Species Diversity And Interspecific Association Of Pinus Tabuliformis Mixed Forest In Huanglong Mountain

Species diversity is a key part of biodiversity, is the basis of describing the ecosystem process of community and the spatial distribution structure of species with its spatial pattern being important reference of community composition. Interspecific association is a key indicator of association between plants, distribution pattern and trends of population. A 1 hm2 plot of Pinus tabuliformis mixed forest on Huanglong Mountain was utilized and been divided into different scales. Characteristics and scale effects of species diversity and interspecific association, as well as the relationship between them was analyzed. Results showed that:(1) As the scale increased, the Richness had no clear trend, whereas Simpson, Shannon-Weiner and Pielou Diversity Indexes all stabilized after a certain scale, with their spatial variation de-creased. At scales of 5 000 m2 and larger, diversity index relationships between varying layers remained unchanged with the shrub layer having the greatest species diversity. The herb layer had the lowest species richness with higher uniformity for species distribution than tree layers.(2) Community overall associativity rendered as a non-obviousness negative connection at 100 m2 and 200 m2 scales, while it rendered as a non-obviousness positive connection at 400 m2 and larger scles. Synthesize the results of X2 test, percentage of co-occurrence and association coefficient, it was showed that Interspecific association has racial differences on different scales, the results of percentage of co-occurrence showed that interspecific connection strength weakened along with the increase of scale, while the results of X2 test and association coefficient showed that interspecific connection strength weakened and the number of species pairs gradually the majority along with the increase of scale. The research by Lin Yongming (2005) showed that the sampling size in which the ratio of positive connection and negative connection species pairs the closer to 1, was more suitable for interspecific association research. So,100 m2 is the most suitable sampling size for interspecific association research in the study area of this paper.(3) Synthesize the results of interspecific association at different scales, it is mainly positive connection between main tree species, mainly non-obviousness positive connection between main tree species and associated tree species, mainly negative connection between main tree species and occasional species. Indicated that there was great difference between main tree species and occasional tree species in habits and resource utilization. This means the main tree species have stress on the distribution of the occasional tree species. The occasional species will decline during succession. To protect the species diversity, the main species quantity should be controlled by thinning in the area that the occasional species distributed to give it enough space for living and weak the stress from the main species.(4) Species diversity and interspecific association are both key indicators for structure characteristics and spatial distribution of community, and both have scale effect. Therefore, in order to get better effects of forest management, the scale effect in addition to structure characteristics and spatial distribution of community should be considered when making forest management plans.