The Quantity Dynamics And Competitive Relationship Of Main Dominant Populations Of Evergreen Deciduous Broad-Leaved Mixed Forest In Karst Hills Of Guilin,Southwest China

Guilin is located in the northeast of Guangxi Zhuang Autonomous Region.It is the most typical and concentrated area of karst landforms in the world.It has the characteristics of high landscape heterogeneity,strong karst development,high rock exposure rate,strong carbonate dissolution and poor soil.As the main body of the karst hills ecosystem in Guilin,the evergreen deciduous broad-leaved mixed forest has an irreplaceable role and status in the restoration and protection of the karst forest ecosystem.Many ecological functions such as regulation,supply of forest products and maintenance of ecological balance play an important role.In order to explore the quantitative dynamics and competition relationship of the main dominant populations of the evergreen deciduous broad-leaved mixed forest in the karst hills of Guilin,we set up 2 hm~2sample plot in Long Village,Luojin Town,Yongfu County,Guilin City.Population as the research object,adopted DBH size grading method and leveling technique,compiled a static life table,drawn survival curve,mortality curve,disappearance rate curve and survival function curve,focusing on the research on the survival analysis of the main dominant populations.Population dynamics quantification method and time series prediction model were used to further analyze the change dynamics of the individual numbers of the main dominant populations of the evergreen deciduous broad-leaved mixed forest in the karst hills of Guilin and the development trend in the age classes of 2,4,6 and 8 in the future.At the same time,used Hegyi single tree competition index model analyzed the intraspecific and interspecific competition intensities of the main dominant populations in the evergreen deciduous broad-leaved mixed forest in the karst hills of Guilin.The results showed that:（1）The Cyclobalanopsis glauca population and Boniodendron minus population tended to Deevey-II type,namely stable type;Alchornea trewioides population and Callicarpa bodinieri population tended to Deevey-III type,namely growth type.（2）The changing trends of the mortality and disappearance rate curves are basically the same.However,compared with the Cyclobalanopsis glauca population and the Boniodendron minus population,the mortality and disappearance rate curves of the Alchornea trewioides population and the Callicarpa bodinieri population fluctuated more.（3）The Cyclobalanopsis glauca population and the Boniodendron minus population have the characteristics of"reduced equivalence in the early and middle stages,great competition pressure,and decline in the later stage";The Alchornea trewioides population and the Callicarpa bodinieri population have the characteristics of"sudden decline in the early stage,decline in the middle and later stages".（4）The quantitative change dynamic indices V_piand V’_piof the Cyclobalanopsis glauca population,Boniodendron minus population,Alchornea trewioides population and Callicarpa bodinieri population were all greater than 0,showing a transition from growth to stability.Among them,Alchornea trewioides population has the most obvious growth but not obvious stable trend,and is most sensitive to environmental changes.The growth of the Cyclobalanopsis glauca population is not obvious,but the stability trend is obvious,and the sensitivity to environmental changes is the least.（5）After 2,4,6 and 8 age classes in the future,the individuals of Cyclobalanopsis glauca population and Boniodendron minus population gradually concentrated to the aged individuals,while the growth rate of Alchornea trewioides population and Callicarpa bodinieri population increased with the increase of age class time.（6）Except that the intensity of intraspecific competition in Cyclobalanopsis glauca population is greater than that of interspecific competition,the Boniodendron minus population,the Alchornea trewioides population and the Callicarpa bodinieri population all showed that the competition intensity between species was significantly greater than that within species.（7）The target tree’s DBH/basal diameter of the Cyclobalanopsis glauca population,the Boniodendron minus population,the Alchornea trewioides population and the Callicarpa bodinieri population approximately obey the power function relationship with the competition index,intraspecific and interspecific competition index.