北京明长城森林景观空间结构的分形特征及稳定性

为了从整体上了解北京明长城沿线森林景观空间结构的分形特征及稳定性状况,基于分形理论,以北京市长城普查数据和近期森林资源调查数据为主要数据源,以北京境内明长城两侧3 000 m 范围内的森林景观为研究对象,在对研究区各景观类型的周长和面积统计的基础上,又对各景观要素类型斑块形状指数及周长-面积的标度和频度关系进行了定量分析,并结合分维数以及稳定性指数对各景观要素类型的分形特征和稳定性进行研究分析。结果表明,研究区内各景观要素类型斑块形状指数以及周长-面积的标度和频度关系是客观存在的。周长和面积统计表明,研究区以有林地和灌木林地为主,二者面积比重之和达83.38%,而疏林地和无立木林地景观面积比重较少,分别为0.76%和0.36%。平均斑块形状指数、分维数以及稳定性指数分析表明,农地和其他用地景观的斑块形状最为不规则,复杂程度最高,空间占据程度最大,稳定性最低,而疏林地斑块形状最规则,稳定性最高。其中,农地景观稳定性指数为-0.086 7,表现为在其复杂形态下的一种稳定性。从整体上看,研究区自然景观斑块形状较人文景观更为规则,稳定性更高。地形地貌和人为干扰是影响景观斑块形状和稳定性的主要因子。 

Fractal characteristics and stability of spatial structure of forest landscape along the Ming Great Wall in Beijing

In order to have an overall understanding of the fractal characteristics and stability of spatial structureof forest landscape along the Ming Great Wall in Beijing, fractal theory was applied in this paper. Thecensus data and recent forest resource survey data for the Beijing Great Wall were used as the main datasource, and the buffer width area of 3 000 m on both sides of the Ming Great Wall as the study object.Based on the statistics data of patch perimeter and area of each landscape type, and the quantitativeanalysis of the relationships between scale and frequency of patch shape index as well as perimeter andarea of each landscape type, the fractal characteristics and stability of each landscape type were analyzedcombining with the fractal dimension and stability index. The results showed that the relationshipsbetween scale and frequency of patch shape index as well as perimeter and area for each landscape type inthe study area objectively exist. The statistics of perimeter and area showed that the study area wasdominated by forest land and shrub land, and the sum proportion of two up to 83.38%, while the areaproportion of open forest land and forest clearings was less, respectively 0.76% and 0.36%. Theanalysis of mean patch shape index, fractal dimension and stability index showed that agricultural landand other landscape types had the most irregular patch shapes, the highest degree of complexity, thegreatest degree of space occupied, and the lowest stability, while the open forest land had the mostregular patch shape and the highest stability. The landscape stability index of agricultural land was-0.087, indicating stability with complex morphology. On the whole, the natural landscape, whencompared to the landscape used by humans, had more regular patch shapes and greater stability.Topography and human disturbance are the major impact factors.