石羊河林业总场从建场以来,采用机械植树的方法营造起沙枣防护林19万多亩。据营林规划调查资料,到1980年实际保存面积17.7万亩,已衰退枯死的沙枣林有21100多亩。但保存下来的沙枣人工林,多有沙枣木虱、沙枣尺蠖等害虫的严重危害,普遍生长不良。有关方面对此十分关注,科研单位也有人对沙枣人工林的衰退做过研究,认为地下水位下降、生态条件恶化,林地土壤干燥,林木缺水所致。据我们十多年来的观察:认为沙枣人工林衰退的原因是多方面的,如造林密度大,经营管理赶不上去,虫害严重等。当然有一部分沙枣林的死亡,确是因地下水位下降所致。但是有些地方的沙枣林死亡,是经营管理问题,在那里并不 Shiyanghe forestry total field Since the establishment of the site, the use of mechanical tree planting method to create sand jujube shelter 190,000 mu. According to the survey data of the planning of the forest, by 1980, the actual preserved area was 177,000 mu, and there were 21,100 mu of jujube forest which had died down. However, the preserved dates of plantation, there are more jujube psyllids, sand jujube and other pests serious harm, the general poor growth. Concerned parties are very concerned about this. Some people in scientific research institutes have also studied on the decline of Eucalyptus Jujube plantation and think that the groundwater level is declining, the ecological conditions are deteriorating, the soil in the forest land is dry and the water shortage of trees is caused. According to our observations for more than a decade, the reason for the decline of stem jujube plantations is due to many factors, such as the density of afforestation, the inability to keep up with management and the serious pests. Of course, part of the jujube forest death, indeed due to the decline of groundwater levels. However, in some areas, the death of jujube forest is a management problem that is not there