Exploring community assembly across life stages at both community and species levels in different forest types may help us fully understand community assembly. 

It is widely accepted that deterministic and neutral dispersal processes are two of the principal mechanisms driving community assembly. However, the relative importance of these ecological drivers between distinct life stages both at community and individual species levels remains poorly understood in different vegetation types. 

In a study published online in Journal of Vegetation Science, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) found that the tree communities are assembled mainly by dispersal process at community level. The relative importance of ecological processes for species distribution varied across life stages at species level, suggesting that there is ontogenetic shift of ecological processes in shaping tree distribution. 

The researchers used the homogeneous Poisson, homogeneous Thomas, inhomogeneous Poisson, and inhomogeneous Thomas point process models to predict the effect of stochastic, dispersal and/or environmental processes respectively on the distribution of trees across ontogeny in tropical, subtropical and subalpine forests. 

They found a strong signal of dispersal-driven community structures in their study plots. At community level, the results indicated that dispersal limitation was largely the primary force for the pattern of species area relationship (SAR) in all the three forests. Dispersal was the dominant mechanism underlying community assembly to a larger extent in the plots. 

"We propose that it is worthy to discern the processes driving species distribution with both community and species level summary statistics in multiple types of forests," said HU Yuehua, correspondence author of the study.