山西太岳山白桦种群结构和空间分布格局

Betula platyphylla population structure and its spatial distribution pattern in Taiyue Mountain of Shanxi,China

白桦(Betula platyphylla)林是山西太岳山地区的常见植被类型之一。根据太岳山白桦林不同林龄结构设置3个典型样地,采用空间差异代替时间变化的方法,运用点格局和分形分析(计盒维数、信息维数和关联维数),对太岳山白桦种群结构以及不同发育阶段种群空间分布规律进行了探讨。结果表明:太岳山白桦种群径级结构呈典型的"纺锤"型,属于衰退型种群;在0~25 m内白桦种群以幼树、中龄树为主时呈聚集分布,而成熟树占多数时呈随机分布,即随着种群年龄的增加,呈现聚集分布向随机分布的转变;白桦种群空间占据程度为中龄林>成熟林>近熟林;白桦种群格局强度尺度变化程度为近熟林>中龄林>成熟林;白桦种群个体空间关联程度为中龄林>成熟林>近熟林。种群径级结构分析、点格局分析和分形分析结果一致,揭示了地带性顶极群落破坏后兴起的次生先锋群落的空间分布格局。

Betula platyphylla forest is one of the major vegetation types in Taiyue Mountain of Shanxi,China. Our objective was to explore B. platyphylla population structure and its spatial distribution pattern in this region. Three plots were established according to the diverse age structures of the B. platyphylla population. The B. platyphylla population structure and its spatial distribution at different developmental stages were examined by means of the ＂space-for-time＂substitution approach. The point pattern and fractal analyses including box-counting dimension analysis,information dimension analysis,and correlation dimension analysis were used in this study. It was found that the diameter-class structure of the B. platyphylla population indicated a typical＂spindle＂shape,suggesting a declining trend. The young and middle B. platyphylla population was found to show an aggregated distribution pattern,whereas the mature one exhibited a random distribution pattern. It was suggested that along with population development,the spatial distribution of B. platyphylla population varied from aggregation to randomness. The analysis of boxcounting dimension indicated that the degree of the occupied space of B. platyphylla population followed an order of middle-aged trees〉mature trees〉near-maturity trees. The analysis of information dimension indicated that the changing degree of pattern intensity of B. platyphylla population followed an order of near-maturity trees〉middle-aged trees〉mature trees. The analysis of correlation dimension showed that the individual spatial correlation of B. platyphylla population followed an order of middle-aged trees〉mature trees〉near-maturity trees. It was suggested that there were consistent results from population diameter-class structure analysis,point pattern analysis and fractal analysis. All these results revealed the spatial distribution pattern of secondary pioneer community after the destruction of the zonal climax community.