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一前言在营林工作中,评定立地质量是相当重要的。以往是根据林分平均年龄和林分平均高确定地位级,按地位级的高低来衡量立地质量的好坏。但同一林分扶育间伐前后的地位级是基本相同的,然一经间伐,林分平均高提高了,而林分年龄却不变,则其地位级有可能比间伐前提高1级,这是用地位级评定立地生产力的主要缺点。立地指数表是根据林分优势木平均高与林分平均年龄的关系编制的,且以标准年龄(基准年龄)为基础,按林分优势木的平均高度的变化幅度,划分为若干等级,并以该年龄优势高的绝对值作为指数。例如以20年为基准的立地指数18,意思是优势木在20年生时树高长到18米,有数量的概念,而不是一般质量的描述。因此立地指数是一种比较先进的评定有林地生产力的技术方法。指数越高,林地生产力越高。
Foreword In the forest management work, assessing the site quality is very important. In the past, the status level was determined according to the mean stand height of the stands and the mean stand height of the stands, and the quality of the site was measured by the rank level. However, the status of the same stands before and after the thinning was basically the same. However, after the thinning, the average height of the stands increased while the stand age remained the same, The main shortcomings of the status-level assessment of on-site productivity. The site index table is prepared based on the relationship between the average height of stand dominant trees and the average age of stands, and is divided into several grades based on the standard age (base age) and according to the variation range of the average height of stand dominant trees Take the absolute value of this age advantage as an index. For example, a site index of 18 on the basis of 20 years means that the dominant tree grows to a height of 18 meters at 20 years of age, with a quantitative concept rather than a general quality description. The site index is therefore a more advanced method of assessing the productivity of woodlands. The higher the index, the higher the productivity of woodland.