青藏高原不同草地利用方式对土壤粒径分形特征的影响

研究青藏高原草地土壤粒径结构分形特征，为该地区土壤质量评价和生态恢复提供科学依据。以青藏高原4种高寒草地(放牧、围栏禁牧、围栏禁牧+补植、未干扰)为对象，采用分形理论，研究不同利用方式对高寒草地土壤颗粒组成及分形特征的影响，明确土壤粒径分形特征的影响因素。结果表明：与放牧和围栏禁牧+补植相比，围栏禁牧草地中黏粒和粉粒体积分数分别增加了60%—91.1%、43.5%—80.1%,禁牧能够促进土壤砂粒向黏粒和粉粒转变。不同草地利用方式对分形维数有显著影响，单重分形维数D值依次为放牧草地<围栏禁牧+补植草地<未干扰草地=围栏禁牧草地，多重分形维数，包括信息维数D₁、信息维数/容量维数比值D₁/D₀和关联维数D₂依次为放牧草地<围栏禁牧+补植草地<围栏禁牧草地<未干扰草地。单重分形维数D与土壤黏粒、粉粒呈极显著正相关(P<0.01);砂粒、黏粒、粉粒、有机碳和全氮是多重分形维数的限制因素。信息维数D₁、信息维数/容量维数比值D₁...

Effects of different meadow use types on the fractal characteristics of soil particle in the Qinghai-Tibet Plateau

This study investigated the effect of different meadow use on the fractal characteristics of soil particle to provide the scientific basis for soil quality evaluation and ecological restoration of alpine grassland in the Tibetan Plateau. The soil particle composition and fractal characteristics were examined by the fractal theory in four alpine meadows (grazed meadow, fenced meadow, fenced+reseeded meadow, and undisturbed meadow) in the Tibetan Plateau, and their driving forces were clarified. The results showed that the volume fraction of clay and silt particles in fenced grazing grassland increased by 60%-91.1% and 43.5%-80.1%, respectively, compared with those in grazed meadow and fenced+reseeded meadow; grazing prohibition promotes the transformation of soil sand to clay and silt. Changes in meadow use type had significant effects on the soil fractal dimension. Single fractal dimension (D-value) was in the order of grazed meadowD₁), entropy dimension/capacity dimension (D₁/D₀) and correlation dimension (D₂), were in the order of grazed meadow < fenced+reseeded meadow < fenced meadow < undisturbed meadow. D-value of the single fractal dimension was positively correlated with the contents of clay and silt (P<0.01); the contents of sand, clay, silt, organic carbon and total nitrogen are the dominant factors affecting the multifractal parameters. D₁, D₁/D₀ and D₂ were positively correlated with the contents of soil organic carbon, total nitrogen, total phosphorus and nitrate nitrogen. In conclusion, multifractal dimension parameters can be used as indicators to evaluate the characteristics of soil fertility, and grazing prohibition can improve the soil texture in Tibetan Plateau.