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

Abstract

We have investigated the processes of community assembly using size classes of trees. Specifically our work examined (1) whether point process models incorporating an effect of size-class produce more realistic summary outcomes than do models without this effect; (2) which of three selected models incorporating, respectively environmental effects, dispersal and the joint-effect of both of these, is most useful in explaining species-area relationships (SARs) and point dispersion patterns. For this evaluation we used tree species data from the 50-ha forest dynamics plot in Barro Colorado Island, Panama and the comparable 20 ha plot at Bubeng, Southwest China. Our results demonstrated that incorporating an size-class effect dramatically improved the SAR estimation at both the plots when the dispersal only model was used. The joint effect model produced similar improvement but only for the 50-ha plot in Panama. The point patterns results were not improved by incorporation of size-class effects using any of the three models. Our results indicate that dispersal is likely to be a key process determining both SARs and point patterns. The environment-only model and joint-effects model were effective at the species level and the community level, respectively. We conclude that it is critical to use multiple summary characteristics when modelling spatial patterns at the species and community levels if a comprehensive understanding of the ecological processes that shape species’ distributions is sought; without this results may have inherent biases. By influencing dispersal, the effect of size-class contributes to species assembly and enhances our understanding of species coexistence.

The effects of habitat filtering and non‐habitat processes on species spatial distribution vary across life stages

“…We presented a brief description of the three models below. More details could be found in relevant literature (John et al., ; Shen et al., ; Lin et al., ; Wang et al., ; Hu et al., ).…”

“…Another important factor, but less studied, is the possible changes of these two mechanisms across life stages of tree species. It has increasingly been recognized that the spatial distribution of a species may vary across life stages because of the change of the performance of tree species at different ontogenetic stages (Baldeck et al., ; Shen et al., ; Zhu et al., ; Hu et al., ). For instance, the minimum light requirements of seven of the 13 species studied in Lusk et al.…”