冀西北清水河流域不同白桦林型土壤分形特征

Soil fractal characteristics of three different forest types of Betula platyphylla in Qingshui river basin of northwestern Hebei Province

为探明不同白桦林型土壤分形维数与土壤质地及土壤理化性质之间的关系,本研究选取冀西北清水河流域白桦(Betula platyphylla Suk)纯林、华北落叶松(Larix principis-ruppredhtii Mayr)×白桦混交林、山杨(Populus davidiana)×白桦混交林3种典型白桦林型,对林下土壤颗粒组成及养分进行测定,利用分形模型比较其土壤颗粒的分形特征,以及分形维数与土壤理化性质之间的关系。结果表明:(1)土壤分形维数介于2.388~2.563之间,3种白桦林型平均分形维数大小排序为:白桦纯林(2.474)>山杨×白桦混交林(2.453)>华北落叶松×白桦混交林(2.423)。(2)土壤分形维数随土层深度的增加呈增长趋势。(3)3种白桦林型林下土壤均为典型的粉砂壤土,土壤分形维数与粉粒和黏粒分别呈极显著与显著的正相关关系,而与极细砂粒则呈显著的负相关关系。(4)分形维数与土壤pH值呈显著正相关关系,而与有机质、全氮、碱解氮、速效磷含量均为极显著负相关关系。针阔混交林(华北落叶松×白桦混交林)分形维数相比其他2种林型较低,土壤养分含量显著高于其他2种白桦林型。因此,土壤分形维数可以作为判断土壤质地与土壤养分差异的指标。

The relationship between soil fractal dimension and soil texture, physical and chemical properties of different Betula platyphylla forest types was investigated in this research.We selected three different types of Betula platyphylla in Qingshui river basin of northwestern Hebei Province to analyze the soil particle composition and soil nutrients of the complex subsoil. Experimental results showed that:(1)The fractal dimension of soil is 2.388-2.563 and the order of soil fractal dimension was Betula platyphylla pure forest(2.474)> poplar birch mixed forest(2.453) and birch mixed forest(2.423).(2)The fractal dimension of soil increased with the increase of soil depth.(3)Three types of birch stand soil were all typical silty loam. The fractal dimension of soil particle size was very significantly and significantly correlated with silt and clay, but negatively correlated with fine sand.(4)The fractal dimension was positively correlated with soil pH value, but negatively correlated with organic matter, total nitrogen,alkali-hydrolyzed nitrogen and available phosphorus content. Compared with the other two forest types, the fractal dimension of coniferous and broad-leaved mixed forest was lower, and the soil nutrient content was significantly higher than that of the other two types of Betula platyphylla forest. The fractal dimension of soil can be used as an index to judge the difference of soil texture and soil nutrients.