Population Structure And Dynamics Of Betula Luminifera In Evergreen Deciduous Broad-leaved Mixed Forest In Different Regions Of Southwest Hubei

Betula luminifera is one of the main pioneer tree species in subtropical evergreen deciduous broad-leaved mixed forests in china.exploring the structural characteristics and dynamic variation law of Betula luminifera population in different communities is helpful to deeply understand the role of community construction mechanism in the maintenance mechanism of species diversity in different regions.The Betula luminifera of forest dynamic plot of 27 hm² of subtropical evergreen deciduous broad-leaved mixed forest in Mulinzi National Nature Reserve?Qizimei Mountian National Nature Reserve and Lichuan Jinzi Mountain State-owned Forest Farm three regions of southwest Hubei province was studied in this pape.Using the method of space for time,the static life table was compiled,the survival curves mortality rate and disappearance rate curves were drawn,and the structural characteristics of Betula luminifera population in different regions were analyzed.The spatial distribution characteristics Betula luminifera populations were analyzed by pair-correlation function,and the space correlation between different life-history stages were explored by bivariate pair-correlation function.Four survival analysis functions were used to analyze the dynamic change trend of Betula luminifera population in different regions.The main research are as follows:?1?There are great differences in the population structure of Betula luminifera in the area of Mulinzi,Qizimei Mountain and Jinzi Mountain.The population of Betula luminifera in Mulinzi is mainly maintained by middle-aged individuals and tends to decline;The transition from stable to declining population structure of Betula luminifera in Qizimei Mountain;The population of Betula luminifera in Jinzi Mountain is abundant among young individuals and stable.?2?Static life table analysis results,the population of Betula luminifera in three regions gradually decreased the survival number and the life expectancy decreased with the increase of age class.The number of surviving individuals of the Mulinzi and Qizimei Mountain populations showed some volatility.According to the survival curves and equations to test that the population of Betula luminifera approached to model Deevey-?.The mortality rate and disappearance rate curves showed that the Betula luminifera population fluctuated in different degrees in each regions,especially in the Qizimei Mountain population.?3?Dynamic change index of population structure of Betula luminifera in each region(V_pi>0).The dynamic index of the number individuals in the adjacent age class of the Betula luminifera population in the Mulinzi and Qizimei Mountain showed a decline trend?V_n<0?.Maximum risk of random disturbance P=0.05 for Betula luminifera population in Mulinzi,minimum sensitivity to external disturbance.Maximum risk of random disturbance P=0.09 for Betula luminifera populations in the Qizimei Mountain and Jinzi Mountain,which is more sensitive to external interference.?4?The spatial distribution and population density of the Betula luminifera populations in different regions and their growth stages are quite different.The spatial distribution characteristics of Betula luminifera population and growth stage in each region are the gradual transition of the aggregation distribution to the random distribution,and the spatial aggregation degree and scale gradually decrease with the increase of the age class.The aggregation degree of Mulinzi and Qizimei Mountain populations was the highest in young tree.the aggregation scale small tree stage is the largest.The aggregation degree and aggregation scale of the population in the Jinzi Mountain are the highest in the young tree.?5?The intraspecific spatial correlations of the species in the growth stages of the Betula luminifera populations in the Mulinzi,Qizimei Mountain and Jinzi Mountain,under the complete spatial randomness model,the overall performance is spatially positive correlation,and the mutual exclusion is not obvious.Under the antecedent condition model,the Mulinzi and Jinzi Mountain Betula luminifera populations are spatially independent,and the Qizimei Mountain populations are spatially correlated in a partial scale.?6?The results of survival function analysis show that the population of Betula luminifera in each regions has the characteristics of intense competition in the early stage and dynamic stability in the middle and late stage,and the environmental pressure and population competition had different effects on the population of Betula luminifera.The trend of population mortality density and hazard rate curve change is basically the same,among them,the Qizimei Mountain population appears“double peak”in the II and IV age class.The population survival rate and cumulative mortality rate curves showed that the Mulinzi and Qizimei Mountain populations entered the successional decline earlier than the Jinzi Mountain population.