吉县蔡家川流域不同树龄刺槐林和油松林土壤微团聚体分形特征研究

本研究以山西吉县蔡家川流域内不同树龄的刺槐、油松纯林及其撂荒地为研究对象,应用Microtrac S3500激光粒度分析仪,对各地类土壤剖面中8个层次168个土壤样品的微团聚体组成进行测定后,利用分形几何学方法分析了土壤微团聚体的分形特征。结果表明:土壤微团聚体体积分形维数D随土层深度增加呈现递减趋势,平均值为2.22,变化于1.75~2.7之间。各地类土壤微团聚体体积分形维数D与<0.005 mm粒级土壤微团聚体体积分数呈极显著正相关关系,相关系数R均大于0.95,与其它粒级土壤微团聚体体积分数相关性不显著。根据土壤养分状况、土壤物理性质与土壤微团聚体分形维数成反比的研究结论,各地类0~20 cm深度土层的肥力状况和物理性质较20~40 cm土层好,撂荒地土壤肥力状况和物理性质最差,刺槐林地的肥力状况和物理性质好于油松林地,随着树龄的增加,土壤肥力和物理性质有下降趋势。

Study on Fractal Features of Soil Micro-aggregates Under the Robinia Pseudoacacia and Pinus Tabulaeformis of Different Ages in Caijiachuan Watershed of Ji County

Using forest of Robinia pseudoacacia and Pinus tabulaeformis of different ages and their abandoned lands in Caijiachuan watershed,Ji County,Shanxi Province as the objects,168 soil samples in 8 soil layers of the three different land types are measured with S3500 Laser Granularity Analyzer.And the fractal characteristics of soil micro-aggregates are analysed through geometrical methods.The results show that the volume fractal dimension(D) of soil micro-aggregates turns out a downward trend along with increasing depth of soil,and it varies from 1.75 to 2.7 with an average of 2.22;on one hand the volume fractal dimension(D) of soil microaggregates of all the three land types has a highly significantly positive correlation with the volume fraction of <0.005 mm soil micro-aggregate,and the correlation coefficients are all more than 0.95;on the other hand,it has no significant correlation with the volume fraction of other size fraction soil micro-aggregates.The soil fertility and physics property of 0-20 cm soil layer are both better than those of 20-40 cm soil layer in all the three land types;the soil fertility and physics property of Robinia pseudoacacia are both better than those of Pinus tabulaeformis,and those of the abandoned land are the worst.The soil fertility and physics property show a decreasing tendency with the increase of tree ages,and soil nutrient status and physics property are inversely related to the volume fractal dimension(D) of soil microaggregates.