干旱区生态环境知识资源中心

Fractal dimension analyses of PSD and soil porosity were determined for the 0-20 cm soil layer representing different plant communities and land management in the Yimeng mountainous region of mid-eastern China. The soil types in this area are typically comprised of coarse sand and gravel. The results show that, compared with the protected forest preserve areas, soil physical properties in commercial Chinese chestnut groves (CM), cropland (ZM) and mixed shrub-grass lands (SH) were more sensitive to soil degradation under their respective long-term management strategies. In general, amounts of silt and clay decreased under CM, ZM, and SH land practices, while fine sand content increased, resulting in lower values for soil total porosity and capillary porosity. For protected forest, soil physical properties were enhanced due to litter decomposition and plant root development under long-term preservation measures. Considering the different plant communities, the overall fractal dimensions of PSD ranged from 2.141 to 2.526, with the fractal dimensions of ZM, SH and CM being far lower (2.141 to 2.166) than the mean value (2.395) of the protected forest land. The relationships between fractal dimension and PSD and soil porosity were also examined. There were significant correlations found between fractal dimension and the amount of silt and clay (R-2 = 0.83), and fine sand (R-2 = 0.64), with increasing fractal dimension values corresponding to higher silt and clay contents and lower sand content. There also existed strong linear relationships between fractal dimension and soil porosity with R-2 values ranging from 0.74 to 0.91. Correlations of D-m with capillary porosity, in association with the type of plant community, provided strong evidence that vegetation management affects small scale aggregation which influences the water-holding capacity of the soil, thus implying that Dm may be considered a good measure for quantifying aggregation and the effects of vegetation management on soil quality or soil degradation. This study demonstrates that fractal dimension analysis may be used to better quantify differences in PSD and soil porosity associated with soil degradation caused by anthropogenic disturbance of plant community environments. (C) 2009 Elsevier B.V. All rights reserved.