Abstract: An analysis was made on the diameter structure of the secondary forest of Adiessibirica Ledeb in the Northeast forest area.The Weibull distribution,Gamma distribution and Log-normal distribution were used for fitting stand diameter distribution and combined with χ² fitting result for examination.The results indicated that the average DBH of Adiessibirica Ledeb forest was 15.1cm,the least diameter class was 5.1cm,the maximum diameter class was 47.1cm,and,the accumulating percentage of diameter class(6-28)was 75.8%.Among the whole distribution functions,the R² Weibull was 0.997,the χ² was 6.35 and the distribution fitting effect is best,followed by the Gamma distribution,the Log-normal distribution was worst,but the difference between the frontal two distributions was similar,all of them can be used to predict Adiessibirica Ledeb diameter structure,which provided theoretical basis for diameter structure and stand density redjustment.

Key words: diameter structure, Abies nephrolepis, Weibull distribution, Gamma distribution, Log-normal distribution