沂蒙山区土壤侵蚀垂直景观格局的分形特征

    Fractal characteristics of vertical landscape of soil erosion in the Yimeng mountainous area

    • 摘要: 以北方土石山区的典型代表沂蒙山区为研究区,以TM影像和地形图为源数据,根据全国土壤侵蚀分类分级标准,综合运用GIS和RS技术,获取以50 m为带宽的土壤侵蚀强度垂直分带数据。在Fragstats3.3中提取周长面积分维数(D),计算稳定性指数(SI),旨在揭示沂蒙山区土壤侵蚀分形的垂直变化特征。结果表明,土壤侵蚀景观在垂直维度上具有明显的分异性。在景观水平上,土壤侵蚀景观周长面积分维数(D)随高程呈先迅速增大后缓慢增大趋势,稳定性指数(SI)则呈先急剧减小后缓慢减小趋势。在缀块类型水平上,对于研究区,D值在土壤侵蚀等级上由大到小顺序为中度>轻度>强烈>极强烈>剧烈>微度,SI值由小到大的顺序为轻度<强烈<中度<极强烈<剧烈<微度;随着高程的增加,微度、强烈、极强烈和在较低高程带(≤200带)上的轻度侵蚀景观,D值增大,SI值减小;剧烈和较高高程带上的轻度侵蚀景观,D值与SI值呈减小趋势;较高高程带(>200带)上的中度侵蚀景观,D值与SI值呈增大趋势;表明,人类活动对较高强度(强烈和极强烈)侵蚀景观的格局及其稳定性相比自然因素具有较高的决定性;在较高海拔带,较低级别(中度和轻度)的侵蚀景观格局及其稳定性受自然因素影响较大。

       

      Abstract: Taking the Yimeng mountainous area, one of the most representative area of the Rocky Area of Northern China, as a case study, according to the Standards for Classification and Gradation of Soil Erosion (SL190-2007), supported by the technology of GIS and RS and the data of Landsat TM image and relief map, this study aimed to explore the fractal characteristics of the vertical landscape of soil erosion in the Rocky Area of Northern China. The vertical landscape of soil erosion was divided to 16 belts with the elevation range of 50 m. The perimeter-area fractal dimension (D) was calculated by the software of Fragstats ver 3.3, and the landscape stability index (SI) was obtained form D. The results showed that there was obvious variability of the soil erosion landscape in vertical dimension. In the landscape level, D increased dramatically at first and then slightly, while SI decreased quickly at first and then slowly. In the class level, as to the whole study area, the sequence of D values of the soil erosion intensity types from large to small was that of moderate, slight, intense, very intense, sever and minimal. And the sequence of SI was that of minimal, sever, very intense, moderate, intense and slight. With elevation rising, the D value of the soil erosion intensity type of minimal, intense, very intense and the slight in higher elevation tended to increase and the SI vice versa. As to the D and SI of the slight and sever type, the values inclined to reduced, while to the moderate type on the higher elevation, D and SI tended to increase. These indicated that in the lower elevation areas, the human activities disturbed landscape pattern and stability further than natural factors on the higher (intense and very intense) soil erosion intensity landscape types. While in the higher areas, the pattern and stability of the lower (moderate and slight) soil erosion intensity landscapes were impacted greater by natural factors.

       

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