砒砂岩沟坡沙棘群落冠层结构特征及密度调控思考

在砒砂岩区沙棘人工群落中,沙棘层鲜重平均占89%,草本层占11%。沙棘标准株鲜重生物量随树高分布模型为Cubic模型,即最下层生物量较小,向上增加很快,然后随着高度上升,生物量逐渐减少。对于2a、4a、6a、8a、10a等5个林龄,沙棘枝干鲜重的主要分布层次分别为0-40cm、0-120cm、0-140cm、0-160cm、0-210cm,即枝干重量随林龄的增加而不断向上延伸;而叶鲜重的主要分布层次分别为20-70cm、60-140cm、70-180cm、60-190cm、120-230cm,叶重量也随林龄的增加,其聚集重心部位不断向上转移。生产实践中应通过调节密度（如带状间伐）等,使叶的分布层次下移,这样将有利于沙棘果、叶的采摘,同时,也能防止由干旱而造成的沙棘枯死或感染病虫害而致死亡。

Thinking on Canopy Structure and Forest Density Regulation of Seabuckthorn Community in Soft Sandstone Area

The wet weights of seabuckthorn layer and grass layer occupy respectively 89% and 11% of the total wet weight of the community of seabuckthorn.The models of wet weight of seabuckthorn with height are mostly cubic,that is,with a small biomass in the near ground layer,a higher biomass in the middle height and small biomass again in the upper layer of the tree.For the forest ages of 2a,4a,6a,8a,10a,the wet weights of the stem and branches distribute mainly（80%） in the layer of 0~40cm,0~120cm,0~140cm,0~160cm and 0~210cm respectively,whereas those of the leaves in the layer of 20~70cm,60~140cm,70~180cm,60~190cm and 120~230cm respectively.In the practice of seabuckthorn planting,the forest densities should be regulated with belt cutting,etc.,to not only lower the leaves distribution for the picking of leaves and fruits,but avoid the deaths both from the drought and diseases in the area.