A Study on D iametra l Structure of Yunnan Pine Forestin the Pla teaus ofM id-Yunnan Province

Yunnan Pine is the p redominant woody tree in southwestern China as well as one of important forest resource in China. The paper give a study to Yunnan p ine forest in mid2Yunnan p rovince and Weibull distributionwereβ distribution were used to fit and forecast the diametral distribution regularity of natural and man-made Yunnan p ine forest. All distributionswere checked by xcheckingmethod. The results showed thatWeibull andβ distribution could describe the diametral distribution well. The curves’measure of skewness is left, and kurtosis value ispositive. The curves have the features of high p recision and good adap tability. Between them, Weibull distribution’s fitting is better thanβ distribution and could be used to forecast the yield, woody quantity and to evaluate management.