迭部扎尕那林区乔木林景观斑块分形分析

Fractal Analysis on Arbor Forest Landscape of Zha Gana Forest Area in Diebu County

摘要: 在GIS技术的支持下，利用林相图及相关调查资料，采用周长-面积关系的算法对迭部扎尕那林区乔木林景观进行了分形分析。结果表明：1) 乔木林景观类型以针叶林为主，冷杉林面积占乔木林总面积的50.1%，且平均斑块面积较大，分布较为集中完整，是该林区的优势林种。云杉林平均斑块面积水平相对较低，分布较为分散，破碎化程度较高。阔叶林分布面积只占乔木林总面积的9.9%。红桦林是阔叶林中面积最大，分布较为集中的类型。2) 乔木林各林种斑块分维值整体较为接近，介于1.1~1.3之间，说明7种森林类型的斑块边界形状复杂程度相当。不同林种景观斑块分维值大小排列顺序为红桦 < 白桦 < 油松 < 针阔混交 < 针叶混交 < 云杉 < 冷杉。其中阔叶林分维值在1.10~1.15之间，混交林在1.23~1.25之间，针叶林在1.25~1.27之间，基本呈现出面积分布越广、海拔分布范围越高的类型分维数也越高的趋势，一定程度上反映出农田对植被的破坏程度较大。阔叶林中分布面积最大的红桦林分维数最低。3) 扎尕那林区占整个林区乔木林总面积90%的云冷杉林及混交林种基本上是近成过熟林。年龄结构计算的分维数值各龄组之间差别较大。近成过熟白桦林和中龄针阔混交林的分维数接近1.5，斑块形状复杂，且目前处于不稳定状态。中龄红桦林分维值接近1，分布形状最为规则单一，是受农田破坏最大的类型。

Abstract: With the help of GIS technology, the algorithm about the relation of perimeter-area was used to do the fractal analysis of arbor landscape based on the forest map and survey data of Zha Gana Forest in Diebu. The results showed that 1) the type of arbor landscape was dominated by coniferous forest. The area of fir forest accounted for 50.1 percent of the total area of arbor, and its mean patch area was much larger with the centralized and complete distribution. So the fir was superior forest in arbor forest. The level of mean patch area of Picea asperata was relatively low with dispersed distribution and a higher degree of fragmentation. 2) At the whole level, the fractal dimension for each forest was very close, ranging from 1.1 - 1.3. It explained that the shape complexity of seven species of arbor landscape patches were same. The sequence of fractal dimension for different forest landscape patches is Betula albo-sinensis < Betula platyphylla < Pinus tabuliformis < mixed broadleaf-conifer forest < coniferous mixed forest < Picea asperata < Fir. The fractal dimension for the broad-leaved forest ranged from 1.10 - 1.15; the mingled forest ranged from 1.23 - 1.25; and the aciculiailvae ranged from 1.25 - 1.27. There appears a tendency that the wider area and the higher altitude, the higher fractal dimension will be. To a certain extent, it reflected a higher level of destruction of farmland to vegetation. The fractal dimension for Betula albo-sinensis was minimum, which was the biggest distribution area among broad-leaved forest. 3) Accounted for 90 percent of total area of whole arbor forest in Zha Gana Forest, the species of Picea asperata, Fir and mingled forest were essentially mature or over-mature forest. The fractal dimension calculated by age structure was different among various age groups. The fractal dimension for mature or over-mature Betula platyphylla and mid-aged mixed broadleaf-conifer forest was close to 1.5. The shapes of patches were complex and in an unstable state. The fractal dimension for middle- aged Betula albo-sinensis was close to 1. The distribution shape was the most regular and single one; it was the type that suffered the farmland destruction most.