Study On Community Characteristics Of Woody Plants And Soil Physical And Chemical Properties At Difference Terrains Of Maolan

Maolan Nature Reserve is an ideal place to study the theory of karst forest ecosystem and geomorphic development.Compared with the forest ecosystem in the normal landform,karst forest has obvious differences in community nature,species composition,community appearance,habitat characteristics,spatial structure and succession dynamics,even in the internal animal composition,population dynamic development and the impact of ecosystem on the environment.Based on the division of the functional groups of woody plants in Maolan Karst forest by predecessors,taking the woody plants and soil in the community as the research object,the woody plants in three topographical parts（hillside,valley and funnel）in the study area were investigated,and the species composition,species diversity,life form,diameter class and height class structure of the woody plant community and the terrain difference of the distribution of the main dominant species were analyzed differently.The indoor analysis of soil physical and chemical properties of three topographical parts was carried out,and the distribution difference and seasonal change rule of soil physical and chemical properties of different topographical parts were analyzed.The relationship between plant diversity and soil physical and chemical properties of three topographical parts was analyzed by RDA sequencing.In order to provide theoretical basis for the study of the maintenance mechanism of species diversity in karst forest ecosystem in Maolan,and play an important role in ecological maintenance and biodiversity protection.The following conclusions are drawn:（1）According to the sample plot investigation,there were 78 species of woody plants in 65 genera,35 families in the hillside,89 species of woody plants in 64genera,38 families in the valley,84 species of woody plants in 61 genera,35 families in the funnel,there are 43 families of woody plants distributed in all three terrains,30families of woody plants were distributed in the hillside,the valley and the funnel,accounting for 69.8%of the total families,Lauraceae and Rosaceae were distributed in three topographical parts and all of them were dominant families.Among them,the hillside was dominated by small and low high-level bud plants;the valley was dominated by medium and high-level bud plants and small high-level bud plants;the funnel was dominated by medium and high-level bud plants and large high-level bud plants.（2）In the tree layer,Margalef richness index,Shannon Wiener diversity index and Pielou evenness index all showed Valley>funnel>hillside in the three topographical parts,while Simpson dominance index showed hillside>funnel>Valley in the three topographical parts.In the shrub layer,Margalef richness index,Shannon Wiener diversity index and Pielou evenness index all showed valley>hillside>funnel in the three terrains,while Simpson dominance index showed funnel>hillside>Valley in the three terrains.（3）In the diameter class distribution diagram,the proportion of tree species in the first diameter class was shown as hillside>funnel>valley,the proportion of tree species in the second,fourth and fifth diameter classes was shown as valley>funnel>hillside;the proportion of tree species in the third diameter class was shown as valley>hillside>funnel;in the height class distribution diagram,the proportion of tree species in the shrub layer was shown as funnel>hillside>valley.The proportion of tree species in the lower and middle layers of trees was valley>hillside>funnel;the proportion of tree species in the upper layer of trees was valley>funnel>hillside.（4）The important values of different layers（arbor and shrub layer）of woody plants in three different topographical parts were calculated.In the hillside,the main dominant species of arbor layer were Litsea verticillata,Viburnum henryiand,Cladrastisplatycarpa,and the main dominant species of shrub layer were Viburnum propinquum,Nandina domestica,Brassaiopsis glomerulata,etc;in the valley,the main dominant species of arbor layer were Litsea verticillata,Dendrobenthamia japonica,Machilus rehderi.,and the main dominant species of shrub layer were Euonymus dielsianus,Nandina domestica,Sinosideroxylon wightianum,etc.;In the funnel,the main dominant species in the tree layer were Cyclobalanopsis glauca,Machilus rehderi,Dendrobenthamia japonica,etc.in the shrub layer,the main dominant species in the shrub layer were Pittosporum crispulum,Sinosideroxylon wightianum and Nandina domestica,etc.（5）The physical and chemical properties of soil in the study area were relatively stable,and the coefficient of variation was small.Among the three topographical parts,the range of pH,bulk density,total capillary porosity,capillary porosity,non capillary porosity,inter field water holding capacity and natural water content was 6.85～7.57,0.93～1.12g·cm^-3,57.75～64.80%,37.15～52.01%,7.36～22.34%,34.60～54.57%and 31.19～50.19%,respectively.Organic matter,total nitrogen,alkali hydrolyzed nitrogen,total phosphorus,available phosphorus,total potassium and available potassium varied from 68.57～261.77g·kg^-1,3.85～10.15g·kg^-1,303.51～564.84mg·kg^-1,1.53～3.63g·kg^-1,3.17～12.03mg·kg^-1,4.65～10.88g·kg^-1,65.57～154.70mg·kg^-1,respectively.The pH value,bulk density and non capillary porosity were hillside>valley>funnel.Natural water content,field capacity,total porosity and capillary porosity,organic matter,total nitrogen,alkali hydrolyzed nitrogen,total phosphorus,available phosphorus,total potassium and available potassium were all funnel>valley>hillside,and most of the indexes of soil nutrients were higher in summer and autumn than in spring and winter.（6）The three species diversity indexes of Margalef richness index,Shannon Wiener diversity index and Pielou evenness index in the woody plant community in the study area were positively correlated with most of the soil physical and chemical indexes,while Simpson dominance index was negatively correlated with most of the soil physical and chemical indexes.Among them,alkali hydrolyzed nitrogen,available phosphorus and total potassium were important soil environmental factors,which had the greatest impact on plant community species diversity.The change trend of species diversity index of tree layer and shrub layer was different with soil physical and chemical properties.The relationship between species diversity index of tree layer and shrub layer was negative correlation.