Abstract:

Understanding the processes underlie spatial distribution patterns of tree species is fundamental for understanding species coexistence. Tropical karst seasonal rainforests, located on the northern margin of the tropical limestone karst region of China, are very unique. The limestone karst forests in this region have shallow, calcium-rich, alkaline soils with low water holding capacity, high ratio of exposed rock, and periodic flooding. In this study, we examined the spatial distribution patterns of woody plants using a univariate pair correlation function to quantify spatial patterns of species in a fully mapped 15 ha dynamic study plot in Nonggang, Guangxi, southern China. We analyzed the relationships between species attributes and spatial distribution patterns of 160 tree species with at least one individual per hectare. The results showed that species were predominantly aggregated and that the percentage of significantly aggregated species decreased with increasing spatial scales. A total of 146 species showed aggregation patterns at the scales of 0-10 meters. Rare species were more aggregated than intermediate and abundant species, but more easily influenced by habitat heterogeneity. The aggregation intensity showed a negative relationship to mean DBH (diameter at breast height) and maximum DBH, i.e., species became more regularly spaced as species stature increased but there was no significant difference between evergreen and deciduous species. Most species showed random patterns after controlling for the effects of habitat heterogeneity. Our results partially agree with the prediction that species’ attributes influence spatial patterns following similar laws. Consequently, species attributes and habitat heterogeneity are likely the primary drivers of spatial patterns and species coexistence in natural forest communities.

Key words: spatial pattern, pair correlation function, aggregation, Nonggang Dynamics Forest Plot, Northern tropical karst seasonal rainforest