A Study Of Community Characteristics And Recovery Status Evaluation Among Different Restoration Stages Of Loropetalum Chinense Communities In Karst Area Of Lijiang River Valley

By adopting the concept of space as a substitute for time,we used conventional community survey method to study the different restoration stages of Loropetalum chinense communities which the conditions of the site are basically consistent in karst area of Lijiang River valley.We selection shrub stage,shrub to tree stage and tree stage of L.chinense communities as the object of study to conduct field investigation and indoor analysis.First,analysis dynamic changes of species composition and diversity among the different restoration stages of L.chinense communities;Construction biomass model of stumpage among the different restoration stages of L.chinense communities and analysis the biomass allocation and community structure dynamic changes of different restoration stages;Then,analysis and evaluation the characteristic of soil ecohydro-function;Finally,comprehensive evaluation the recovery mode of different restoration stages of L.chinense communities by structure restoration degree evaluation model.The results show as follows:(1)Study on the species composition and diversity shows:We recorded 81 species of vascular plants from 48 families and 67 genera in L.chinense community,and which 51 species in shrub stage,57 species in shrub to tree stage and 48 species in tree stage.The main dominant species of different restoration stages of L.chinense communities include L.chinense,Pistacia chinensis,Bauhinia championii,Alchornea trewioides,Decaspermum esquirolii and so on,and L.chinense is still edificator.Species of shrub to tree stage becomes richer,and species of tree stage becomes unitary.Shannon index and Pielou index almost the same trend changes with the development of restoration stages,shows that the Shannon index is relatively more affected by individual distribution uniformity among species of L.chinense community.With the natural restoration of L.chinense community,the similarity between communities in adjacent restoration stage is higher than that in non-adjacent restoration stage.(2)Study on the model construction and its biomass allocation shows:Three models were used for regression analysis,above-ground biomass and trunk biomass is the best estimate effect,comparing with a lower estimate effect in leaf biomass and branch biomass.In order to maintain the consistency of the model for different restoration stages.We choose the model?to establish the optimum model for above-ground biomass of shrub to tree stage,model?is W=a+b(D~2H).And we choose the model?t o establish the optimum model for above-ground biomass of shrub stage and tree stage,model?is W=a×D~b×H~c.Based the established optimum model,we estimated biomass above-ground on the vegetation of L.chinense communities.The leaf biomass and branch biomass among different restoration stages order of size is shrub to tree stage,tree stage and shrub stage.The above-ground biomass and trunk biomass among different restoration stages order of size is tree stage,shrub to tree stage and shrub stage.The above-ground biomass of L.chinense contributed to the above-biomass of different restoration stages showed a decreasing trend across the succession.This illustrates the status of edificator of L.chinense in different restoration stages of L.chinense community may be replaced step by step,and backseat to the sub-tree layer.(3)Study on the community structure dynamic changes shows:The chemical potential values for different plant species ranged between-10.08 to 7.21,respectively,at the different restoration stages.The chemical potential value reflects the ability of different plant species to adapt the environment in karst area of Lijiang River Valley.Only one specie has a good applicability in shrub stage,respectively,there has 32 species and 25 plants have a good applicability in shrub to tree stage and tree stage,of which there has 19 common species in shrub to tree stage and tree stage.L.chinense played an important role as before in the persistence of stability of L.chinense communities.With succession proceeding,the number of growth potential of constructive species would increase in the future.Dominant species,like Croton xiaopadou and Albizia kalkora,would develop gradually,and take constructive species'place.Both eco-exergy and specific eco-exergy of the communities were kept increasing with fluctuations,which meant the community was developing towards a higher and higher stability and complexity.The development of structure in shrub layer experience bottlenecks due to the growth of species in tree layer,efficiently increased the canopy density and promoted the domination of shade-tolerant species in understory structure.(4)Study on the characteristic of soil ecohydro-function shows:With the restoration of L.chinense community,fierce competition among forest trees caused density tends to decrease,and basal area of shrub to tree stage is the largest in different restoration stage;Maximum moisture capacity of litter and soil permeability of shrub to tree stage is also the largest,shows that ground layer of shrub to trees stage has best function of water conservation and absorption capacity of surface runoff.Soil organic carbon and maximum moisture capacity gradually increased with restoration of L.chinense community,it shows soil nutrient mineralization capacity and moisture holding capacity become better and better as succession proceeds;And soil bulk density gradually decreased with restoration of L.chinense community,it shows the soil is becoming more porous and the aeration and water perviousness is becoming better.It is evident that soil ecohydro-function of tree stage is the best,the next is shrub to trees stage,and soil ecohydro-function of shrub stage is the worse.(5)From the species diversity,community structure and ecological function of way,and selection Simpson diversity index,pielou index,soil ecohydro-function index and eco-exergy value build community restoration degree.Apply grey correlation degree to assign weight of single component,and comprehensive evaluation the recovery mode of different restoration stages of L.chinense community.The results show that L.chinense community through natural succession got a different degree of recovery.Recover degree of shrub stage reached 45.3%,recover degree of shrub to tree stage and tree stage,respectively reached 87.4%and 91.3%,it shows recovery status of shrub to tree stage and tree stage obviously better than shrub stage.But based on the Simpson diversity index,pielou index,soil ecohydro-function index and eco-exergy value,which constitutes the recovery degree,the degree of recovery is not consistent.The process of L.chinense community transition from shrub stage to shrub to tree stage and development to tree stage,the recovery degree gradually increasing and the degradation degree gradually decreasing.This is consistent with the general law of restoration of degraded community.The change in recovery degree of shrub to tree stage and tree stage is not obvious,it shows that L.chinense community still takes a long time for succession to resume if it want to reproduce it best.