青海云杉(Picea crassifolia)种群格局的分形特征及其影响因素

Characteristics in Picea crassifolia forest fractal dimension and its influencing factors

应用计盒维数、信息维数和关联维数对祁连山主要森林类型青海云杉（Picea crassifolia）种群空间格局进行的研究表明：青海云杉种群格局计盒维数在0.992～1.938之间,平均值为1.716,信息维数在0.996～1.860之间,平均值为1.632,关联维数在1.418～1.759之间,平均值为1.568。计盒维数与样地海拔和土壤水分含量呈显著的负相关,与样地坡向呈显著的正相关,信息维数与样地海拔呈显著负相关而与坡向呈显著的正相关,关联维数与样地坡度呈显著的负相关,主成分分析表明,海拔和土壤含水量是影响青海云杉种群格局分形维数第一主成分,坡向是第二主成分,坡度是第三主成分,这3个主成分累计解释率为87.6%。

The objective of this study is to analyzes the scale variation and the spatial patterns of Picea crassifolia populations in Qilian Mountains, using box-counting dimension, information dimension and correlation dimension, and to identify the relationships between the spatial pattern and some selected environmental factors. Sixteen plots （20m～ 20m） with different elevation in Picea crassifolia forest of QiLian Mountains were investigated to calculate fractal dimensions, and some selected environmental factors （elevation, slope degree, slope direction, soil depth , soil bulk density , soil organic carbon, total nitrogen, soil water content） were measured. The results shows that the values of box-counting dimension, information dimension and correlation dimension of pattern of Picea crassifolia populations ranged from 0. 992 to 1. 938, 0. 996 to 1. 860 and 1. 418 to 1. 759, and its average value is 1. 716, 1. 632 and 1. 568, respectively. Box-counting dimension is negatively correlated with elevation and soil water content, while positively correlated with slope direction. Information dimension negatively correlated with elevation, but positively correlated with gradient. Correlation dimension negatively correlated with slope direction. The principal component analysis shows that elevation and soil water content are the first principal component affecting fractal dimension, followed by slope direction and slope degree, which accounts for 83.8% of the varianee of fraetal dimension.