| Pingtan Island is the fifth largest island in China and the largest island in Fujian Province.Its development goal is to become an ecological and livable international tourism island on the west coast of the straits.However,the large-scale development and construction of cities in recent years have made a profound impact on the ecological environment.As an island with a poor ecological foundation,Pingtan Island lacks biodiversity and has poor ecosystem control capabilities.The invasion of alien species will cause great harm to its ecosystem.In this study,a line survey and a typical sample survey were used to study the community ecology of alien plants communities under different living conditions in Pingtan Island.This paper discusses the community status and habitat adaptability from three aspects of flora,species diversity and community classification,so as to judge the invasive nature of alien species,study the invasive status of alien herbs in Pingtan Island,and evaluate their ecological impact.This practice not only enriched the data of alien plants on the island,but also effectively improved the ability to prevent and control the invasion of alien plants and promote the healthy development of the island ecological environment.Specific research results are as follows:(1)Flora of alien herbs on Pingtan Island.(i)A total of 407 species of herbs were investigated and collected,belonging to 285 genera of 73 families,among which there were 123 species of alien herbs,including 41 families,102 genera.The characteristic of family and genus composition is that there are more single genera,single species and few species in the genus.(ii)Among the areal types of families and genera,44.4% and14.2% are mainly distributed in the world,47.6% and 61.7% in the tropical families and genera,8.0% and 23.7% in the temperate families and genera.It can be seen that tropical families: temperate families ?6:1;Tropical genus: temperate genus ? 3:1.The geographical composition of the flora was in the lead of tropical plants in both family and genus,which indicated that the tropical nature of the flora of alien herbs was more significant.(iii)The proportion of annual and biennial alien herbs was 46.3%,and the proportion of perennial alien herbs was 41.5%,they are very similar.However,the species of herbaceous climber and subshrubby herbs were less,accounting for 8.9% and 3.3% respectively.(2)Characteristics of alien herbs community in Pingtan Island.(i)According to the records of the sample survey,there are 210 species of herbs in the island,belonging to 164 genera of 65 families,among which46 species belong to 40 genera of 22 families of alien herbs.The species with the most important value is Bidens pilosa var.radiata(15.77),followed by Aster subulatus(7.68)and Praxelis clematidea(4.27).Fromthe distribution frequency,it can be seen that the limited number of species has an absolute advantage.There are 9 species in a wide range of habitats which includes 4 alien herbs;there are 30 species in a wide range of areas which includes 12 alien herbs.(ii)Studying the species diversity of alien herb communities in different habitats and areas,the results show that : From the perspective of species richness,in different ecological environments,the roadside wasteland was higher(17.81)and the front and back of the house was lower(11.37).Among the areas,Jinjing Area was higher(21.03)and Junshan Area was lower(13.53).According to the analysis of Simpson index and Shannon-Wiener index,in different ecological environments,the front and back of the house were better(1.973,0.826,respectively),and the flowerbed lawn was worse(1.637,0.706,respectively).Among the areas,the Jinjing area was better(1.855,0.786,respectively)and the Haitan area was worse(1.730,0.742,respectively).(3)Determination of the invasiveness of alien herbs on Pingtan Island.(i)By constructing an invasive evaluation system of island alien herbs,46 invasive herbs in alien herb community were evaluated.Eight items including origin,growth status,invasion route,etc.were selected as evaluation indicators,and the scores of each evaluation indicator of each species were counted to determine the size of invasiveness.According to this,four invasion levels were divided: score ?30,defined as grade Imalignant invasion,30?25,defined as grade II severe invasion,25?20,defined as grade III local invasion,and < 20,defined as grade IV general invasion.Among them,there is one kind of Class I malignant invasion,namely Bidens pilosa var.radiata;there are 9 kinds of Class II serious invasions,such as Conyza canadensis and Aster subulatus;there are 25 kinds of Class II serious invasions,such as Amaranthus viridis and Amaranthus lividus;there are 11 kinds of local invasions of grade III,such as Sesbania cannabina and Talinum paniculatum.(ii)By analyzing the invasion status of 46 kinds of alien herbs,this paper puts forward the prevention and control strategies from three aspects: the key family,the main ecological environment and the invasion route. |
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