Studies On Flora And Geographic Distribution Of Bryophytes In Ma'an Archipelago,Zhoushan,Zhejiang

Ma'an archipelago is located in the south-east of Yangtze River,north-east of the Zhoushan islands and east of the Shengsi archipelago?N30°41'³0°51',E122°35'¹22°49'?.The archipelago is generally northwest-southeast dispersed arrangement,the length is 28 km from east to west and the width is 22.3 km from north to south.The six islands as West Lvhua Island,East Lvhua Island,Huaniao Mountain Island,Pishang Mountain Island,Gouqi Island and Shengshan Island whose areas more than 1 km² distribute in an arc shape from southwest to northeast and then form a perfect harbor against the north wind.Through ecological investigation,2228 specimens of bryophytes were collected from 22 islands of Ma'an archipelago.After the identification of specimens combined with the ecological data,quantitative classification,sorting and other statistical methods,species diversities,floristic elements,and impact factors on bryophytes were studied.The main results were as follows:1.A total 197 species of bryophytes belonging to 76 genera and 34 families in Ma'an archipelago were identified.Among these,24 species,16 genera and 8 families were liverworts,1 species,1 genera and 1 family was hornworts,while 172 species,59 genera and 25 families are mosses.2.Pottiaceae,Bryaceae,Brachytheciaceae,Fissidentaceae,Thuidiaceae,Hypnaceae,Mniaceae,Bartramiaceae,Funariaceae,Leucobryaceae,Lophocoleaceae and Lejeuneaceae were dominant families of bryophytes which covered 155 species totally in Ma'an archipelago.Bryum,Brachythecium,Fissidens,Eurhynchium,Hypnum,Philonotis,Didymodon,Trichostomum and Pohlia were dominant genera and included 84 species.The dominant 12 families and 9 genera accounted for78.68%and 42.64%of the total species respectively.3.The ecological types of bryophytes in Ma'an archipelago were diverse.According to the investigation,the habitat type frequencies from high to low were on soils,soil over stones,on stones,sandy soils,on trees,on walls.Among them,the highest was on soils,accounting for 58.17%of all collected specimens,followed by soil over stones and on stones,which accounted for 19.48%and 13.64%of total specimens respectively,on walls was the least,only accounting for 1.35%.4.The geographic element of the bryoflora in Ma'an archipelago could be divided into 8 types,cosmopolitan element,pantropic element,old world tropical element,north temperate element,East Asia-North America disjunctive element,old world temperate element,East Asia element and Endemic to China.Except the cosmopolitan element,the dominant geographic element was north temperate element?29.61%?and East Asia element?26.26%?.5.According to the analysis of 22 islands in Ma'an archipelago,the number of bryophytes ranged from 104 species to 3 species,Gouqi Island contained the most bryophytes among the total 22 islands?104 species?.The bryophytes of Shengshan Island?99 species?and Huaniao Mountain Island?103 species?were similar to Gouqi Island.The minimum number of bryophytes?3 species?were on Qiuzi Mountain Island and Ma'an Mountain Island.Curve-Expert 1.4 and multivariate data sorting analysis software Canoco 5.0 were used to analyze and concluded that the number of bryophytes was positively related to the population,area,frequency of traffic,length of coastline,vegetation coverage,building density and highest altitude.Among these factors,the population,the highest altitude,the area,and the frequency of traffic had a greater influence on the distribution of bryophytes,while the number of bryophytes had a negative correlation with the proportion of exposed rocks.6.The number of bryophytes?Y?in Ma'an archipelago increased with the increase of island area?X₁?,population?X₂?,highest altitude?X₃?,coastline length?X₄?,vegetation coverage?X₅?,building density?X₇?and the frequency of traffic?X₈?.Their relationships could be described by the following functions:Y=43.810*X₁^0.537?P<0.001??Y=11.001*X₂^0.253?P<0.001??Y=0.0241*X₃^1.538?P<0.001??Y=0.0278*X₄^0.829?P<0.001??Y=0.00519*X₅^1.619?P<0.001??Y=10.552*X₇^0.675?P<0.001??Y=4.975*X₈^1.891;The relationship between the number of bryophytes and area was consistent with the Theory of Island Biogeography.