Leaf traits and persistence of relict and endangered tree species in a rare plant community

The rare plant communities, located in Houhe Nature Reserve, Hubei, China, are remnant evergreen and deciduous mixed broadleaved forest where many tree species have been identified as Tertiary relict and endangered plants and environmental conditions are typically characterised by low light and high rainfall. Knowledge of their patterns of leaf traits would contribute to our understanding of persistence of relict and endangered species. Here, we measured leaf mass per unit area (LMA), mass-based photosynthetic capacity (Amass), nitrogen content (Nmass), construction cost (CCmass) and photosynthetic nitrogen-use efficiency (PNUE) of 20 major tree species in a typical rare plant community. Correlations among leaf traits in the community were consistent with those from the global dataset, but they had lower Amass at any given Nmass and lower Amass and PNUE at any given LMA. Such results suggested the capacity and efficiency of photosynthetic gain from a unit investment in leaf tissue tend to be lower in the community. Moreover, they had lower LMA, CCmass and PNUE but higher Nmass than global broadleaved tree species. For relict and endangered species, the common limited factors (such as low light and high rainfall), similar leaf traits as coexisting deciduous non-endangered species and significant leaf trait relationships may allow them to persist in the community.