Spatial distribution and association patterns in a tropical evergreen broad-leaved forest of north-central Vietnam

Abstract

Questions What are the prevailing types of intraspecific spatial distributions and interspecific association patterns at species and life stage levels of trees in a tropical rain forest? Which ecological processes could structure these patterns? Possible processes include dispersal limitation, self‐thinning, facilitation and competition between species and life stages. Location A tropical broad‐leaved forest in north‐central Vietnam. Methods We used univariate and bivariate pair‐correlation functions to investigate the spatial distribution and association patterns of 18 abundant tree species. To disentangle first‐ and second‐order effects, we used a scale separation approach with the heterogeneous Poisson process as null model. Results (1) Sixteen of 18 species had aggregated patterns at various scales and regardless of their abundance. (2) Significant and aggregated patterns were found in 64% of all specific life stages. (3) At scales up to 15 m, 12.4% species pairs showed significant associations, among that 71% were spatial attractions, 5% were spatial repulsions and 24% were non‐essential interactions. (4) In different life stage associations, attractions (81%) predominated over repulsions (19%) at small scales of up to 15 m. Conclusions Our findings provide evidence that dispersal limitation may regulate the spatial patterns of tree species. Moreover, positive spatial associations between tree species and life stages suggest the presence of species herd protection and/or facilitation in this forest stand, while the persistence of intraspecific aggregation through life stages suggests a very late onset or even absence of self‐thinning. Habitat heterogeneity plays an important role for species distribution patterns, and the spatial segregation occurs at a scale around 15 m in this forest.