Abstract:

Diameter distribution is one of the key factors to reflect the characteristic of forest stand. Based on the long-term investigation data on the Jingouling Forest Farm which belongs to the Wangqing Forestry Bureau in Jilin Province，negative-exponential function was used to model the diameter distribution in different years. The parameters a and K were calculated. Result shows that a and K were decreasing along time. Thus，a and K were supposed as functions of time. After the estimating of a and K，the diameter distribution model was established. Then we used this model to predict the diameter distribution，and compared with the observed diameter distribution. Result shows the model we draw in this study is well-behaved. The diameter distribution was usually used to present the instant structure of stand in previous study. This study shed light on the prediction model of diameter distribution，and also it is very important in forest modeling.

Key words: natural uneven-age forest, negative-exponential, regression, diameter distribution