天童常绿阔叶林林窗的地形分布格局

Topographic distribution patterns of forest gap within an evergreen broad-leaved forest in Tiantong region of Zhejiang Province,Eastern China

为探究多维地形因素对林窗分布的影响,以天童20hm2常绿阔叶林动态监测样地内的林窗为对象,结合地理信息系统软件,分析了林窗空隙率、林窗密度以及林窗面积在海拔、坡度、坡向、坡形、坡位5种地形因子下的分布格局.结果表明:该样地林窗空隙率为13.1%,林窗密度为9.5个·hm-2,林窗平均面积为137.82m2;因高海拔台风干扰的强度较大,高海拔段(≥500m)林窗的空隙率和密度显著大于中低海拔段(<500m);台风带来的强降雨极易引起小范围滑坡,使得沟谷的林窗空隙率和密度显著大于侧坡,林窗平均面积显著大于侧坡和山脊.台风及其带来的强降雨是造成林窗在海拔及坡位梯度上具有显著性差异的主要原因.

To explore the effects of multi-dimensional topographic factors on forest gap distribution, the forest gaps in a 20 hm2 dynamic monitoring plot of an evergreen broad-leaved forest in Tiantong region of Zhejiang were taken as the objects to study the distribution patterns of the gap fraction, gap density, and gap area under the effects of altitude, slope degree, slope shape, slope aspect, and slope position by using a geographic informtion system （GIS） software. In the plot, the gap fraction was 13.1%, gap density was 9.5 ind . hm-2, and average gap area was 137.82 m2. Be- cause of the greater intensity of typhoon disturbance at high altitudes, the gap fraction and gap den- sity at the high altitude （ ≥500 m） sections were significantly larger than those at the medium and low altitude （〈500 m） sections. The heavy precipitation produced by typhoon could easily cause small scale landslide, and thus, lead to the gap fraction and gap density being larger in valley area than in side-slope and ridge. It was suggested that typhoon and its produced heavy precipitation could be the main causes of the significant differences in the forest gaps along the gradients of alti- tude and slope position.