Studies On Species Diversity Of Lycophytes And Ferns In Wuzhi Mountain National Nature Reserve,Hainan

Wuzhi Mountain National Nature Reserve,is located in the hinterland of south central Hainan.Flora and ecological characteristics of lycophytes and ferns had not been acquainted.Using the methods of field route investigations,specimens collection and identifiction,and literatures review,floristic composition,floristic geographical elements and floristic relationship with several other areas were studied.In addition,based on the field quadrate investigations,the importance values,niche characteristics,and altitudinal gradient pattern of a and ? diversity of the main lycophytes and ferns in herbaceous layer were also studied.The following results have been obtained in this research:(1)Lycophytes and ferns flora of it composes of 290 species(including subspecies and variety)of 95 genera in 28 families.The dominant families are Polypodiaceae,Pteridaceae,Dryopteridaceae,Athyriaceae,Aspleniaceae,and Thelypteridaceae.Among its floristic elements,the tropical distribution elements of lycophytes and ferns families,genera and species are account for 100%,91.2%,84.4%of the total in Wuzhi Mountain(Cosmopolitan excluded),so it shows that this lycophytes and ferns flora has stronger tropical nature.At the level of species,the tropical Asia element is dominant,thus it indicates that the Wuzhi Mountain fern flora has close affinity with the Asian tropical flora,especially the Indochina flora.In additon,this flora also has some East Asia species and a few local endemic species.Compared with the flora of seven neighboring areas,the Wuzhi Mountain fern flora is much more closely allied to Yinggeling,following by Jianfengling,Yunkai Shan and Ganjiangyuan,while it has a weak relationship with Dulongjiang and Mayanghe.Nine fern species are under Class ? National Protection,and four species are critically endangered in the area.(2)The genus Petrosavia Becc.,represented by Petrosavia sakuraii(Makino)J.J.Sm.ex Steenis and two ferns,namely Asplenium ×xinyiense Ching&S.H.Wu(Aspleniaceae)Metathelypteris uraiensis(Rosenst.)Ching(Thelypteridaceae),are recorded for the first time from Hainan Island.(3)Selaginella monospora,Selaginella picta,Selaginella scabrifolia,Plagiogyria japonica and Dryopteris cyclopeltidiformis have higher importance value than other lycophytes and ferns in herbaceous layer.Niche breadth and niche overlapping of 20 main lycophytes and ferns populations in herbaceous layer were studied.Selaginella monospora,Selaginella scabrifolia,Asplenium normale,Diplazium viridescens and Arachniodes cavaleriei have the largest niche breadth of the 20 main lycophytes and ferns.These five species have high adaptability to the environment and competition for the resources in the community.The species which have both low niche breadth value and low importance value are in need of more attention and conservation.In general,the niche overlap value between the main lycophytes and ferns populations in Wuzhi Mountain is relatively small,so the niche differentiation is obvious,and the community is in a relatively stable state.For the better protection and propagation of these lycophytes and ferns in future,we should take measures to prevent their habitat from deteriorating and being destroyed.(4)Species richness of lycophytes and ferns in herbaceous layer declines with altitude,and the maximum value of species richness index appears at 750?800m above sea level and 900-100m above sea level.The three a diversity indices increase to the peak value first,and then decrease to the lowest value,and then increase slightly.The maximum value of a diversity index appears at 900?1000m above sea level.The Cody ? diversity index is highest in the low elevation(700?1000m),because of the high human disturbance and habitat heterogeneity in the lower elevation area.The value of Cody is higher in the area close to the top of the mountain(above 1700m),which reflects the complex and diverse habitats of the summit.The Cody values of 1300?1700 m above sea level are relatively small and gentle,which reflects the higher uniformity of habitat in this area,and the distribution of lycophytes and ferns are continuous.