| With the development of urbanization,the nature habitat was damaged in the extent,and these damaging is more persistent than the other factors The natural remnant vegetation in city as the core of regional natural area which preserved the most zonal characteristics and there have the highest biological diversity.Jianghuai hilly mountain height above 100-300 m,and human activities is very frequently,with the acceleration of city construction in recent years,the region ecological capacity aggravated highly.While the research on the forest vegetation in the mountains region is extremely lacking of the area.Mt.Dashu is the only remnant forest mountain and an isolated island-liked hilly fragment of Hefei City,Mt.Zipeng is the eastward extension of Dabie mountain.Two of them are the ideal places for the study of characteristics and development of vegetation flora of Jianghuai hilly.Research on the regional biodiversity characteristics and differentiation pattern have an important significance on the regional forest conservation and ecosystem restoration,as well as the reconstruction of damaged nature vegetation ecosystem.In order to better understand the forest vegetation in the area,this study analylized the structure and dynamics of communities and dominant population by investigating the floristic composition,structure characteristics and diversity pattern of plant communities at different micro-landform units.It would reveal the differentiation pattern of species diversity and regeneration of vegetation in the area and clarifies the coexistence mechanisms of plant species.Thus,it would provide the evidence for vegetation conservation and restoration for damaged ecosystem.The main conclusions are as follows:A total of 508 plant species,belonging to 315 genera and 120 families were recorded in Mt.Dashu.The analysis of floristic geographical elements indicates that the flora has obviously transitional feature of the North subtropical flora.According to the comparsion analysis in terms of R/T rate,the results showed that the tropic characteristic flora of Mt.Dashu flora is 0.6429,higher than those of Yaoluoping Nature Reserve,Anhui&Mt.Huangcangyu Nature Reserve,Anhui,and lower than those of Mt.Mufu,Nanjing&Mt.Langya,Chuzhou,and is similar to those of Mt.Zijin,Nanjing,in terms of genera.Analysis of the alien invasive plants in Mt.Dashu,the most of them belonging to America area,including North Americaand South America,next is come from Europe.The dominants of the forest community are mainly of the following families:Fagaceae,Ulmaceae,Hamamelidaceae,Aceaceae and Tiliaceae ect.Deciduous broad-leaved forest is zonal vegetation of Mt.Dashu,the dominant species of the arbo layor are mainly composed of Q.chenii,Q.acutissima,Q.variabilis,Acer mono,Liquidambar formosana,Zelkova schneideriana and T.breviradiat.A.mono and T.breviradiata communities can be recognized as the climax species in the region by inferring from the community types,distribution area,community dynamics and population regeneration strategies.Dalbergia hupeana,Celtis sinensis,Pistacia chinensis and Platycarya strobilacea became the main composition of zonal vegetation due to the characteristics of pioneer species constitutes the pioneer stage of community succession.There were Q.variabilis,Q.acutissima,Q.chenii,Z.schneideriana,A.mono and T.breviradiata community corresponding to the different micro-landform unit in Mt.Dashu.Based on the permanent sample plots of the Q.variabilis community in Mt.Zipeng,there are 81 species belonging to 77 genera and 49 families;the deciduous species of Q.variabilis is the dominated species of the community.The abundance,the number of individuals over 100 were found as:Q.variabili,Symplocos paniculata,Cunninghamia lanceolata,Platycarya strobilacea.From the basal area analysis,the basal area of woody plants amounted to 20.9249 m2.hm-2.The basal area over 1 m2.hm-2 was only Q.variabilis,the basal area of which was 17.9381 m2.hm-2,account for 85.73%.The age of Q.variabilis showed that the community was in the aging stage lack of seedlings and saplings.The 16 typical plots of 4 successional communities were investigated using the method of "spatial sequence instead of time successional changes" in the deciduous broad-leaved forest of Mt.Dashu.The characteristics of the communities were determined with Margalef richness index(R),Shannon index(H),Pielou index(Jsw)and Simpson index(D).The results showed that the biodiversity index(H')of tree layers of P.massoniana coniferous forest,coniferous-broad leaf mixed forest,Q.acutissima forest was 1.9572,1.4849 and 0.7384,respectively,the species diversity decreased gradually during community succession.While that of the T.breviradiata forest was 1.6943.Species richness and species diversity of tree layer change significantly between Q.acutissima forest and other 3 community(P<0.05),the evenness change significantly between Q.acutissima forest and other 2 community(P.massoniana and T.breviradiata forest)(P<0.05).The species diversity of shrub layer in P.massoniana forest was the biggest(H'=2.1891),while that of the T.breviradiata forest was the smallest(H'=1.9463),shrub layer species diversity(H')and Pielou index(Jsw)decreased gradually along successional series(P>0.05).The evenness(Jsw)and species diversity(H')of herb layer in 4 forest were not significant different with each other 3(P>0.05).The biodiversity of the climax was not big.Except human activity,community development stage and its environment are the main driven factor for the speciecs diversity variation of commnunity succession.According to DBH frequency distribution pattern,Inverse-J type such as Z schneideriana,Q.chenii and L.formosana,the regeneration of the population present a recession tendency,they show mature and stable population from development trend.A.mono and T.breviradiata recruited through intermittent regeneration,and show sporadic type.The regeneration of Q.variabilis,P.teada and P.massion population appeared the shape of single peak type.Based on the investigation data of Q.variabilis population in Zipeng Mountain,the survival curve of Q.variabili population was Deevey-?.Two peaks of mortality rate existed in the lifespan:the 3th and 5th age class periods,the number of dynamic index(Vpi)was 0.As for Z schneideriana population in Mt.Dashu,the population grew well and was capable of keeping its population stable through seed germination.The population was in the growing and maturing stage,the population dynamic index was 2.7,the survival curve of the population trends to the type of Deevey-?.Most individuals of the T.breviradiata population concentrated in the middle and old age class,the survival curve of the population trended to the type of Deevey-?,and the dynamic index was 1.73,the regeneration mode of the population was seed germination,and there was in the lack of seedlings seriously.The survival curve trends A.mono population to the type of Deevey-?,the population dynamic index was 2.42,the regeneration was of seed generation and unstable at young stage. |
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