Effects Of Fragmentation On Plant And Animal Communities And Animal-mediated Seed Dispersal In Urban Forests

Forest fragmentation is a process that large and continuous forests in the natural landscape are converted into small and isolated patches.Anthropogenic disturbances have rapidly accelerated forest fragmentation globally,and the phenomenon of forest fragmentation is extremely serious in many areas.Fragmentation changes the habitat environment and has a negative impact on organisms,results in gradual degradation of forests,decreases self-restoration of the entire community,and declines ecosystem function.However,the effects of forest fragmentation on species interaction and plant-animal functional relationships are not well studied at community level.Here,I studied the plant and animal diversity,species-patch networks and animal-mediated seed dispersal in urban forests of Wuhan City,and the objective of this study is to know the effects of forest fragmentation on biotic communities and interspecific relationships in urban ecosystems under the conditions of rapid urbanization.We selected 10 forest patches with different sizes in Wuhan City,and investigated species of plants(woody plants,seedlings and herbaceous plant)and animals(birds and mammals)in the forest patches,constructed and analyzed the structure of the species-patch networks.We researched the effects of fragmentation on animal-mediated seed dispersal by using Quercus variabilis acorns.The questions involved mainly include:(1)What is the impact of fragmentation on the composition and diversity of plant community and the structure of plant-patch networks in urban forest?(2)What is the impact of fragmentation on the composition and diversity of animal community and the structure of animal-patch networks in urban forest?(3)What is the impact of fragmentation on animal-mediated seed dispersal of Q.variabilis acorns?The results showed that:(1)99 species of woody plants,93 species of seedlings and 91 species of herbaceous plants were found in the 10 forests.The common tree was Pinus massoniana,the common seedling was Cinnamomum camphora and the common herb was Trachelospermum jasminoides.Forest fragmentation had a negative impact on the richness of woody plants,the richness and diversity of seedlings,while herbaceous plants were less affected by fragmentation.The woody plant-patch network and the seedling-patch network showed low connectance,high nestedness and moderate modularity,and the herbaceous plant-patch network showed low connectance,moderate nestedness and low modularity.Forest fragmentation mainly affected woody plant-patch network and reduced its nestedness and stability.(2)A total of 10 species of mammals and 62 species of birds were found in the survey.Meles meles was the common mammal and Garrulus glandarius was the common bird.Forest fragmentation had a negative impact on the richness,individual number and diversity of mammals,but the richness,individual number and diversity of birds had no direct correlation with forest area.The mammal-patch network showed moderate connectance,high nestedness and low modularity,and the bird-patch network showed low connectance,high nestedness and low modularity.The effects of fragmentation on the mammal-patch network were obvious,and nestedness and stability of the network decreased in the small forest patches.(3)Q.variabilis is a common tree in Wuhan City,its acorns were dispersed by G.glandarius,Niviventer confucianus,Apodemus agrarius and A.draco,and the main predators were M.meles,Sus scrofa and Lepus sinensis.The number of predators of Q.variabilis acorns was not related to the forest size,and the number of dispersers decreased with the decrease of forest area,especially the rodents.In addition,forest fragmentation affected the dispersal of acorns,a higher proportion of acorns were dispersed in the large patches,while in the small patches,only a few acorns were removed by animals,the decrease in the number of rodent populations in small patches may be the key reason that hindered of acorn dispersal.In this study,the potential impacts of fragmentation on urban forest ecosystems were systematically explored from the perspectives of the diversity of plant and animal,characteristics of species-patch network and animal-seed interaction.Our results are helpful to improve the understanding of fragmentation and provide reference for urban green space management and ecological civilization construction.