黄土丘陵区典型植被土壤剖面的颗粒分形特征

运用分形理论研究陕北安塞五里湾流域5种典型植被0～200 cm土壤剖面土壤颗粒大小分布(particle size distribution,PSD)及其体积分形维数分布特征,并进一步分析土壤PSD的分形维数与土壤有机碳、全氮和含水量的相关性。结果表明:研究区典型植被群落土壤颗粒组成主要为细颗粒(黏粒和粉粒),其中粉粒体积分数占总颗粒的56.82%～71.99%;铁杆蒿草地的细颗粒平均体积分数最大(78.86%),乔木林的最小(65.77%)。5种典型植被群落土壤PSD的体积分形维数介于2.498～2.599,均表现出随着土层深度的增加呈递增趋势;相同土层深度的分形维数呈现出铁杆蒿草地黄芪草地农田灌木林乔木林的趋势,灌木林和农田间差异不显著,其他植被群落间差异显著。典型植被土壤PSD的体积分形维数与黏粒、粉粒的体积分数和含水量呈极显著正相关(P0.01),但与砂粒的体积分数呈极显著负相关(P 0.01),与有机碳含量呈显著负相关(P 0.05)。

Fractal Characteristics of Soil Particle Compositions in Soil Profiles of Typical Vegetation Types on Loess Hilly Region

Based on fractal theory, the fractal characteristics of soil particle size distributions (PSDs) within 0-200 cm soil profiles of the typical vegetation types in Wuliwan Watershed on the Loess Hilly Region were studied to explore the effects of vegetation type and soil depth on soil structure and to explore the relations between the volume fractal dimension and the contents of soil organic carbon, total nitrogen and soil water. The results showed that soil particle composition was mainly fine particles (clay and silt), and silt particles approximately accounted for 56.82%-71.99% of the total volume. The average volume fractions of fine particles were 78.86% and 65.77% for soil profile of Artemisia sacrorum grassland and woodland, respectively. The fractal dimensions of soil PSDs in five typical vegetation types ranged from 2.498-2.599, and most of them increased with the depth of soil layer. At the same soil layer, the fractal dimension of soil PSD showed the following order: Artemisia sacrorum grassland> Astragalus membranaceus grassland>farmland>shrubland>woodland, But there was no significant difference between shrubland and farmland. The fractal dimension of soil PSD in typical vegetation had extremely significant positive correlation with water content and the volume percentage of clay and silt (P<0.01), but significantly negative correlation with the volume percentage of sand and soil organic carbon content (P<0.05).