Study On Species Diversity And Community Characteristics Of Different Revegetation Stages In Guangxi Huangmian Forest Farm

Evergreen broad-leaved forest is a zonal vegetation in the subtropical region of Guangxi.Under the influence of human disturbance,the existing natural vegetation is mainly secondary forests.Analyzing the differences and dynamics of community structure and biodiversity of secondary natural forests at different succession stage is of great significance to reveal the secondary succession law of natural forests and promote the restoration of degraded vegetation.Based on the survey of secondary natural forests in Guangxi state-owned Huangmian Forest Farm at different recovery stage,and compared the 2011 survey data to analyzed and compared the differences of the species composition,floristic characters,species diversity,community characteristics,age structure at different recovery stage.The research results obtained are as follows:(1)The number of families,genera and species in the succession initial stage was higher than that in the succession middle stage.In the succession initial stage,there were 86 species of vascular plants in 47 families,72 genera,and in the succession middle stage,there were 34 families,51 genera,and 58 species.There were more deciduous tree species in the succession initial community.The communities of different succession stage were very similar in family composition.(2)The flora composition at different succession stage,both at the family and the generic level,was similar and dominated by tropical floristic elements.The number of families and genera of the pantropical distribution type was the largest.The families of tropical elements in the initial and middle stage of succession accounted for 59.57% and 67.65%,and the genera of tropical elements accounted for 77.78% and 84.31%.The proportion of families and genera of the tropical distribution type of the flora in the succession middle stage was 8.07 and 6.54 percentage points higher than that in the succession initial stage.(3)The species diversity in the succession initial stage was higher,but the Pielou index(J)of tree species composition was lower than that in the succession middle stage.The Shannon-Wiener index(H'),Simpson index(D),Pielou index(J),and Margalef index(Rl)were highest in the shrub layer at the succession initial stage,and the herb layer was lowest.The Shannon-Wiener index(H')and Simpson index(D)of the tree layer and the Pielou index(J)of the herb layer were the largest in the succession middle stage.(4)With the succession of forests,the important values of intolerant tree species such as Schima superba,Schefflera heptaphylla,Liquidambar formosana,Sapium discolor,Itea chinensis,Mallotus paniculatus becomed smaller,but the important values of the shade-tolerant species such as Cinnamomum parthenoxylon,Ardisia quinquegona,Castanopsis fargesii becomed larger.The evergreen deciduous broad-leaved mixed forest that has been restored for 45 years was in the succession initial stage,and the 120-year-old evergreen broad-leaved forest was still in the succession middle stage.The secondary forest has a slower secondary succession after being damaged,and it takes a long time to naturally recover to the climax community.(5)There were no significant differences in the diameter and height structures of the communities at different succession stages.Both communities were growing types,and the height structures were peak-shaped,with peaks at 5.0-7.5 m.By comparing the population structure of dominant tree species in different succession stages,it was found that the first four dominant tree species in the succession initial stage were pioneer trees.The natural regeneration was better of Schima superba and Schefflera heptaphylla of evergreen tree.The natural regeneration was poor of Liquidambar formosana and Sapium discolor of deciduous tree,and their populations were declining.The first four dominant tree species in the succession middle stage were all evergreen species,and the natural regeneration of Schima superba and Castanopsis fargesii was well,but Cinnamomum parthenoxylon was poor.(6)The number of species and individual density in the succession initial stage were higher than those in the succession middle stage.The individual density of communities in different succession stages increased with the increased of recovery time.The changes of average DBH and average tree height were different at different succession stages,and did not increase with the succession of the community.After excluding the effects of newly added and dead individuals,the average DBH and average tree height of the succession initial stage were higher than those of the succession middle stage.In 5 years,the average DBH and average tree height of the succession initial stage increased by 1.37 cm and 1.14 m,and the succession middle stage increased by 1.00 cm and 0.31 m.