华北落叶松人工林树高和胸径的坡位差异与坡面尺度效应——以六盘山香水河小流域为例

Slope variation and scale effect of tree height and DBH of Larix principisrupprechtii plantations along a slope: A case study of Xiangshui watershed of Liupan Mountains

在六盘山香水河小流域选择了一个水平长398.2 m和生长33年生华北落叶松人工林的典型坡面,调查分析了华北落叶松胸径与树高的坡位差异及随坡面水平长度变化的空间尺度效应。结果表明:(1)林分的胸径和树高都存在明显的坡位差异,从坡顶向下均表现为先增加后减小的变化趋势。(2)林分平均胸径、平均树高、优势木平均高均存在坡面尺度效应,即平均胸径的坡面滑动平均值在离开坡顶的0~200 m和200~398 m的水平距离范围内每增加100 m时增大0.33 cm和减少0.21 cm;平均树高的滑动平均值在0~67、67~305、305~398 m的水平距离范围内每增加100 m时分别减少1.12 m、增大0.31 m、减少0.10 m;优势木平均高的坡面滑动平均值在0~250 m、250~398 m的水平距离范围内每增加100 m时增大0.42 m和0.07 m。(3)各样地的平均胸径、平均树高、优势木平均高与坡面加权平均值的比值(Y_1、Y_2、Y_3,小数)随离开坡顶相对水平坡长(X,小数)变化的数量关系为:Y1=-0.312 8X2+0.239 1X+0.986 4(R^2=0.56)、Y_2=-0.483 4X3+0.304 3X2+0.125 0X+0.959 2(R^2=0.43)、Y_3=-0.177 5X^2+0.230 8X+0.941 6(R^2=0.26),藉此可由特定坡位的样地调查值推算整个坡面平均值,实现树木生长指标从样地到坡面的尺度转换。

This paper selected a representative slope with a horizontal length of 398.2 m and covered by 33 years-old Larix principisrupprechtii plantation in the small watershed of Xiangshuihe of Liupan Mountains, the variation of tree height and DBH along the slope length and their scale effect were investigated and analyzed. Results showed that：（1） Both the DBH and tree height presented a changing tendency of firstly increase and then decrease along the slope from top to foot.（2） The regression relations showing the variation of the moving averages of mean DBH, mean tree height and mean height of dominant trees with increasing horizontal distance from slope top were fitted. With these relations, the slope scale effect of the three growth parameters was calculated. With a 100 m increase of the horizontal distance downwards, the moving average of the stand mean DBH increased by 0.33 m in the horizontal distance range of 0~200 m, and decreased by 0.21 m in the range of 200~398 m; the moving average of tree height decreased by 1.12 m in the range of 0~67 m, increased by 0.31 m in the range of 67~305 m, and decreased by 0.10 m in the range of 305~398 m; the moving average of the height of dominant trees increased by 0.42 m in the range of 0~250 m, and increased by 0.07 m in the range of 250~398 m.（3）The relations were fitted to express the slope variation of the ratios of the plots means of DBH, tree height and the height of dominant trees（Y_1, Y_2, Y_3, decimal） to their slope average with the relative horizontal distance from slope top（X, decimal）： Y_1=-0.312 8X^2＋ 0.239 1X＋0.986 4（R^2= 0.56）, Y_2=-0.483 4X3＋0.304 3X2＋0.125 0X＋ 0.959 2（R^2= 0.43）, Y_3=-0.177 5X^2＋0.230 8X ＋0.941 6（R^2 = 0.26）. Using these relations, the whole slope averages of stand growth parameters can be calculated based on the measured values of a plot with a certain slope position, and the up-scaling of stand growth parameters can be realized.