Study On Community Characteristics Of Evergreen Broad-leaved Forest In Zhoushan Islands

Evergreen broad-leaved forest is a zonal forest vegetation type in the middle subtropical zone.It has attracted much attention for its rich biological resources,rich species diversity and huge ecological functions.There are many islands in East China,and the evergreen broad-leaved forest in coastal areas has unique population composition,appearance structure and spatial distribution.Taking Zhoushan Islands as an example,the evergreen broad-leaved forest on the island belongs to the forest areas of Castanopsis eyrei and Schima superba in the northern sub zone of subtropical evergreen broad-leaved forest,while there are few Castanopsis eyrei and Schima superba forests on the island,including Machilus thunbergii,Cinnamomum japonicum Quercus glauc and other evergreen broad-leaved populations are the main species.The communities with these plants as the dominant species constitute the unique and representative typical plant communities on the island.Moreover,Zhoushan Islands are rich in natural environmental resources,less disturbed by human beings,and the vegetation on the island is intact,representative and typical.Therefore,the community characteristics of evergreen broad-leaved forest on Zhoushan Islands are studied,It provides a reference for the restoration of zonal vegetation landscape and the construction of urban green space in the coastal area of East China.The results show that:(1)Zhoushan Islands is rich in plant species.The evergreen broad-leaved forest types are mainly Castanopsis sclerophylla forest,Putuo camphor forest,Hongnan forest,Putuo camphor+Hongnan forest,Cyclobalanopsis glabra forest,Cyclobala-nopsis glaber+Lithocarpus glaber forest.The diversity index characteristics of the six types of evergreen broad-leaved forest are different due to the influence of external environment and internal interspecific competition relationship,The communities with greater human disturbance showed lower species richness,while the commun-ities with fierce interspecific competition showed lower community stability.(2)According to the age class structure distribution,static life table drawing and survival curve drawing,it is found that the development trends of different types of populations in the tree layer of evergreen broad-leaved forest have their own characteristics.The age class differentiation of evergreen dominant species is more and continuous,and the population shows a high survival rate in the low age class.With the increase of age class,the viability decreases and the mortality increases,reaching a certain age class,the population tends to be stable,and the population development trend shows a stable growth state on the whole;The age class distribution of positive deciduous species in the community is intermittent,most of them are older individuals,lack of younger and newer individuals,and the population shows a declining trend.(3)The calculation results of Levins niche width and Shannon Wiener niche width of various groups are basically consistent.The niche width of evergreen broad-leaved dominant species such as Castanopsis eyrei,Phoebe,Putuo camphor,Cyclobalanopsis glauca and Lithocarpus oak is the largest,showing strong ability to utilize environmental resources,which is suitable for species selection of zonal vegetation restoration in coastal areas of East China;The middle and lower vegetation,such as Eurya muricata,Ardisia crenata,Quercus serrata,Styrax confus,Camellia japonica,Ficus pandurata and Symplocos lucida,has a large niche width and is suitable for the construction of understory vegetation landscape.According to the calculation results of pianka niche overlap,the populations with large niche width often have large niche overlap.Combined with the interspecific connection coefficient,the species pairs with large niche overlap are accompanied by high positive connection,such as Hongnan Putuo camphor,Hongnan cinnabar root,Putuo camphor Eurya,Cyclobalanopsis glauca-Quercus.(4)The current situation of evergreen broad-leaved forest is mainly divided into three types:first,the community composition structure is complex and the succession stage is high;Second.Mixed forest with small community size,scattered distribution or low dominance of evergreen broad-leaved trees;Third,the degraded plantation of evergreen broad-leaved trees with simple structure and single species.Based on the study of the community characteristics of evergreen broad-leaved forest in Zhoushan Islands,corresponding protection suggestions were put forward for the protection of evergreen broad-leaved forest in different current situations.