CONSERVATION EFFECTS ASSESSMENT FOR THE ST. JOSEPH RIVER WATERSHED
Location: National Soil Erosion Research Lab
Title: Fractal Features of Soil Particle Size Distribution Under Different Plant Communities in the Forested Region of Mountain Yimeng, China
Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 2009
Publication Date: October 30, 2009
Citation: Liu, X., Zhang, G., Heathman, G.C., Wang, Y., Huang, C. 2009. Fractal Features of Soil Particle Size Distribution Under Different Plant Communities in the Forested Region of Mountain Yimeng, China. Geoderma. 154:123-130.
Interpretive Summary: Fractal theory has been applied to various geological phenomena that display large, scale invariant and self-similar characteristics. In particular, fractal theory has been shown to be an appropriate means of modeling the process of fragmentation in both rocks and soils as a result of either natural processes or anthropogenic disturbances. Over the course of the past few decades, much of the Yimeng mountain forest in mid-eastern China has been destroyed due to economic growth and the exploitation of natural resources. Some plant communities have been transformed from protected forest areas to commercial forest (chestnut groves), cropland, or shrub-grassland areas for grazing. However, to date, no studies have been published investigating the soil fractal features associated with different plant communities in the Yimeng mountainous area. In this paper, we use the fractal scaling theory to analyze particle-size distribution (PSD), soil porosity and soil fractal dimension for seven different plant communities having similar soils and evaluate the relationships between selected soil properties and the fractal dimension of PSD. The objectives of this work were: 1) to assess the effect of converting native forests to different land uses on soil physical properties and, 2) to explore the possibility that the fractal dimension of soil particle-size distribution can be used as an integrating index for quantifying soil degradation due to anthropogenic disturbance.
In order to explore the effect of changes in plant communities and land use on soil properties, as a result of anthropogenic disturbances, we apply the theory of fractals and soil physics as a means to better quantify changes in particle-size distribution (PSD) and soil porosity. Fractal dimension analysis 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 relationship 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 (R2=0.83), and fine sand (R2=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 R2 values ranging from 0.74 to 0.91. 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.