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1 前言地位级是反映林木生长的立地条件好坏和林分生产力的指标。地位级的优劣是以一定年龄的林分平均树高的差异划分的,这种划分方法只适用于单纯的同龄林。在农田防护林规划设计和经营管理工作中,对于立地条件的调查和地位级的划分具有十分重要的意义。因此,只有对森林生长的立地质量有一定了解,才有可能采取相应的营林措施,改善立地条件,提高林分生产力,所以立地条件的调查和地位级的划分又是研究森林的生长和收获以及规划设计的基础。从50年代起,我国编制了许多不同地区、不同树种的地位级指数表。但是我国从1978年开展“三北”防护林一期工程以来,
1 Preface Geographical level is to reflect the growth of forest site conditions of good and bad forest stand productivity indicators. The advantages and disadvantages of status level is divided by the average tree height difference of a certain age, this method of division applies only to the simple same age forest. In the planning, design and management of farmland shelterbelts, it is of great significance for the investigation of site conditions and the division of status levels. Therefore, only by understanding the site quality of forest growth, it is possible to adopt appropriate silvicultural measures to improve the site conditions and improve the stand productivity, so the investigation of site conditions and the classification of status levels are also to study the growth and harvest of forests As well as planning and design basis. Since the 1950s, our country has compiled a number of status-level index tables for many different regions and different species of trees. However, since the first phase of the “Three North” shelterbelt started in 1978 in our country,