岷江上游流域植被覆盖度及其与地形因子的相关性

Vegetation Coverage and Its Correlation with Topographic Factors in Upstream Watershed of Minjiang River

[目的]研究岷江上游流域植被覆盖度随不同高程带、坡度带、坡向分布变化的特征及相关性,为该地区利用有利地形加强生态环境建设和防治水土流失提供依据。[方法]在GIS和RS技术支持下,利用Landsat-8OLI遥感影像和DEM数据提取植被覆盖度和地形因子进行叠加分析,构建统计样本定量分析植被覆盖度与地形因子间的相关关系。[结果]研究区总体植被覆盖情况良好,中度以上植被覆盖区占研究区面积75.0%,低植被覆盖区仅占15.2%。植被覆盖度随海拔高度和坡度的增加呈先增加后降低的趋势,在海拔2 500~3 000m和坡度25°~45°达到最大值;阳坡的植被覆盖度略大于阴坡。各地形因子对不同植被覆盖度的影响程度不同,低植被覆盖区受坡度影响较显著,极高度植被覆盖区受海拔高度影响较显著,其他植被覆盖区与地形因子的相关性无明显规律。[结论]岷江上游流域植被覆盖度与地形因子关系紧密,地形因子变化对生态环境有重要影响。

[Objective] By studying the vegetation coverage changes with elevation, slope degree and aspect in upstream watershed of Minjiang River, we aim to provide support for eco-environment improvement and soil erosion control in favorable terrain in the area.[Methods] With the support of GIS and RS, we extracted vegetation coverage and topographic factors from Landsat-8 OLI remote sensing images and DEM data, and then overlaid them. The statistical samples were constructed to analyze the correlation between vegetation coverage and topographic factors.[Results] Firstly, the vegetation coverage in study area was overall in good condition and the area of the medium and above vegetation coverage accounted for 75.0% while low vegetation coverage area is only 15.2%. Secondly, vegetation coverage decreased with the increase of elevations and slopes after the initial increasing, the maximum value ocurred at the elevation of 2 500~3 000 m and the slope of 25°~45°. The vegetation coverage in sunny slopes was slightly higher than that in shady slopes. Lastly, the topographical factors may produced different effects in areas with different vegetation coverage. In areas with low vegetation coverage, the slope degree exerted significant influence while the influence of elevations was significant in areas with extremely high vegetation coverage. There was no significant correlation between other vegetation coverage and topographical factors, which revealed a complex relationship between vegetation and terrains in upstream watershed of Minjiang River.[Conclusion] The vegetation coverage is closely related to the topographic factors in upstream watershed of Minjiang River, and the change of topographic factors has an important impact on the ecological environment.