在加利福尼亚次生西黄松(Ponderosa pine)用材林遭受西部松大小蠹(Dendroctonusbrevicomis)和中欧山松大小蠹(D.ponderosae)的为害造成大量的经济损失.在1977年夏至1978年春连续两年干旱、虫害和病害的联合影响下小蠹致死树的地区已明显扩大.加利福尼亚大学Blodgett林业研究站正针对公有林和私有林研究害虫管理问题.该站设置在El Dovado县的西侧,内华达山中部的针栎混交林内.1955年以来研究站对危害松树的小蠹虫和根部真菌病(Verticicladiella wagnerii)作了一些工作.虽然对这些病虫害进行了广泛的昆虫学和病理学的研究,但直至1977年夏季在小蠹虫发生地周围40公顷采用疏伐研究以前,从未试图用营林措施来管理松林.本研究使用“聚类”方法,大体依据砍伐前西黄松受小蠹为害后危险轻重程度分组.这种方法承认混交针叶林包含不同组成成份,如树种组成、林分结构(树高、断面积)、立木年龄.树种组成在以往一段时间内是变化着的,因此需要通过识别和分析,以正确测定这种变化.本文研究西黄松林分类型特征,测定何种林分类型,承受小蠹和真菌病为害其损失最低.同时研究小蠹和根部真菌病对松林单株资料和小区资料死亡率.在内华达山西部混交外栎林,林木单株危险等级系统与害虫侵袭和致死率无关,随机或有意在具独立树 A substantial economic loss caused by the dendroctonus pubicomis and D. ponderosae in the secondary timberlands of Ponderosa pine in California was a drought for two consecutive years in the summer of 1977 and the spring of 1978, The area under the combined effects of pests and diseases has led to a significant increase in the lethal tree population. The Blodgett Forestry Research Station at the University of California is investigating pest management in public and private forests on the western side of El Dovado County, in the central Sierra Nevada Pinus arborescens mixed forest .Some work has been done on the beetles and the root mycosis (Verticiclaliella wagnerii), which have been detrimental to the pine trees since 1955. Although a wide range of entomological and pathological studies have been conducted on these pests, until the summer of 1977 Pine forest has never been managed by silviculture before 40-hectares of bark beetle were used for the study of deforestation.In this study, “clustering” method was used to classify the pine forest according to the degree of danger and severity This method recognizes mixed coniferous forests that contain different components, such as species composition, stand structure (tree height, cross section ), Stand age.Tree composition has changed in the past period of time, and therefore need to be identified and analyzed to correctly measure this change.This paper studied the characteristics of Pinus tabulaeformis forest type, to determine what type of forest, And mycosis.The results showed that there was no significant difference in the single wormwood and root fungal disease on single plantation data and community data mortality in the mixed forest of mixed oak and mixed forest in west Sierra Nevada, Random or intentional with independent tree