The Study On Secondary Forest Restoration Model And Influence Mechanism In Southern Hilly Red Soil Region

Forest vegetation restoration has become a priority to solve global environmental problems.The hilly red soil region in southern China breeds the largest and most typical subtropical evergreen broad-leaved forest in the world.However,due to long-term human activities,the original vegetation is almost exhausted.With the implementation of a number of national forestry ecological projects,the vegetation in the region has been rapidly restored,and the secondary forest has become the main body of the current vegetation.However,the changes of species composition,structure and function of secondary forest community and their influencing factors are not clear.This paper takes the secondary forest in the ecological "green-core" area of Changzhutan urban cluster as the research object,and uses the typical sample method to carry out the quadrat survey,based on 115 20 m × 30 m The results showed that:(1)the evolution pattern of species composition and structure in the process of secondary forest restoration;(2)the restoration process of ecosystem functions such as community biomass and soil nutrients;(3)the main environmental factors affecting the structure and function in the process of secondary forest restoration.The main results are as follows:(1)The secondary forest can be roughly divided into five recovery stages:early recovery stage(scrub),pre-succession forest,med-succession forest,sub-climax forest,climax forest.The species composition of the community in each stage is obviously different.The scrub stage is composed of low evergreen or deciduous shrubs.The deciduous broad-leaved trees are mainly in the pre-succession forest stage,and conifers,deciduous broad-leaved trees and light loving evergreen broad-leaved trees are mainly in the med-succession forest stage.The sub-climax forest community is composed of evergreen broad-leaved trees and climax community species,and the climax forest is composed of climax species.(2)The vegetation restoration of secondary forest is nonlinear and multi-path,and the constructive species show a trend from light preference to shade tolerance.The specific performance is that the starting point of restoration is diverse,and communities with different restoration status such as shrub,deciduous broad-leaved forest and coniferous forest can be used as the starting point of restoration;the restoration paths are diverse,and the community types with different starting points can be transformed into each other without strict boundaries,for example,coniferous forest and deciduous broad-leaved forest can be transformed into evergreen broad-leaved forest;there is a phenomenon of disturbance recovery to the disturbance climax community,such as Cinnamomum camphora forest can grow directly from bare land and exist stably for a long time.(3)In the process of secondary forest restoration,the species richness changed little,and the woody plant species richness decreased slightly;the vertical space of the community increased gradually,and the hierarchy became more complex;the plant density of the groups with different survival strategies varied greatly,which generally reflected the trend of first increasing and then decreasing;generally,about 20%of the species were renewed in each restoration stage,and the regeneration of the group species was more important The ability of recovery increased with the degree of recovery.Generally speaking,secondary forest restoration makes its community structure more complex and stable.(4)The biomass increased gradually with the recovery process,but during the replacement of constructive species,the biomass may decrease in a period of time,and the biomass at the climax forest stage was much higher than that at other stages.During the recovery process,the soil water holding capacity gradually increased,the soil bulk density did not change significantly,the contents of total carbon and total nitrogen increased significantly,and the content of total phosphorus decreased.(5)The 11 selected environmental factors accounted for 21.92%of the variation of secondary forest restoration model.Slope position,slope,disturbance intensity and so on were the main environmental factors affecting secondary forest vegetation restoration.These factors could better explain the changes of community composition and structure in the early stage of restoration,but they were not strong in the middle and late stages of restoration,and they tended to have no real decision to restrict vegetation restoration Qualitative factors,propagation,colonization and other stochastic processes dominate vegetation restoration.This paper studies quantitatively the changes of species,structure and function in the process of secondary forest restoration in the hilly red soil region of southern China,and explores the environmental factors affecting vegetation restoration,which can provide a scientific basis for regional vegetation restoration and precise improvement of secondary forest quality.The "interspecific association—restoration coefficient method" used in the division of restoration stage is of great significance for the division of restoration stage or succession stage It has a certain reference value.