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森林天然更新调查的主要内容有单位面积幼树的数量及更新频度两项。这两项调查,通常是结合在一起进行的,即在林内系统设置许多方形、长方形、圆形的小样方(圆),分别树种、树高级查数小样方中的幼树。由于幼树分布不均,在成长过程中还要不断地自然稀疏,因此,只有株数的概念还是不足的,这时,频度可以作为反映幼树均匀程度的相对性指标。但频度这一指标还不能形象地反映出幼树的空间分布状况。同时,单位面积内的幼树株数和频度,这两个指标还确定不了应该补植的面积及幼树团内应该间伐的强度。
The main contents of the forest natural update survey are the number of saplings per unit area and the update frequency of two. The two surveys are usually carried out in conjunction with the system, that is, a number of square, rectangular, round sample square (circle), set tree species, tree high-grade small trees in the forest system. Because of the uneven distribution of saplings, they are still naturally sparse in the growth process. Therefore, only the concept of the number of trees is still insufficient. In this case, the frequency can be used as a relative index reflecting the uniformity of young trees. However, the frequency of this indicator can not be an image to reflect the spatial distribution of saplings. At the same time, the number of young trees per unit area and frequency, these two indicators also can not determine the area should be replanted and saplings should be thinning intensity.