Comparison of Diameter Structure of Four Forest Types in Jilin Province

Analysis was made on diameter structure of four forest types,including mixed coniferous and broad-leaved forest,mixed broad-leaved forest,Quercus mongolica plantation and Larix olgensis plantation,in Wangqing county of Jilin province.Diameter distribution of the above-mentioned forest types is fitted by four distribution functions of normal distribution,Weibull distribution,Gamma distribution and lognormal distribution,and meantime,Chi square statistics is used for test.The result showed that Gamma distribution function had better fitting effect for diameter distribution of mixed broad-leaved forest and Q.mongolica plantation,and Weibull distribution one for mixed coniferous and broad-leaved forest and L.olgensis plantation.