论文部分内容阅读
乌兰布和沙漠东缘防风固沙基干林带始建于50年代初,以后又不断补植加宽。迄今林带总长达152.49公里,最大宽度2300米,最小宽度30米。现有林面积3639.48公顷,其中柳树2060.55公顷,占有林总面积的56.6％。近年来,林带内的柳树大面积枝梢枯死,严重影响了林带的防护效益。1978年5月,通过对整个林带近20个点的调查,柳树化梢主要有以下原因。 1、老枝条造林。据调查,50年代初期营造的柳树林带,所用苗条大部分从宁夏平罗一带成林柳树上采取。枝条年龄较大,造林后生命力弱,生长衰退,导致枯梢。由于采
The windbreak and sand-fixation trunk belt of the Ulan Buh Desert and the eastern edge of the desert was first established in the early 1950s and has been continuously replanted and widened. So far the total length of 152.49 km forest, the maximum width of 2300 meters, the minimum width of 30 meters. The existing forest area of 3639.48 hectares, of which 2060.55 hectares willow, accounting for 56.6% of the total area of forest. In recent years, large areas of willow trees in the forest belt withered, seriously affecting the protection effectiveness of the forest belt. May 1978, through the investigation of nearly 20 points throughout the forest, willow tree shoots mainly for the following reasons. 1, old branches afforestation. According to the survey, the willow forest belt created in the early 1950s was mostly taken from the willow trees in Pingluo, Ningxia. Olive branches, afforestation, weak vitality, growth recession, leading to shoots. Due mining