Dominant species and dispersal limitation regulate tree species distributions in a 20‐ha plot in Xishuangbanna, southwest China

Abstract

Habitat heterogeneity and dispersal limitation are widely considered to be the two major mechanisms in determining tree species distributions. However, few studies have quantifi ed the relative importance of these two mechanisms at diff erent life stages of trees. Moreover, rigorous quantifi cation of the eff ects of dominant tree species in determining species distributions has seldom been explored. In the present study, we tested the hypothesis that the distribution of tree species is regulated by diff erent mechanisms at diff erent life history stages. In particular, we hypothesised that dispersal limitation regulates the distribution of trees at early life stages and that environmental factors control the distribution of trees as they grow, because of niche diff erentiation resulting from environmental fi ltering. To test this, trees in 400-m 2 quadrats in a 20-ha plot in Xishuangbanna, southwest China were grouped into four classes on the basis of the diameter at breast height (DBH) that roughly represent diff erent stages in the life history of trees. A neighbourhood index was computed to represent a neutral spatial autocorrelation eff ect. We used both biotic (dominant species) and abiotic (topography and soil) predictor variables to model the distribution of each target species while controlling for spatial autocorrelation within each of the DBH classes. To determine which factors played the largest role in regulating target species distribution, the simulated annealing method was used in model selection based on Akaike information criterion (AIC) values. Th e results showed that the relative importance of neutral and niche processes in regulating species distribution varied across life stages. Th e neutral neighbourhood index played the most important role in determining the distributions of small trees (1 cm Յ DBH Յ 10 cm), and dominant species, as biotic environmental predictor variables, were the next most important regulators for trees of this size. Environmental predictor variables played the most important role in determining the distributions of large trees (10 cm Յ DBH). Th is fi nding builds on previous research into the relative importance of neutral and niche processes in determining species distributions regardless of life stages or DBH classes.

Size-Class Effect Contributes to Tree Species Assembly through Influencing Dispersal in Tropical Forests

“…This pattern is consistent with a recent finding that the contributions of neutral processes to tree species survival shift with the change from juvenile to reproductive stages at the BCI plot [10]. At the Bubeng plot, it has once been verified, using regression and ordination methods on the tree lattice data, that dispersal is the dominant process in shaping species’ distributions [33], [42]. At the BCI plot, Levine and Murrell [50] have suggested that dispersal is important for species’ distributions at the species level.…”

Spatial distribution of tree species in a species-rich subtropical mountain forest in central China

“…Recent studies have shown that dispersal limitation played an important role at local scales, whereas the combination of habitat heterogeneity and dispersal limitation controlled spatial patterns at regional scales (Plotkin et al 2002;Kallimanis et al 2008;Shen et al 2009;Lin et al 2011;Cheng et al 2012;Hu et al 2012). One study in two temperate forests suggested that the combined effects of habitat heterogeneity and internal clustering mechanisms, such as dispersal limitation, led to a good approximation of the observed species-area relationships and distance-decay curves .…”

“…Within the plot, all woody stems ≥1 cm in DBH (1.36 m were mapped, measured, identified to species, and tagged following standard field procedures (Condit 1998) For a tree with multiple stems, we computed the total DBH following Hu et al (2012). To obtain a sufficient sample size for point-pattern analyses, we chose 137 common species with no less than 25 individuals for analysis (Appendix 1).…”

Heterogeneity in soil water and light environments and dispersal limitation: what facilitates tree species coexistence in a temperate forest?

“…Hu et al (2012) found that species distribution was determined by dispersal limitation in the younger stages. However, no evidence of effective dispersal limitation was found in the present study.…”

“…Comita et al (2007) suggested that individuals in the adult tree stage more often have significant distributional correlations with specific soil moisture conditions. Hu et al (2012) further argued that the distribution of small trees is likely to be explained by dispersal limitation, whereas the distribution of adult trees is more likely to be determined by the environment. These studies postulate that the associations of mature trees with specific habitat conditions can be formed during the early life stages via differentiated growth and mortality between species (Metz 2012).…”