It is one of the major challenges in forest ecology to understand how functional differences in species traits are associated with the demographic performance of trees. We examined how diverse co-occurring tree species differ in their traits and how such differences associate with demographic rates. In particular, we focused on the sapling stage, a bottleneck of life history with higher mortality rates than later development stages, and where stronger trait-demography associations are reported.
We asked if species traits affect demographic rates of saplings in the same manner in different forests with common species using sapling census data in two forests. We applied growth and survival data of saplings in the 4 ha long-term dynamics plots, Aya and Yakushima. Sapling census quadrats were established at the corner of each subplot (10 x 10 m in Aya, 20 by 20 in Yakushima) in the 4 ha plot. We censused sapling growth and survival from 1994 to 2020 for Aya and from 2005 to 2019 for Yakushima. We also measured species traits of leaves and woods for saplings of dominant species at each site. We will discuss the trait-demography relationship based on the results of demographic models, including species traits as explanatory variables.