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>Fractal Feature of Particle-Size Distribution in the Rhizospheres and Bulk Soils during Natural Recovery on the Loess Plateau China
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Fractal Feature of Particle-Size Distribution in the Rhizospheres and Bulk Soils during Natural Recovery on the Loess Plateau China
The application of fractal geometry to describe soil structure is an increasingly useful tool for better understanding the performance of soil systems. Only a few studies, however, have focused on the structure of rhizospheric zones, where energy flow and nutrient recycling most frequently occur. We used fractal dimensions to investigate the characteristics of particle-size distribution (PSD) in the rhizospheres and bulk soils of six croplands abandoned for 1, 5, 10, 15, 20, and 30 years on the Loess Plateau of China and evaluated the changes over successional time. The PSDs of the rhizospheres and the fractal dimensions between rhizosphere soil and bulk soils during the natural succession differed significantly due to the influence of plant roots. The rhizospheres had higher sand (0.05–1.00 mm) contents, lower silt (<0.002 mm) contents, and lower fractal dimensions than the bulk soils during the early and intermediate successional stages (1–15 years). The fractal dimensions of the rhizosphere soil and bulk soil ranged from 2.102 to 2.441 and from 2.214 to 2.459, respectively, during the 30-year restoration. Rhizospheric clay and silt contents and fractal dimension tended to be higher and sand content tended to be lower as abandonment age increased, but the bulk soils had the opposite trend. Linear regression analysis indicated that the fractal dimensions of both the rhizospheres and bulk soils were significantly linearly correlated with clay, sand, organic-carbon, and total-nitrogen contents, with R 2 ranging from 0.526 to 0.752 (P<0.001). In conclusion, PSD differed significantly between the rhizosphere soil and bulk soil. The fractal dimension was a sensitive and useful index for quantifying changes in the properties of the different soil zones. This study will greatly aid the application of the fractal method for describing soil structure and nutrient status and the understanding of the performance of rhizospheric zones during ecological restoration.
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机译：分形几何学在描述土壤结构方面的应用是一种越来越有用的工具，可以更好地了解土壤系统的性能。但是，只有很少的研究集中在根际区的结构上，在该区的能量流和养分循环最频繁发生。我们使用分形维数研究了黄土高原1、5、10、15、20和30年弃耕的6种农田的根际和块状土壤中的粒径分布（PSD）特征，并评估了变化在连续的时间内。由于植物根系的影响，自然演替过程中根际的PSD和根际土壤与大块土壤之间的分形维数差异很大。与早期和中期演替阶段（1-15年）中的块状土壤相比，根际土壤的含沙量较高（0.05-1.00 mm），粉土含量较低（<0.002 mm），分形维数较低。在30年的恢复过程中，根际土壤和整体土壤的分形维数分别为2.102至2.441和2.214至2.459。随着废弃年龄的增加，根际土壤和粉砂含量和分形维数趋于较高，而砂含量则趋于降低，但松散土壤却呈现相反的趋势。线性回归分析表明，根际和整体土壤的分形维数与粘土，沙子，有机碳和总氮含量呈线性关系，R 2 的范围为0.526至0.752（ P ＜0.001）。总之，根际土壤和块状土壤的PSD差异显着。分形维数是一个敏感而有用的指标，可用于量化不同土壤区域的特性变化。这项研究将大大有助于分形方法在描述土壤结构和养分状况以及对生态恢复过程中根际区性能的理解上的应用。
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