Multi-scale Effects Of Habitat Loss And Fragmentation On Plant Species Diversity

Aim:This study tests the effects of habitat loss, fragmentation and heterogeneity on the species diversity of vascular plants in an artificial land-bridge island system, investigates if the effects of habitat loss and fragmentation differ depending on plant functional group, and explores the ecological mechanisms of species loss in the fragmented landscape on patch scale and landscape scale.Location:Thousand Island Lake (TIL), Chun'an, China.Methods:This study compiled presence/absence data of vascular plant species through comperhensive surveys of154land-bridge islands, and measured the abundance of plant species on a subset of29islands using the quadrat sampling survey used in the studies of forest dynamics. Plant species were assigned to three categories of functional groups according to growth form, shade tolerance and species occurrence. On the patch scale, we tested for relationships between island attributes and species richness, composition and nested structure using correlation analysis, multi-way ANOVA, and RDA. On the landscape scale, besides observed data, we generated two data sets using a random distribution model and species occurrence weighted random model to test the contribution of species occurrence to species diversity. We also simulated some fragmented landscapes with different patch numbers using a random sampling method. Then the landscape attributes were investigated how they affected the species richness and species-area relationship using correlation analysis and variation partition.Main results: Habitat loss and fragmentation have different influences on species diversity at different scales. At the patch scale, the loss of species richness is determined largely by area loss, but may also be affected by other patch attributes such as PAR and SI. Island isolation does not affect richness. Species composition on islands is in turn determined by spatial variables related to habitat fragmentation. Habitat loss and fragmentation respectively affect the species richness and composition, impacting the nestedness of plant communities. With respect to functional groups, our results show that shade-tolerant species are most sensitive to species fragmentation. At the landscape scale, lower patch number and habitat area both negatively relate to species richness in the landscape. Patch number also affects the SARs of highly fragmented landscapes, and enhances the rate of species loss. Interspecies divergence plays an important role in the effect of habitat fragmentation. Responses of common and rare species determine the trend of SAR respectively at different stages of post-fragmentation.