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宁夏贺兰山前的淡灰钙土地带是“三北”防护林的重要地段。这一地带的一些林场(如宁夏青铜峡县树新林场),在建场初营造耐旱的小叶杨纯林,单位面积木材蓄积量低,病虫害严重;后来营造杨树、刺槐混交林,结果单位面积木材蓄积量显著提高,病虫害大为降低,受到了当地有关部门的重视。混交林可改善林分生长状况,早已为国内外造林部门所证实,但其速生丰产的机理目前尚缺乏资料。为此,我们几年来(1975—1982年)对树新林场混交林和纯林的林分生长状况和立地条件进行了调查研究,探索混交林速生丰产的机理,为在淡灰钙土地带科学造林提供理论根据。
The light gray soil zone in front of Helan Mountain in Ningxia is an important part of the “Three Norths” shelterbelt. Some forest farms in this zone (such as Shuxin Forestry Farm of Qingtongxia County, Ningxia Province) built a drought-tolerant young Populus euphratica forest at the early stage of construction, with low volume of timber per unit area and serious diseases and insect pests. Later, poplar and black locust mixed forests were established. As a result, Significantly increased the stock of timber, pests and diseases greatly reduced by the local authorities concerned. Mixed forest can improve stand growth, which has long been confirmed by afforestation departments at home and abroad, but the mechanism of fast-growing and high yielding is still lack of information. Therefore, in recent years (1975-1982), we studied the stand growth conditions and site conditions of mixed forest and pure forest in Shuxin Forest Farm, explored the mechanism of fast-growing and high yield in mixed forest, Afforestation provides the theoretical basis.