Community Structure And Vegetation Classification Of Cupressus Funebris Forest In Hunan Province

As one of the most representative forest types in South China,Cupressus funebris forest plays an extremely important role in ecological restoration,soil and water conservation and forestry production.Hunan Province is mainly concentrated distribution of Cupressus funebris forest in China,with an area of 190000 hectares,but its species composition,community structure,distribution of various vegetation types and main environmental impact factors are not clear.Therefore,clarifying the vegetation resources situation of Cupressus funebris forest has become an urgent problem to be solved.Taking the Cupressus funebris forest in Hunan Province as the research object and based on 157 20 m × 30 m quadrat data,this paper adopts the typical sample plots for systematic investigation to study three questions as follows:(1)what is the species composition and community structure of Cupressus funebris forest in Hunan Province?(2)How to divide the vegetation types of Cupressus funebris forest in Hunan Province?(3)What is the relationship between vegetation type and environmental impact factors of Cupressus funebris forest in Hunan Province?The main results are as follows:(1)Plant diversity is relatively rich.The Cupressus funebris forest contains 497 species of vascular plants belonging to 325 genera and 120 families(including subspecies),respectively accounting for 50.00%,27.17%and 12.41%of vascular plants families,genera and species in Hunan Province.There are 37 species of ferns belonging to 24 genera and 15 families,5 species of gymnosperms belonging to 4 genera and 455 species of angiosperms belonging to 297 genera and 101 families.There are 3 dominant families including more than 20 species,namely Rosaceae,Compositae and sphenoidaceae,with a total of 83 species,accounting for 16.70%of the total species.There are 12 dominant families including more than 10 species,with a total of 195 species,accounting for 39.24%of the total species.(2)The geographical composition of flora is complex.There are 10 distribution types of seed plants at the family level.Among the 71 non-world distribution families,tropical families are the dominant(51 families),accounting for 71.83%of the non-world distribution families.There are 14 distribution types at the genus level.Among the 274 non-world distribution genera,the proportion of tropical genera(131 genera)and temperate genera(143 genera)is the same,accounting for 47.81%and 52.19%of non-world distribution genera respectively,showing the transitional floristic nature from subtropical zone to tropical zone.(3)Evergreen plants in the community have stronger growth ability.In the vertical structure of layer Ⅰ-Ⅳ,the species number of evergreen plants accounted for 49.8%,39.24%,43.33%and 66.67%respectively,while the individual number accounted for 61.06%,56.43%,85.17%and 92.00%respectively.The proportion of tree species was 33.47%,84.81%,99.67%and 100%respectively,and the proportion of tree individuals was 22.41%,92.65%,99.74%and 100%respectively.The ratio of evergreen tree individuals to deciduous tree individuals in each layer was 1.16,1.13,5.72 and 11.5 respectively.(4)The structure of diameter at breast height(DBH)and height(H)class of tree layer shows that the final succession direction of Cupressus funebris forest is evergreen broad-leaved forest or evergreen deciduous broad-leaved mixed forest.The overall DBH and H structures of all tree species are single peak,belonging to recession type.Among the top 10 tree species with the important value of tree layer,Cupressus funebris,Pinus massoniana and Melia azedarach showed unimodal decline in the structure of DBH and H class.Cunninghamia lanceolata,Liquidambar formosana,Cornus wilsoniana,Cyclobalanopsis glauca and Ligustrum lucidum showed an inverted "J" growth distribution.Loropetalum chinense showed in "L" growth.The structure of DBH and H class of Cinnamomum camphora is irregular,but it has an increasing trend as a whole.(5)Based on TWINSPAN and practical observation experience,157 Cupressus funebris forest quadrats are divided into 4 association group and 50 association,of which the Cupressus funebris association group includes 1 association,and the number of quadrats accounts for 10.19%of the total quadrats.Cupressus funebrisshrub association group includes 16 association,accounting for 31.23%of the associations.Cupressus funebris-herb association group includes 8 clusters,and the quadrat proportion is 13.38%.Cupressus funebris-shrub-herb association group includes 25 associations,accounting for 45.22%of the quadrat.(6)The differentiation of vegetation types of Cupressus funebris forest in Hunan Province is mainly due to the differences of climate factors and geographical factors on a large regional scale.The common main influencing factors of species and quadrat differentiation of tree,shrub and herb layers are climate factors and geographical factors,specifically precipitation and average temperature in July,precipitation and average temperature in January,dryness,longitude and latitude.The different main influencing factors are stand factors and habitat factors,including forest age,rock exposure and soil type.The main influencing factors of association differentiation are July precipitation and mean temperature,January precipitation and mean temperature,dryness,longitude,latitude and rock exposure.Based on the main environmental impact factors,50 associations were divided into 9 habitat preference types.This paper systematically studied the community characteristics,community types and environmental impact factors of Cupressus funebris forest in Hunan Province for the first time,and discussed the community dynamics,utilization and transformation of Cupressus funebris forest,the relationship between vegetation and environment,as well as the relevant theories of vegetation classification.The results support the theory that "vegetation should be the unity of continuity and discontinuity" and the construction of succession series vegetation classification system,and can provide scientific reference and theoretical support for the study of regional vegetation classification and succession dynamics,regional vegetation management and sustainable forest management.