林龄和立地对渭北黄土高原刺槐和油松人工林的影响

基于双因子等级模型对龄级和立地好坏两个因子对渭北黄土高原刺槐和油松人工林的主要林分参数的作用效应进行了方差分析.结果表明龄级对大部分林分参数的影响不明显,虽然龄级内林分的上层高、密度、断面积等的实际年龄加权均值趋于随着龄级的增长而增加.很多龄级内"好”和"差"立地之间,林分参数除上层高外,差异也不显著.这是因为龄级内的林分利用方法和强度差别较大导致龄级内林分参数变差大于龄级间所致.一般是立地越好利用强度越大,因而导致好的立地上林分每公顷断面积和蓄积量低于差的立地上的林分.

Effects of Age and Site Goodness on the Growth of Black Locust (Robinia pseudoacacia L. ) and Chinese Pine (Pinus tabulae formis Carr. ) Plantations on the Weibei Loess Plateau

Based on the two factor hierarchic model, the effect of age class and site goodness on the major stand parameters of the black locust and Chinese pine plantations on the Weibei Loess Plateau were analyzed. It is concluded that the both factors have no any significant effects on most of the stand parameters, all through their weighted means by age tend to increase with the age classes. Between "good" and "bad" sites, the differences of most of the parameters aren't significant either. The reason for that is the desperate intensities and methods of intermediate cutting which caused a rather bigger variation of stand parameters within age classes than that between age classes. Generally, the better the sites are, the more intensive they are utilized. Therefore basal area and stocking volume of the stands on better sites are often smaller than that on worse sites.