Point Pattern Analysis And Similarity Study Of The Quercus Species At Baotianman,Henan,china

Point pattern analysis is a common method for ecological research at present.It is commonly used to detect the spatial pattern of species,to study the intraspecific correlations between different diameter classes of the same species and to study the interspecific correlations between different species.On the basis of these researches,we can make the further study on the action mechanisms of ecological process such as habitat heterogeneity,density dependent effects and dispersal limitation etc.,and then we can derive the mechanisms of species coexistence and the diversity maintenance.And combined with other subjects,we can explore the interaction between plants and animals or soil microbes and so on.The congeneric species have the same origin in the evolutionary history,so its physiological characteristics may have certain similarities.Our research used the point pattern analysis to study the spatial pattern of several dominant species at Baotianman National Nature Reserve in Henan Province.At the same time,in order to understand the role of the habitat heterogeneity and the density dependent effects in the maintenance of species diversity,and in order to explore the maintenance mechanism of the dominant species further,this paper uses the pair correlation function g(r)to studied the dominant Quercus aliena var.acutiserrata species in Baotianman National Nature Reserve.The results showed that:(1)The spatial distribution patterns of these Quercus species are similar;they all show aggregated distribution.The distribution trends of these Quercus species are consistent in the plots,and the interspecific correlations between these Quercus species are very weak.In addition,the interspecific correlations of each Quercus species in the plots are very similar,mainly show negative correlations.In addition,when combined with the individual number and the degree of aggregation of these Quercus species,we found that the intensity of overall negatively correlations which come from the Quercus species to the other species are related to the individual number and the degree of aggregation of these Quercus species.By studying the after-merged population of these congeneric species,we found that the interspecific correlations of after-merged population are similar with the interspecific correlations of each Quercus populations individually.The weak interspecific relationship between these congeneric species and the differences in the overall intensity of interspecific correlations between before-merged populations and after-merged populations of these congeneric species showed that the species which have the similar niches can coexist.These congeneric species may have an influence on and resist the impacts from the other species as a whole.The coexistence mechanism among these congeneric species is very helpful to protect the development of the congeneric species which have the fewer individuals in the community.(2)In the studying plot,the spatial distribution pattern of Quercus aliena var.acutiserrata showed obviously aggregation pattern,which indicates that the Quercus aliena var.acutiserrata is significantly affected by habitat heterogeneity,and also shows that the habitat in this plot is very suitable for the growth of Quercus aliena var.acutiserrata.After excluded habitat heterogeneity,by comparing the difference in spatial distribution patterns between the dead trees and the live trees of Quercus aliena var.acutiserrata,we found that the distribution of Quercus aliena var.acutiserrata is significantly affected by the density dependent effect.Further research on the intraspecific correlations and the interspecific correlations of Quercus aliena var.acutiserrata found that,the intraspecific correlations between the dead trees and the live trees of Quercus aliena var.acutiserrata and the intraspecific correlations between different diameter classes of Quercus aliena var.acutiserrata have all showed weak positive correlations.And the intraspecific correlations between Quercus aliena var.acutiserrata and other species are asymmetric,though the influences from the live trees of Quercus aliena var.acutiserrata to other species mainly show significant negative correlation,the impacts from other species on the live trees of Quercus aliena var.acutiserrata chiefly show significant positive correlation,which helps Quercus aliena var.acutiserrata to be the dominant species in the community.At the same time,although the influences from the dead trees of Quercus aliena var.acutiserrata to other species in the plots mainly show significant negative correlation,the impacts from other species on the dead trees of Quercus aliena var.acutiserrata also primarily show negative correlation,these indicate that the death of the dead trees is likely due to the interspecific competition,that is to say,the density dependent effects of Quercus aliena var.acutiserrata mainly come from the interspecific competition.In addition,the impacts from other species on the different diameter classes of Quercus aliena var.acutiserrata are different,other species show a strong negative correlation to the saplings of Quercus aliena var.acutiserrata,whereas the negative correlations to the bigger diameter classes of Quercus aliena var.acutiserrata are weaker,which is the cause of a large number of dead saplings of Quercus aliena var.acutiserrata.Above all,there are many similarities between congeneric species.They have similar spatial patterns in the same plot,and the spatial distributions of these congeneric species are also consistent with one another.The influences from the Quercus species to the other species are very similar,and there are weak correlations between congeneric species,only show weak positive or negative correlations on a very few scales.This indicates that the congeneric species can coexist in the same habitat,and it can merge together as one species to interact with other species.At the same time,this study found that habitat heterogeneity,density dependent effects and intraspecific or interspecific correlation can affect the spatial distribution pattern of the community.The suitable habitat,the mutual assistance in the intraspecific correlations of Quercus aliena var.acutiserrata,and the positive associations in interspecific correlation of Quercus aliena var.acutiserrata are the main reason for a dominant Quercus aliena var.acutiserrata species to maintain its dominance in the community.This study examined the role of the ecological mechanisms such as habitat heterogeneity and density dependent effects in community construction.Our results are useful for understanding the maintenance mechanism of species diversity,and provide ideas for the further study on coexistence mechanism among the congeneric species.