Study On The Intraspecific Leaf Functional Traits Of Common Species Loropetalum Chinense And Vaccinium Carlesii In Fragmented Habitats

Intraspecific trait variations contribute to the adaptability of plant species to the heterogeneous environments,which can affect population regeneration,community assembly and ecosystem processes.In this study,we focused on two common native woody plant species,Loropetalum chinense and Vaccinium carlesii in the fragmented habitats of Thousand Island Lake(TIL),to explore the intraspecific variations of leaf functional traits and environmental drivers of such variations.We also investigated the relationships between intraspecific trait shifts and herbivory,as well as leaf longevity.Here,we measured leaf functional traits: leaf area,specific leaf area,chlorophyll concentration,leaf dry matter content,leaf total carbon content,leaf total nitrogen content,leaf total phosphorus content,and leaf carbon to nitrogen ratio of 400 mature trees and 400 seedlings of the two species,as well as herbivory and leaf longevity of each seedling.Meanwhile,we measured abiotic factors including community canopy closure,soil maximum water retaining capacity,soil total carbon,nitrogen and phosphorus content within study sites.Using the correlation test,principal component analysis,linear mixed effects models,piecewise structural equation model,etc.,we found that:(1)The coefficient of variations of leaf functional traits were different across traits.Specifically,functional traits related to photosynthesis(i.e.specific leaf area,chlorophyll concentration,etc.)had greater intraspecific variations,while the functional traits related to structure and defence(i.e.leaf dry matter content,leaf total carbon content,etc.)had less intraspecific variations.(2)Within the same species,most of the functional traits showed larger variations within the seedlings compared to that within the mature trees.(3)Leaf economics spectrum existed within seedlings of the two common native species Loropetalum chinense and Vaccinium carlesii in the fragmented habitats of TIL,which was reflected in principal component 1 and indicated the maximum photosynthetic efficiency.(4)Habitat fragmentation could affect intraspecific leaf functional traits by altering habitat conditions.Habitat fragmentation initiated the shift of leaf functional traits of seedlings towards the ‘slow' end of leaf economics spectrum.(5)Specific leaf area was positively correlated with leaf herbivory to some extent.However,among different habitats,leaf herbivory did not decrease with the leaf functional traits of seedlings tending to be more defensive.(6)Seedlings adopting the slower resource-use strategy did not have longer leaf longevity.Leaf longevity increased significantly with the increase of community canopy closure.This study showed that common species in fragmented habitats may adapt to the changing environment by adopting different resource-use strategies through adjusting their intraspecific leaf functional traits in different habitats and at different ontogenetic stages.This research can enrich the theory of plant leaf economics spectrum to some extent,and indicate that the effects of variations in leaf functional traits within species should be considered when studying community assembly and biodiversity maintenance mechanisms in fragmented habitats.