杉木幼龄林直径分布

Stand Diameter Distribution Model of Young Chinese Fir Plantations

林分直径分布影响树木的树高、干形、材积及树冠等因子的变化，也是森林经营技术及测树制表技术的理论依据。本文基于6种理论生长方程和4种Fuzzy分布函数，对杉木幼龄林林分直径分布进行模拟，并且针对方程拐点的取值，讨论模拟精度高低产生的原因。结果表明：Richards方程、Weibull方程及Fuzzy－4分布对杉木幼龄林直径分布的拟合效果突出；杉木幼龄人工林林分直径累积分布曲线的拐点主要分布区间为0．50～0．65；方程拐点的取值情形与方程模拟精度的大小密切相关，具有拐点的方程模拟精度明显高于无拐点的方程，具有浮动拐点的方程的精度高于具有固定拐点的方程，korf例外；曲线的有效拐点区间愈大，拐点愈接近实际的林分拐点分布，则拐点的有效性越大，从而方程模拟精度越高。

We used six growth equations and four fuzzy distribution functions to simulate diameter distribution model of young Chinese Fir Plantations, and discussed the causes of simulation precision of equations based on the inflection point.Rich-ards distribution model, Weibull distribution model and Fuzzy-4 distribution function better expressed the diameter distri-bution and the fitting effect.The inflection points of curve of stands cumulative diameter distribution mainly ranged in 0.50-0.65.There was a close correlation between the value of inflection points of the equations and the modelling precision of equa-tions.The simulation precision of equations which with inflection point was obviously higher than that of without inflection point equations, equations with floating point precision was higher than the equation with fixed point except korf.The wider the effec-tive inflection point range of curve was, the closer the distance of the inflection point and the actual distribution of stand point was, the bigger the validity of inflection points was, and the higher the modelling precision of equations would be.