山西七里峪油松种群空间格局的分形特征

Fractal properties of spatial pattern of Pinus tabuliformis population in Qiliyu,Shanxi

油松(Pinus tabuliformis)耐低温、干旱和瘠薄,是我国温性针叶林中分布最广的树种,也是我国北方广大地区最主要的造林树种之一。2013年7月,在七里峪林场设置一块100 m×100 m的油松天然林样地,逐一测量并记录了每株油松的胸径、树高和冠幅,并确定它们的坐标位置。应用分形理论中的计盒维数、信息维数和关联维数研究了样地内油松种群空间格局的分形特征。结果表明,油松种群格局具有自相似性,其有较高的计盒维数(1.785)和关联维数(1.826),个体空间相关程度较高,种内竞争激烈,对空间有较强的占据能力。油松种群格局的信息维数较低(0.262),其格局强度尺度变化程度较低,个体分布比较均匀。3个分形维数相辅相承、相互影响,研究结果对全面准确地解释油松种群的空间格局特征具有重要意义。

Pinus tabuliformis is a dominant species in the most widely distributed temperate conif-erous forest community in northern China. The species is resistant to low temperature, dry condi-tions and poor soil nutrient status. It is also one of the most important tree species for forestationin large parts of northern China. In order to study the spatial distribution pattern of P. tabuliformiscommunity, a 100 m xl00 m plot of natural P. tabuliformis stand was established in Qiliyu ForestFarm in July 2013. All trees in the plot were tagged, mapped and measured. The measurementsincluded the diameter at breast height, total tree height and two crown diameters （east-west andnorth-south directions）. The fractal properties of the spatial pattern of P. tabuliformis in the plotwere studied by using the box-counting dimension, information dimension and correlation dimen-sion of fractal theory. The results showed that the high box-counting dimension （1.785） and cor-relation dimension （1. 826） reflected a relatively high degree of individual spatial relatedness,sharp intra-specific competition and powerful spatial occupying of P. tabuliformis population. In-formation dimension of population pattern （0.262） and the scale variation degree of pattern inten-sities were low and the individuals were evenly distributed in space. Three fractal dimensionscomplement and influence each other. These results have important significance for more compre-hensive and accurate interpretation of spatial pattern of P. tabuliformis population.