毛竹种群空间格局的地统计学分析

Geostatistics Analysis on the Spatial Pattern of Moso Bamboo

为了增加对竹林生态系统认识,应用地统计学中的半方差、半方差理论模型模拟、分形维数及其与竹林结构部分因子相关分析,研究毛竹种群空间格局特征。研究结果:(1)毛竹种群半方差总体均值为0.818,林地之间变异较大,属中等强度变异。半方差的标准差较小,占半方差均值的1.293%～7.241%。不同类型毛竹林半方差均值比较两两之间差异不显著。半方差的理论模型模拟多为线性模型,而球状模型和指数模型较少,毛竹林空间自相关性较弱。(2)毛竹林分形维数均趋近于2,表明毛竹林具有较好的均质性。(3)基台值与立竹度、均匀度呈显著相关关系,而分形维数与立竹度和均匀度相关不显著,表明了基台值与分形维数是刻画种群空间格局两方面指标。结论:毛竹林是趋于同质性植被,空间自相关性较弱,毛竹种群半方差在不同类型竹林之间差异不显著;竹林经营时采用竹阔混交林为宜,同时使毛竹在空间分布上趋于均匀,减小半方差,减弱毛竹之间的空间资源竞争强度。

In order to further the understanding of the bamboo ecosystem and serve bamboo management well, the spatial patterns of moso bamboo are explored by analyzing geostatistics and Pearson correlation with partial structure factors of bamboo stand. The results show： i） the mean semi-variance of moso bamboo population is 0.818 with large variation among stands. The standard deviation occupies 1.293%-7.241% of mean semi-variance. There are no significant differences of mean semi-variance among different types of bamboo stands. The semi-variograms of moso bamboo population can be described by linear model mainly and little spherical or exponential model employed, which indicates the spatial self-correlation is poor. ii） The fractal dimension close to 2 indicates that moso bamboo stand tends to homogeneity, iii） Sill correlates significantly with bamboo number per hectare and equality index, but fraetal dimension correlates poorly with them. These reveal that the sill and fraetal dimension are two appropriate indexes in describing spatial pattern. The conclusions are as follows： moso bamboo stand tends to homogeneity and has spatial self-correlation poor. The differences of mean semi-variance are not significant among different types of bamboo stands. So, it is suitable to manage bamboo mixed stand with hardwood, and necessary to decrease the semi-variance and to weaken the competition among bamboo individuals by building possible uniform spatial distribution.