绵阳官溪河流域防护林林木分化及异常木分布格局

对绵阳官溪河流域常见的几种防护林类型林木分化及异常木分布格局进行了研究。结果表明，防护林林木分化的结果以小径木占优势，尤以直径1cm～6cm的个体最多，占林分总个体数的60％以上。桤柏混交林、柏木纯林、松栎混交林、松柏混交林和松柏栎混交林的林木株数按径阶的分布表现出左偏态分布，直径大小的变异性较低；与之相比。栎黄荆次生灌丛和马尾松林不呈偏正态分布，直径大小的变异性较高。异常木直径主要分布在1cm～10cm范围内，其中倾斜木和倒伏木超过了异常木总数的50％，枯立木和濒死木中，马尾松林和松柏栎混交林较其它防护林类型少。异常木的分布格局除松柏栎混交林呈随机分布外，其余的皆呈聚集分布，但聚集强度不大。异常木聚集强度的大小与取样面积大小的关系表现为：Kuno．E．聚集度指标值（G）随取样面积的增大，由小变大，而Lloyd．M．平均拥挤度值（m^＊）则由大变小。

Natural Differentiation of Trees and Distribution Patterns of Abnormal-growth Trees in Protection Forests in the Guanxi River Valley, Mianyang

The study showed that dominant small-diameter trees in common protection forests of the Guanxi River Valley resulted from the natural differentiation of trees,and especially trees with a diameter of 1 cm to 6 cm were the most,accounting for over 60% of the total individual number in the stand.The diameter-class distribution of trees in mixed Alnus cremastogyne-Cupressus funebris forest,pure Cupressus funebris forest,mixed Pinus massoniana-Quercus forest,mixed Pinus massoniana-Cupressus funebris forest and mixed P.massoniana-C.funebris-Quercus forest exhibited a left bias truncated normal distribution curve,and the variability of their DBH size was lower,while that of trees in secondary Quercus-Vitex negundo scrub and Pinus massoniana forest did not display the above distribution curve,and the variability of their DBH size was higher.The diameter distribution of abnormal-growth trees ranged mainly from 1 cm to 10 cm,and in the protection forests there were more inclined trees and fallen trees,which were in excess of over 50% of abnormal-growth trees.Compared with other forests,there were more less snags and dying trees in Pinus massoniana forest and mixed P.massoniana-C.funebris-Quercus forest.The abnormal-growth trees of mixed P.massoniana-C.funebris-Quercus forest showed a random distribution,but that of other forest types displayed a clump distribution.As for clump distribution types,their aggregated degree values were not great,but were related to a sampling area size.Their relationship is as follows:Kuno.E.value (C_A) shifts from low to high while Lloyd.M.value (m~*) shifts from high to low with the increasing of the sampling area.