地形对天然次生林空间格局的影响

Influence of Topography on Vegetation Pattern in Secondary Forests

利用数字化地形模型(DEM)与景观类型图进行地理信息叠加,以定量化地反映主要群落在不同坡度、坡向以及坡位的空间分布,获得各群落的分布结构,数量化研究地形因素与植被分布的关系。在Arcgis及其3D和空间分析扩展模块的支持下,计算并探讨了老爷岭天然次生林主要树种(蒙古栎、榆树、水曲柳、胡桃楸等)在地形因子(坡度、坡向、坡位)各梯度级的分布比重及分布情况。结果表明,研究范围内样方的坡度在10．2°一22．5°之间。坡向分为5个等级,坡度及坡向差异显著。对坡度、坡向等地形因素及群落的物种组成进行半方差分析,发现三者的空间异质性尺度分别为31．2、161．6、17．3。地形因素的变化尺度远大于植被组成的变化,说明小尺度下地形因素不是影响群落内种群分布格局的唯一因素。坡度和坡向因子的块金值分别为9610及2 172,说明两者在小尺度下的某些过程不能忽视。植物与地形因素的相关分析表明,不同的种对地形的适应性有差异,群落中的9种主要植物可以分为4个生态种组。因此,群落的物种组成变化受到多种因素的影响,这种影响可以在地形变化中得到反映。

Superposition of geographic information of the digital elevation model （DEM） and maps of landscape genres is weighed to mirror the spatial distribution of the plant communities at different slops, aspects and position. Then a quantified correlation between topographic factors and plant distribution was gained through the structure of this spatial distribution of the plant communities. The proportions of the main tree species （ Quercus mongolica, Ulmus pumila, Fraxinus mandshurica, Juglans mandshurica） at different grades of the topographic factors （slope, aspect and position） in the secondary forests in the region of Laoyeling were calculated with the help of modules of Aregis, 3D and the extend module of spatial analysis, and the distribution of these tree species was discussed. Result indicated that the average slope of the plots is between 10.2° and 22.5° in the research area. There are five levels for the slope aspect, and marked differences are showed in slope and aspect. The scales of the spatial heterogeneity are 31.2, 161.6 and 17.3 m, respectively, according to the semi variance analysis of topographic factors such as slope and aspect as well as species composition of the plant community. The scale of topographic factor is much larger than that of the species composition, which demonstrates that topographic factor is not the only factor influencing the species composition of the plant community in small scale. The nugget variance of semi variance of slope and aspect are 9 610 and 2 172, which indicates that the influence of topographic factor in small scale cannot be ignored. The topographic adaptation of these species is different, and according to their respect to topography, these nine species are classified into four groups using hierarchical cluster analysis. Therefore, the species composition of a community is affected by a variety of factors, and this effect can be reflected by the variety of topography.