The nonparametric kernel density theory and methods are introduced to model the diameter distribution of broadleaved Pinus koraiensis in Liaoning eastern mountains in contrast with the normal distribution and Weibull distribution.

stand for water resource conservation,the growth process and diameter distribution characteristic of Larix Principis-rupprechtii Plantation in 10 years old were studied using stem analysis method of sample tree,which had two density structures(one was 2 600 per hm2,the other was 3 500 per hm2) in water conservation forest region of Wutai Mountain in Shanxi Province.

The method is as follows: use Laser Particle Sizer to obtain data of frequency distribution (calculous), cumulative distribution (integral) and then build mathematic model, lastly do research with computer and combined wit.

Based on the data collected from the 16 sampling plots and 256 sampling squadnats in Picea classifolia community at Qilian Mountains forest area in Gansu Province,this paper analyzed the frequency distribution,synusia structure,and dynamic of Picea ctassifolia community.

It is hypothesized that frequency distribution of both grammatical and lexical cohesion is much higher in good composition than that in poor ones.