary to identify and address the limiting factors for the encroachment of these late-successional species into the surrounding environment.