Vegetation Classification And Mapping Of Zhoushan Archipelago

Vegetation classification and mapping provide the scientific and methodological basis for understanding the mechanisms underpinning the spatial patterns of biodiversity distribution and ecosystem functionality for a given region.Globally,islands harbor unique biological resources due to the natural properties with varied isolations and sizes.Simultaneously,islands are not only the biodiversity hotspots but also the hotspots of species extinction.China is one the largest countries owning a lot of ocienic islands.Over the past 70 years,although we conducted a series of surveys on islands' plants,there are still lack of the standard and systematic methods of vegetation classification and mapping for island plants.Zhoushan archipelago is the largest islands in China,possessing plentiful endemic plant communities and rare species.Vegetation composition in Zhoushan archipelago has changed drastically by suffering a strong human disturbance pressure,including 50-years period of artificial planting for Pinus thunbergii,a 20-years of pinewood nematode invasion,land-use change,and projects of ‘move people to bigger islands' and ‘connecting bridge'.However,we still lack the biodiversity account in the archipelago based on the vegetation classification.In this study,by focusing on terrestrial natural-and semi-natural vegetations,I and laboratory members surveyed 454 vegetation plots across 52 main islands in Zhoushan archipelago,based on both the statistical sample method(Anglo-American survey)and the typical sample plot recording method(Braun-Blanquet survey).Then,by following the standard vegetation classification scheme,i.e.,first class is ecological physiognomy,second class is floristic characteristics,and third class is community age,I conducted vegetation classification by using the TWINSPAN method.Also,I analyzed community characteristics of classified associations.In addition,the plantation vegetation and aquatic vegetation were included as supplements to achive the completeness of vegetation types for Zhoushan archipelago.Finally,I mapped the current and potential vegetations at the scales of archipelago,geographic region,and individual island.The main results detailed below.The terrestrial natural-and semi-natural vegetations of Zhoushan archipelago could be divided into 9 vegetation groups based on the vegetation physiognomy,including evergreen broad-leaved forests,deciduous broad-leaved forests,mixed evergreen and deciduous broad-leaved forests,coniferous forest,mixed coniferous and broad-leaved forests,evergreen broad-leaved shrubs,deciduous broad-leaved shrubs,mixed evergreen and deciduous broad-leaved shrubs,and grass lands.By including aquatic vegetation and plantations as a whole,there were 122associations/communities based on the floristic characteristics.Further,according to stand age,there were 188 types of successional communities across the region.With the association as a basic unit,I maped the real of current vegetations for each of the scales of archipelago,geographic region,and individual island.Concerning of climate,topography,island area and isolation,and human activities,I classified three vegetation distribution zones,including evergreen broad-leaved forest zone of the southern archipelago,mixed evergreen and deciduous broad-leaved forest zone of the middle-archipelago,and deciduous broad-leaved forest zone of the northerb archipelago.In general,evergreen broad-leaved forests occupy the islands that are characterized by large area and less remotenss,wet in habitat,weak in wind,and less in human activities.Deciduous broad-leaved forests distribute on the islands that are characterized by drought habitat,high light availability,and more human activities,with more common emergence in the northern archipelogo and in the mountain foot and the perimeter of the villages of the southern archipelogo.Mixed evergreen and deciduous broad-leaved forests distribute widely across the archipelagos.Shrublands occure mostly on the mountain top and coast area of the large islands and the remoted islands,with stressful habitat condition,high degree of soil salinity and wind velocity.Grass lands often appear at the beaches,beach dikes,bare rocks,and abandoned farmlands or surrounding area of villages.Finally,through referring the zonal climax community for a specific site,I determined a classification index system for potential vegetation by simultaneously considering current vegetation distribution,climate,topography and soil information.In accordance with the principle of "phytocoenology-ecology",the first class was climate and soils,the second class was elevation,geomorphology and vegetation types,and the third calss was micro-topography and vegetation associations.Based on this hierarchical scheme,I maped the potential vegetation for each of the scales of archipelago,geographic region,and individual island,by using vegetation association as a basic component.In summary,based on the detailed vegetation survey,this thesis completedly built up a systematic diversity account of vegetation associations,and produced a detailed map for each of the current and potential vegetation,across the scales of archipelago,geographic region and individual island of Zhoushan archipelago.The novety of this classification scheme is comprehensive consideration of the nature of secondary vegetation and the naturalized characteristics of plantation forests,as well as successional dynamics forested communities.This study is beneficial to facilitated the research of vegetation classification of ocienic islands.The current vegetation maps provide a fundamental support for the conservation and management of island biodiversity.The potential vegetation maps should have a meaningful application for guiding the effecitive vegetation restoration by targeting the specific habit conditions and vegetation properties in Zhoushan archipelago.