不同耕作年限水稻土土壤颗粒的体积分形特征研究

应用基于土壤颗粒体积分布确定土壤颗粒大小分布分形维数的方法,对浙江慈溪耕作年限分别为50、100、500、700、1000和2000年的水稻土土壤颗粒体积分形特征进行了研究.结果表明:同基于土壤颗粒质量分布的分形维数相比,基于土壤颗粒体积分布的分形维数计算不需要密度假设,更具有合理性.不同年限水稻土的土壤颗粒大小分布能被体积分形模型显著拟合(p＜0.01).土壤颗粒体积分形维数与黏粒的体积百分含量之间呈显著正相关(p＜0.01),与粉粒和砂粒的体积百分含量之间呈显著负相关(p＜0.01),其中与黏粒含量关系最为密切.耕作年限对水稻土土壤颗粒的体积分形维数和分形模型的拟合度均有一定影响.与50 ～ 500年水稻土相比,700 ～ 2000年水稻土剖面中土壤颗粒体积分形维数的变异性和均值较高,但其拟合决定系数则较低;耕作年限会对水稻土剖面中黏粒的含量和分布产生影响,进而影响到剖面土壤的颗粒体积分形特征;对于同一质地类型的土壤,耕作年限越长,分形维数越高.

Volume Fractal Property of Soil Particle Size Distribution of Paddy Soils Cultivated for Different Years

Fractal dimension of soil particle size distribution (PSD) was calculated by a method on the basis of accumulative volume distribution of soil particles. Fractal properties of PSD in profiles of paddy soils sampled from Cixi City of Zhejiang Province were investigated with the new method, and rice-cultivation ages of these paddy soils were 50, 100, 500, 700, 1000 and 2000 years, respectively. Results showed that the volume fractal dimension of PSD was more reasonable and credible than the mass fractal dimension of PSD. The PSD of paddy soils cultivated for different years could be significantly fitted by the volume fractal model (p<0.01). The volume fractal dimension of soil particles was in significantly positive correlation with the volume percentage of soil clay (p<0.01), and in significantly negative correlation with the volume percentage of silt and sand (p<0.01). Compared to silt and sand, the effect of soil clay content on the volume fractal dimension of PSD was more remarkable. Cultivated age had some influence on volume fractal dimension of paddy soils and fitness of the fractal model. Variability and mean of volume fractal dimension of soil particles in profiles of paddy soils cultivated for 700 ~ 2000 years were higher, and determination coefficient of their fitting models was lower, as compared with paddy soils cultivated for 50 ~ 500 years. Cultivation age could influence fractal property of soil particles in soil profiles through changing distribution of clay content. Fractal dimension of paddy soils with the same texture increased with increasing cultivation age.