不同土地利用方式对黄土高原植被覆盖季节变化的影响--以陕北延河流域为例

植被覆盖是水土流失的重要影响因子,在一定的自然生态背景下,土地利用方式亦決定了植被覆盖特征。为深入探讨植被覆盖季节变化的内在机制,本研究选择地处陕北黄土高原的延河流域,对农地、林地和草地共3种主要土地利用方式,分析其植被覆盖季节变化规律,并进一步对土壤类型和地形特征等生态因子的影响加以比较。研究结果表明,不同土地利用方式下,植被覆盖季节变化产生显著的差异,而相同土地利用方式下,土壤类型的影响最为显著,坡向次之。而影响湿润度的地形特征对植被覆盖的季节变化的影响并不明显。基于上述认识,从改善流域植被覆盖的角度出发,不仅需要通过退耕还林、还草来提升植被覆盖水平,也需配合相应的土壤类型及地形地貌条件改造,才能达到生态格局优化。

IMPACT ON VEGETATION COVERAGE SEASONAL CHANGE OF DIFFERENT LANDUSE TYPES IN LOESS PLATEAU:A CASE OF YANHE BASIN

Vegetation coverage represents the spatial distribution of plant, and is the most important factor for soil erosion. To understand the relationship between vegetation coverage and landuse types, we use Yanhe Basin in Loess Plateau as an example to evaluate seasonal changes of vegetation coverage under different landscape patterns formed by both nature and human activities, such as different soil types and different topographical characters. Moderate-Resolution Imaging Spectroradiometer ( MODIS ) images were used to derive vegetation coverage information calculated with Linear Spectral Unmixing (LSU) based on Mixture Spectral Analysis (MSA). The results are as follows:1)The value range of vegetation coverage in cropland is 6 to 40, in forestland 8 to 49, and in grassland 7 to 45. 2)Landuse types have significant influence on vegetation coverage seasonal change. 3)In the situation of same landuse, soil types have most obvious influence on it, slope aspect take second place, and topographical characters related with wetness index have slight influence. 4)From the aspect of vegetative restoration in catchments, it is not enough to reduce human disturbance and restoration with grass and forest, meanwhile, soil and terrain conditions should be improved to promote the process of ecological pattern optimization.