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森林生产力可以由独占圆推导的原则所优化 ,独占圆是以林木为圆心 ,以其邻体距离的 1/ 2为半径所画的圆。已经证明独占圆有如下 3个特性 :(1)独占圆之间不会重叠 ,最近的关系是相切 ;(2 )完全均匀分布格局的独占圆总面积与植物株数无关 ,而且是样地总面积的 2倍 ;(3)从样地上去掉一株植物 ,只会增大某些独占圆的面积 ,而不会减少其它独占圆的面积。定义均匀度 (L )为 :样地上的独占圆总面积除以完全均匀格局的相同样地上的独占圆总面积。均匀度 (L )服从分布 :L～ x2 (2 n) / 2πn,且有E(L) =1/ π=0 .318,L 的方差 D(L) =1/ nπ2 ,可见 E(L)与 n和样地面积均无关 ,L 是一个相对指标。 L 可以用于对格局类型的检验。“增面积林木”定义为 :去掉它可以增加独占圆总面积的林木。第二邻体距离大于第一邻体距离 2倍的林木就是增面积林木 ,这就是所谓 2原则。在所调查的样地上 ,随意性地将样地分成 6块 ,在每块样地上其增面积林木的比例均约为 1/ 2 ,无一例外。在随机格局的假设下 ,推导了 6块分割样地的增面积林木的期望比例 ,其值为 0 .35～ 0 .4 4。显然 ,期望值与抽样值的差异明显 ,而引起差的原因尚难以解释 ,有待进一步研究。提出了在择伐中增加林地均匀度的两条原则 :(1)独占圆面积偏小 ;(2 )增面积林
Forest productivity can be optimized by the principle of exclusivity, which is a circle drawn from a forest centered on ½ of its neighbor’s distance. It has been proved that the exclusive circle has the following three characteristics: (1) exclusive circle will not overlap, the recent relationship is tangent; (2) completely uniform distribution of the total area of the exclusive circle has nothing to do with plant number, Area of 2 times; (3) Remove a plant from the sample will only increase the area of some exclusive circle, without reducing the other exclusive circle area. The defined uniformity (L) is the total area of the exclusive circles on the same plot of land divided by the total area of the same plot of perfectly uniform patterns. (L) = 1 / nπ2, we can see that E (L) is the distribution of L: x2 (2n) / 2πn and E (L) = 1 / π = Regardless of n and plot area, L is a relative indicator. L can be used to verify the pattern type. “Increased area of forest” is defined as: Remove it can increase the total area of the exclusive circle of trees. The second neighbor distance greater than 2 times the distance between the first neighbor forest is increased area of forest, which is the so-called 2 principle. On the plots under investigation, the plots were randomly divided into six plots, each of which had about one-half of the area of increased forest area on the plot, without exception. Under the assumption of stochastic pattern, the expected proportion of increasing area trees in 6 plots was deduced, and the value was 0.35 ~ 0.44. Obviously, the difference between the expected value and the sampling value is obvious, and the reason of the difference is still difficult to explain and needs further study. Proposed two principles of increasing woodland evenness in selective cutting: (1) the area of exclusive circle is small; (2)