Biomass And Distribution Of Woody Plants And Their Response To Environmental Factors In Karst Communities In Central Guizhou

The environment in karst area is complex,and plant biomass has a strong response to the changes of environmental factors.In order to explore the relationship between plant biomass and environmental factors in karst area and the allocation strategy of biomass of main species and organs.Taking the karst secondary forest in Tianlong mountain of Puding County in Central Guizhou as the research object,the top 8 dominant species ranked by important value(IV)were selected: Lithocarpus confinis,Platycarya strobilacea,Itea yunnanensis,Machilus cavaleriei Levl,Pittosporum brevicalyx,Carpinus pubescens,Lindera communis Zanthoxylum dimorphophyllum calculated the aboveground biomass of the community through the biomass regression model,and analyzed the relationship between the aboveground biomass of the community,life form,species and environmental factors by using spatial distribution map,correlation test(person),general linear model(GLM)and redundancy analysis(RDA),;The relative growth relationship of organ biomass of dominant species was analyzed by descending principal axis regression(RMA),and the relationship between plant components and environmental factors was analyzed by general linear model and correlation test.The research results are as follows:(1)The total community biomass in 2020 was 106.94t/ha,an increase of 29.36t/ha compared with 2012,and the growth rate began to slow down after 2015.In the three surveys,the aboveground biomass of evergreen plants is higher than that of deciduous plants,and the biomass of dominant species always occupies a dominant position in the community.Lithocarpus confinis and Platycarya strobilacea are the main producers of the aboveground biomass of the community.They account for about 34%of the aboveground biomass of the group from 2012 to 2020.Although Pittosporum brevicalyx has high community dominance,its biomass accounts for very little.The number of class I plants decreased gradually,but the initial biomass increased steadily.The number of class I plants was significantly more than that of class II plants.The aboveground biomass of class II plants was the main provider of aboveground biomass of the community.(2)The distribution of community biomass is discontinuous,and the spatial distribution of evergreen plants and deciduous plants is significantly different.Evergreen plants are mostly distributed in the middle and lower slopes of the sample plot(y < 80),while deciduous plants are concentrated and distributed in the upper slopes of the sample plot(Y > 40).The distribution states of different species are quite different.The distribution Lithocarpus confinis and Platycarya strobilacea tends to be consistent with the difference between evergreen and deciduous plants,The biomass of other species showed discontinuous distribution in space,except that Carpinus pubescens showed obvious agglomeration distribution in space(x< 60,y < 50).The spatial distribution of rock exposure rate shows obvious gradient difference between the upper slope(Y > 70)and the lower slope,while the spatial distribution of slope and soil thickness is broken,and the distribution of community biomass tends to be consistent with soil thickness.(3)There was a significant positive correlation between soil thickness and community biomass(P < 0.05),and there were different correlations between environmental factors.Soil thickness was the main influencing factor of community biomass(0.505).For different life forms,the impact of rock exposure rate on plant biomass was the highest(0.386,0.412),while the impact of soil thickness and slope on evergreen plant biomass(0.268)was greater than that of defoliation(0.094),For different species,the correlation between biomass and environmental factors is more complex.Soil thickness is positively correlated with most dominant species.Rock exposure rate and slope are positively correlated with Huaxiang tree and prickly ash respectively.(4)The biomass of branches and stems accounted for most of the aboveground biomass of plants,among which the biomass of Platycarya strobilacea was the highest,accounting for 15.34%.The relationship between leaf biomass and branch biomass of the four species showed allometric growth.The growth rate of branches was higher than that of leaves.There was significant difference in growth rate among species,and the related growth index of Platycarya strobilacea ?(1.02)the lowest,the input of chemical fragrant tree to leaf growth is greater than that of the other three species,and Machilus cavaleriei Levl is the highest(1.35).There was an isokinetic growth relationship among leaf biomass,branch biomass and aboveground biomass,and there were some differences in relevant growth indexes among species.(5)The correlation between different plant components and environmental factors converged,and there were only differences in specific correlation coefficients.The slope had a significant negative correlation with Itea yunnanensis(P < 0.01),the rock exposure rate had no correlation with Itea yunnanensis only,and the soil thickness had a significant positive correlation with the component biomass of Lithocarpus confinis and Machilus cavaleriei Levl(P < 0.01).The three environmental factors had certain effects on the biomass of different plant components,and the rock exposure rate had the highest effect on Lithocarpus confinis and Platycarya strobilacea.Generally speaking,soil thickness is the main factor affecting the aboveground biomass of karst secondary forest group.For different life forms and species,due to the influence of biological factors such as plant characteristics and interspecific relationship,the influence mode of environmental factors on plant biomass is more diversified.Habitat differentiation dominated by rock exposure rate is one of the important mechanisms for the coexistence of different life forms of plants in Karst secondary forest in Tianlong mountain.