Study On Community Characteristics Of Cinnamomum Japonicum Var.chenii In Zhoushan Islands

Cinnamomum japonicum var.chenii,a rare tree species,was mainly distributed in Zhoushan islands.C.japonicum var.chenii community was one of main community types of zonal evergreen broadleaved forest in the islands of Zhejiang Province.However,little was known about this community due to lack of comprehensive investigation.A 1 hm2 C.japonicum var.chenii community fixed plot was established in Zhoushan islands.In the plot,all woody species at least 5cm in diameter at breast height were mapped,tagged,and identified to species,and their geographic coordinates were recorded following a standard field protocol.The niche characteristics and interspecific relationships of dominant species,species and functional diversity,community structure,floral characteristics and species composition were analysed.Draw the following conclusions:(1)The characteristics of structure and flora of C.japonicum var.chenii community.The results showed that there were 3122 genotype individuals,belonging to 34 species,33 genera,and 23 families.The flora displayed an apparent tropical characteristic,and there was a transitional characteristic from tropical floristic to temperate floristic element.The statistics of important value showed that Ficus erecta,Eurya japonica,Mallotus japonicus,Litsea coreana var.sinensis,Machilus thunbergii,Eurya emarginata,Pittosporum tobira,Dalbergia hupeana,C.japonicum var.chenii and Celtis sinensis were dominant species.As a whole,the distribution of size class of woody species in C.japonicum var.chenii community appeared as reverse “J shape”.(2)The species and functional diversity of C.japonicum var.chenii community.Shannon-Wiener index,Simpson index and Pielou evenness index of M.thunbergii community was 2.524,0.891,0.716.The major life form were deciduous arbor species and evergreen shrub species for adapting to strong wind,drought and barren environment.The major leaf-size class of community plants were small and medium leaves.The major flowering time of community plants were summer and spring.The major fruit type of community plants was drupes.(3)The distribution pattern and niche of dominant populations of C.japonicum var.chenii community.Distribution pattern of dominant populations were clumped.Clump intensity from high to low,in order was Celtis sinensis,Dalbergia hupeana,C.japonicum var.chenii,Pittosporum tobira,Eurya japonica,Mallotus japonicus,Eurya emarginata,Ficus erecta,Litsea coreana var.sinensis and Machilus thunbergii.The niche breadth of Litsea coreana var.sinensis,Machilus thunbergii,Mallotus japonicus were broader than other species,with Levins and Hurlbert' niche breadth values of 1.36,1.33,1.32 and 0.85,0.77,0.74,C.japonicum var.chenii had medium niche breadths,Celtis sinensis and Maclura tricuspidata had narrower niche breadths.Among the total 105 species pairs,there were 50 species pairs with niche overlap more than 0.5,accounting for 47.62% of the total pairs.Eurya japonica and Eurya emarginata had the largest niche overlap,which belonged to the same genus.C.japonicum var.chenii and Maclura tricuspidata,C.japonicum var.chenii and Ficus erecta had larger niche overlap.(4)The interspecific relationships of dominant populations of C.japonicum var.chenii community.Significantly positive correlations existed among the 15 dominant species,which suggested that the community structure was stable.The X2 test showed that among the total 105 species pairs,13 species pairs exhibited extremely significantly positive association,8 species pairs exhibited significantly positive association,3 species pairs exhibited extremely significantly negative association and 1 species pairs exhibited significantly negative association.101 species pairs did not show significant association.The X2 test and association coefficient showed that species pairs with positive association were more than that with negative association.Therefore,the interspecific association of dominant species of C.japonicum var.chenii community in Zhoushan islands was relatively loose with certain independent at low extent.The community was in the middle stage of succession.The main competition species of C.japonicum var.chenii were Maclura tricuspidata and Ficus erecta.According to above reserach results,suitable suggestions for the conservation and restoration of C.japonicum var.chenii population were proposed.