Point Patterns Analysis Of Forest Community In Permanent Plots At Baotianman National Nature Reserve

The spatial pattern of species reflects the basic characteristics of the population. The study on the spatial distribution patterns of species is important for understanding the relationship between population characteristics, species and environment interactions and relationships among species. Although many scholars have studied the spatial pattern of species, few have examined the variation of spatial distribution patterns and of species correlation in different growth stages. And even fewer people to explore the differences of species correlation among different diameter classes of different life forms. Based on point pattern analysis, we examined the spatial distribution pattern and interspecific correlation of 14 species which individual number are greater than 100 at Baotianman at two 1 ha plots. The 14 species belong to three life forms; they are shrub species, including Symplocos paniculata, Forsythia suspensa, Philadelphus incanus and Euonymus alatus; small arbor species, including Bothrocaryum controversum, Carpinus hupeana var. henryana, Carpinus turczaninowii, Tilia japonica, Lindera obtusiloba, Sorbus alnifolia and Dendrobenthamia japonica var. chinensis; arbor species, including Quercus serrata var. brevipetiolata, Quercus aliena var. acuteserrata and Quercus variabilis. The mainly results of this article are as follows:The spatial distribution patterns of the 14 species in these plots are aggregated under the complete spatial randomness model, and the aggregation of the species on the large scale is significantly reduced after the use of the heterogeneous poisson model to remove the environment heterogeneous. And the variation in spatial distribution patterns of adult trees between before and after the exclusion of environment heterogeneity is big, but the variation of sapling is relatively small. This indicates that the spatial distribution patterns of these species are significantly affected by environmental heterogeneity. And the spatial distribution patterns of species are more likely to affect by environmental heterogeneity on a larger scale. At the same time, as the adult tree has experienced a long time of natural selection and environmental impact, the distribution pattern of the adult tree reflects the influence of environmental heterogeneity. But the spatial distribution patterns of sapling may be more related to the dispersal limitation of seed and the intraspecific or interspecific correlation.The interspecific correlations in the plot are dominated by competition, but most species showed a negative correlation with other species only on a few scales. And shrub species are severely affected by the other species, small arbor species show a great impact on the other species, the arbor species have a great impact on the other species and are severely affected by the other species. In addition, the adult trees are positive correlation to the sapling in the same species, but the interspecific correlations show a significant difference among different life forms and among the different growth stages of species. Each growth stages of shrub species show great negative correlations to the saplings of arbor species; the adult trees of small arbor species show big influences on the saplings of shrub species; each different growth stages of arbor species have great negative correlations to the each growth stages of shrub species. The variation in interspecific correlation between diameter classes in the No.l plot is relatively small, and the competition in the community has a decreasing trend; however the variation in interspecific correlation between diameter classes in the No.2 plot is relatively big, and the competition in the community has a increasing trend. This indicates that the micro environment around adult tree is more suitable for the growth of the sapling of the same species. But the differences in the correlations among different diameter classes may be related to the ecological characteristics of different life forms. And the interspecific correlation of one diameter class is the result of the interaction between the diameter class and the other species during the growth process of the diameter classes. The variation of interspecific correlation between different diameter classes reflects the dynamic changes of community structure. And the relationship among the saplings, to some extent, may indicate the future correlation between species. In addition, the interspecific competition in No.1 plot reduced gradually, the community structure is relatively stable; but the interspecific competition in No.2 plot increased significantly, and the species diversity is higher than No.1 plot, the community in No.2 plot may at the succession stag. These all have a great application value for the protection of endangered rare plants, for the utilization of plant resources and for the development and maintenance of the forest in the future. And it is helpful to the further research on the succession of the community and on the coexistence mechanism of species.