清江流域生态系统植被不同林分因子随海拔梯度的变化

Stand Factors of Qingjiang River Basin along the Altitudinal Gradient in Different Longitudes

选择清江流域的南部和北部进行垂直样带调查,将2个调查地段分别等距离划分为高、中和低3个海拔区域,研究林分因子在不同海拔范围内的差异,并比较2个地段林分因子随海拔梯度变化的总体趋势.结果表明:2个地段的林分因子随海拔梯度的变化呈现不同的变化格局.在南部,林分因子(平均胸径、最大胸径、平均树高、最大树高、胸高断面积和蓄积量)随海拔的增加逐渐下降;在北部,林分因子(平均胸径、最大胸径、平均树高、最大树高、胸高断面积和蓄积量)随海拔梯度的变化呈单峰型变化趋势.尽管相同的林分因子在两个地段呈现不同的变化格局,但两个地段林分因子的变化都可以用二次曲线方程y=ax2+bx+c(a、b、c为常数)进行描述.

The vertical sample str/ps of Southern and northern in Qingj＇iang River Basin were investigated. Each site was divided into three altitudinal ranges （high,middle and low） and the difference in stand fac- tors within each site range was analyzed.The variation of main stand factors along the altitudinal gradient was investigated. The results showed that variation of different stand factors within each site presented dif- ferent patterns. In the southern, the stand factors （mean and maximum DBH, mean and maximum tree height, total basal area and stand volume） gradually deereases with the increase of altitude;in the north- ern,the stand factors showed hump- shaped curves with increasing of the altitude. Although the same stand factors in the two areas present different change pattern, the stand factors in the two areas could be described by the quadratic curve equations y = ax2 ＋bx ＋c （ a, b, c for constant）.