吴起县退耕还林样地土壤粒径分布的单一和多重分形特征

Monofractal and multifractal characteristics of soil particle size distribution in sample sites of Grain for Green in Wuqi County

利用马尔文2000激光粒度分析仪测定土壤粒级体积百分含量,并利用分形理论研究土壤颗粒组成的单一和多重分形特征,以说明陕西省黄土丘陵沟壑区退耕还林工程在减少土壤流失方面的作用。结果表明:荒地和林地土壤黏粒、粉粒体积分数和分形维数(D值)较梯田高,而砂粒体积分数较低。D与黏粒和粉粒体积分数极显著正相关,而与砂粒体积分数极显著负相关。土壤有机质含量与<0.05mm和0.05-1mm体积分数分别存在明显的正相关和负相关关系;与多重分形中的Dq(q≤0)和D1/D0不相关,与Dq(q≥1)显著负相关。林地和荒地土壤粒径分布的Rényi维数谱较梯田土壤的宽。退耕还林还草可使土壤细颗粒物质含量和分形维数增大。在该研究区,土壤细颗粒物质含量和单一分形维数可作为土壤物理性质改善的指标,而Rényi维数谱的相关指标还需进一步提取。

Effects of Grain- for- Green on the soil erosion in gully- hilly regions of the Loess in Shaanxi province were showed by studying monofractal and multifractal of soil particle size distribution using fractal theory.Volume percentages of different sizes were measured by Marvin 2000 laser particle size analyzer. Results showed volume percentages of soil clay and silt and fractal dimension（ D） were higher in waste and forest land than those of terrace land. Volume percentage of sand was higher in terrace land than that of waste and forest land.There were very significant positive relationships between D and volume fractions of clay and silt,significant negative relationships between D and volume fraction of sand. There were positive and negative correlations between soil organic matter content and volume fraction of less than 0. 05 mm and 0. 05- 1. 00 mm respectively. Soil organic matter was uncorrelated to Dq（ q≤0） and D1/ D0 and correlated negatively to Dq（ q≥1）. A Rényi dimension spectrums of PSD in forest and waste lands were wider than those of terrace land. Grain- for- Green could increase content of soil fine particle and D value. In this study area,the content of soil fine particle and D value can be used to indicate improvement of soil physical properties. However,indicators related to Rényi dimension spectra need to be extracted.