【摘要】 对于直径遵从正态分布的同龄纯林 ,通常只从经验上判定其平方平均直径在株数累积分布曲线上的位置介于 5 5 %～ 6 4%之间 .该文从林分算术平均直径 ( d) ,林分平方平均直径 (Dg)和直径变动系数 (c)三者之间的数学关系 ,导出f(c) =1+c2 - 1 c是正态分布的分布函数的自变量 ,并从数学上证明了其Dg 的株数累积百分数的范围在 5 4%～ 5 6 8%之间 ,同时介绍了用Excel中Normsdist函数求解Dg 株数累积百分数的方法 ,并用一组数据进行验证 ,计算结果与实际情况吻合 ,可靠性 95 %以上 .更多还原

【Abstract】 The square average diameter cumulative percent ( SADCP ) of even aged stand complied with normal distribution is experientially between 55% and 64% on diameter cumulative curve. This paper indicates that the formula \%f(c)=1+c\+2-1/c\% got from the relationship of stand arithmetical average diameter (\%\%), stand square average diameter ( D g) and diameter correlative coefficient ( c ) is the variable of normal function, and proves that the SADCP is between 54% and 56 8%. This paper also introduces another method using the function Normsdist of Excel to calculate SADCP . Finally a series of data is used to test this method, and the result is perfect and the reliability is more than 95%.更多还原