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以重庆缙云山次生林典型针阔混交林、常绿阔叶林、毛竹林、灌木林及农地(对照)的土壤为研究对象,应用分形模型研究了各林地土壤A、AB、B、C层土壤团粒分形特征,探讨了团粒分维、团粒质量几何平均直径与土壤理化性质和土壤养分含量等肥力特征之间的关系。结果表明:(1)各林地土壤团粒分维在2.348~2.834之间,表现为针阔混交林<灌木林<常绿阔叶林<毛竹林<农地(对照),团粒分维反映了团聚体含量、结构破坏率和质量几何平均直径的状况;(2)针阔混交林土壤酸性最强,通气性和持水性最优,土壤养分含量表现为阔叶林>灌木林>混交林>农地(对照)>毛竹林,毛竹林土壤肥力水平最低;随着土壤深度增加,各项土壤肥力指标均呈下降趋势,与团粒分维变化趋势相反;(3)土壤团粒分维与土壤容重呈正相关,与通气孔隙、毛管孔隙、最大持水量、土壤养分含量和阳离子交换量呈负相关,而团粒质量几何平均直径与其关系恰好相反。土壤团粒分维与质量几何平均直径可表征长江上游林地土壤各层团粒特征,且能反映土壤肥力水平,可作为评价土壤肥力的一个重要指标。
Taking the typical secondary coniferous and broad-leaved mixed forest, evergreen broad-leaved forest, moso bamboo forest, shrub forest and farmland (control) as the research objects in the secondary forest of Jinyun Mountain in Chongqing, the fractal model was used to study the soil layers A, AB, B and C The relationship between the fractal dimension of aggregate, the geometric mean diameter of aggregate mass, soil physico-chemical properties and soil nutrient content and other fertility characteristics were discussed. The results showed as follows: (1) The fractal dimensions of soil aggregates in each forest ranged from 2.348 to 2.834, which were mixed coniferous and broadleaf forest evergreen broad-leaved forest shrub forest> mixed forest> agriculture (Control)> Phyllostachys pubescens forest and Phyllostachys pubescens forest had the lowest soil fertility. With the increase of soil depth, the indexes of soil fertility showed a downward trend, which was contrary to the fractal dimension of the aggregates. (3) The fractal dimension of soil aggregates and soil bulk density were positive , But negatively correlated with aeration porosity, capillary porosity, maximum water holding capacity, soil nutrient content and cation exchange capacity, while the relationship between the geometric mean diameter of aggregate mass and its correlation was just the opposite. The fractal dimension of soil aggregates and the geometric mean diameter of soil mass can characterize the aggregate characteristics of forest soil layers in the upper reaches of the Yangtze River and reflect the soil fertility level, which can be used as an important index to evaluate soil fertility.