Species And Lineage Diversity Distribution Patterns Of Karst Plant Communities Based On Habitat Heterogeneity

Karst forest is an important treasure house of natural resources in our country,which contains abundant plant resources.Due to the exposed bedrock and abundant rainfall dissolution,many local microenvironments or niches are formed on the karst surface.The karst vegetation is formed by the combination of stone ditches,caves,rock joints,rock troughs and other niche types.The high heterogeneity of this kind of niche dominated by geological background is the key factor that constitutes the rich and diverse species of plant communities in karst areas.In the past,the related research on karst heterogeneity only stayed at the qualitative level,and the quantitative description of the degree of karst habitat heterogeneity is an urgent problem to be solved.This paper takes the niche as the starting point,constructs a comprehensive habitat heterogeneity index based on Shannon's information entropy theory,and quantitatively analyzes the degree of karst habitat heterogeneity.Through the survey of 53 wild plant community sample plots,the response characteristics of community diversity to niche component ratio and habitat heterogeneity were analyzed from the two dimensions of species and pedigree,in order to provide theories for revealing the formation and maintenance mechanism of biodiversity in karst areas It provides a reference and basis for resource protection and vegetation restoration in the area.The main results are as follows:(1)The species richness index,Simpson diversity index,and Pielou evenness index of the study area are generally in the order of shrub layer plants>herb layer plants>arbor layer plants.The Shannon-Wiener index appears as herb layer plants>shrub layer plants>arbor layer plants.The PD index of pedigree diversity is shown as shrub layer plants>herb layer plants>arbor layer plants;from the perspective of phylogenetic structure,the phylogenetic structure of the arbor layer and shrub layer shows an aggregated structure,and the phylogenetic structure of the herb layer shows a divergent structure.(2)Among all kinds of karst niches,soil surface and stone surface are absolutely dominant,and the niches of stone cracks,stone ditches,stone caves and stone troughs decrease in order.In terms of species richness and pedigree diversity,the species richness index of arbor layer,shrub layer,and community plants increases with the increase in the ratio of the niche components of stone ditch,stone crevice,stone cave,stone trough,and soil surface.All showed a single-peak change trend.The resource segmentation of stone faces and soil surfaces by stone grooves,stone cracks,and stone grooves increased species diversity and pedigree diversity,and further segmentation reduced species diversity and pedigree diversity.(3)In terms of species Alpha diversity,the species richness of arbor layer,shrub layer,community plant and the Shannon-Wiener diversity index along the habitat all show a clear intermediate height expansion pattern,both of which are in the moderate habitat.The qualitative(1.2-1.4)has a maximum value;the Simpson index and Pielou index of herbaceous plants increase sharply with the increase of habitat heterogeneity and then tend to be gentle and stable.As far as the species Beta diversity is concerned,the Cody dissimilarity index of the arbor layer and shrub layer showed a unimodal change as the habitat heterogeneity increased,and peaked in the moderate habitat heterogeneity;the herbaceous layer Sorensen and Jaccard similarity The index increases with the increase of habitat heterogeneity,from the moderate dissimilar of the lower habitat heterogeneity to the moderate similarity with the increase of the habitat heterogeneity.(4)In terms of pedigree Alpha diversity,the pedigree Alpha diversity PD index of tree layer,shrub layer,and community plants all showed a unimodal trend along the increase of habitat heterogeneity,and maintained the highest in moderate habitat heterogeneity.Genealogical diversity.The phylogenetic structure of the arbor layer exhibits an aggregated structure in the lower and middle habitat heterogeneity,and a divergent structure in the higher habitat heterogeneity.As far as the pedigree Beta diversity is concerned,the Beta diversity of the herb layer pedigree shows a sharp decrease trend in the lower habitat heterogeneity range,while the arbor layer plant shows a sharp increase trend in the higher habitat heterogeneity range.All in all,karst areas are rich in niche types,and the segmentation of niche resources affects the heterogeneity of habitats and further affects species diversity.The resource segmentation of stone surface and soil surface by stone trenches,stone cracks,and stone grooves increases species diversity,and further reduces species diversity.From the perspective of the habitat heterogeneity index constructed based on the combination status of each niche,lower or higher heterogeneity is not conducive to maintaining species diversity and pedigree diversity,while moderate heterogeneity maintains more species diversity and Genealogical diversity.The maintenance of karst species diversity on the mesoscale is a trade-off between niche resource segmentation ratio and heterogeneity.