| In order to quantitative describe the soil structure and quality under the representative plant communities of typical small watersheds in Huaihe River Areas, including jiangzihe ,yinghe and jiuxianshan watersheds, the distribution of soil particles are analysed on monofractal and multifractal theories. For exploring the heterogeneity of the soil structure ,quality and relationships between fractal parameters and soil physicochemical properties, the fractal parameters for the distribution of soil particles are calculated, and the soil particle size distribution,organic matter, pH ,total N,available N,total P, available P and available K are measured. The aims to discuss the heterogeneity of soil structure and quality under different land uses are to offer scientific theoretic and technique bases for dispositon to plant communities and choosing standtypes of small watersheds. The main research conclusions are as follows:(1) The fractal characteristics on soil particles are significantly different under different types of land uses.The mono-fractal dimensions and multi-fractal parameters for soil particle size distributions such asΔα, R, f[α(-1)]-f[α(0)], f[α(1)]/f[α(0)], D0, D1, D2 and D1/D0, are following the order as protective forest land(shrubbery extra), economic forest land and farmland. Results of multifractal analysises show that: D(q)'s andα(q)'s variability of protective forest land are most obvious on whole q interval, the curves of f(α)~αshow protuberant functions,and the multifraction structure and dissymmetry degree are obvious than others. This means that the affect of protective forest lands on the heterogeneity of soil particle size distribution is the biggest.The mono-fractal dimensions D and multi-fractal parameters for soil particle size distributions such asΔα, R, f[α(-1)]-f[α(0)], f[α(1)]/f[α(0)], D0, D1, D2 and D1/D0, are following the order as the mixed forest(Pinus massoniana & Quercus variabilis)/spinney,tea plantation(Camellia sinensis),bamboo forest(Phyllostachys pubescens)/paddy field in jiangzihe watershed, the D(q)'s andα(q)'s variability of the mixed forest(Pinus massoniana & Quercus variabilis)/spinney are most obvious on whole q interval, the curves of f(α)~αshow protuberant functions,and the multifraction structure and dissymmetry degree are obvious than others.The mono-fractal dimensions D and multi-fractal parameters for soil particle size distributions such asΔα, R, f[α(-1)]-f[α(0)], f[α(1)]/f[α(0)], D0, D1, D2 and D1/D0, are following the order as the forest land,wasted land/shrubbery and terraced fields in yinghe watershed, the D(q)'s andα(q)'s variability of the forest(Quercus acutissima)/spinney are most obvious on whole q interval, the curves of f(α)~αshow protuberant functions,and the multifraction structure and dissymmetry degree are obvious than others.The mono-fractal dimensions D and multi-fractal parameters for soil particle size distributions such asΔα, R, f[α(-1)]-f[α(0)], f[α(1)]/f[α(0)], D0, D1, D2 and D1/D0, are following the order as protective forest land, economic forest land/farmland in jiuxianshan watershed, the D(q)'s andα(q)'s variability of the forest(Populus tomentoa, Quercus acutissima,Platycladus orientalis,and Robinia pseudoacacia) are most obvious on whole q interval, the curves of f(α)~αshow protuberant functions,and the multifraction structure and dissymmetry degree are obvious than others.(2) The volume fractal dimention D and multi-fractal parameters such asΔα, R, f[α(-1)]-f[α(0)] , f[α(1)]/f[α(0)], D0, D1, D2 and D1/D0, are significantly positively correlated with the content of clay soil particles, the finer of soil texture means the more heterogeneous of the soil paticle distribution and the greater singularities. The protective forest lands can increase soil fractal dimensions,the heterogeneity of soil texture and soil structure by raising the content of clay soil particles.The affect of different types of land uses on the soil physicochemical characteristics is significantly different. The soil physicochemical characteristics are also different in the same plant communities of different areas.The content of clay soil particles of protective forest lands is higher than economic forest land and farmland, and the improving effect of protective forest lands on soil is more stronger than others. The soil organic matter content under different types of land uses show the unified law, that is protective forest lands'are higher than others,and other chemical indexes are not the same. The soil physicochemical characteristics are also different in the same plant communities of different areas. The content of clay and silt soil particles and soil organic matter of protective forest lands are higher than economic forest land, this is due to the effect of natural factors such as parent material, climate, temperature and etc, and the productive and management measures of artifical activities such as pruning,cutting, fertilizing and etc. The effect on soil physicochemical characteristics of artifical activities is the biggest among these factors.(3) Correlations analysises between soil fractal parameters and soil physicochemical characteristics show that: The soil orgnic matter as the one indicator of soil quality is significantly positively correlated with the volume fractal dimention D and multi-fractal parameters such asΔα, f[α(-1)]-f[α(0)], f[α(1)]/f[α(0)], D0, D1, and D1/D0, and also significantly positively correlated with the content of clay and silt soil particles, and significantly negatively correlated with the content of sand particles. It meas that: the more of fine-grained materials of clay and silt soil particles means the more retention of orgnic matter on soil, the more ability of increasing the soil fertility,and accordingly increasing the soil volume fractal dimension and multi-fractal parameters. The conclusion is: the monofractal and multifractal parameters can be better as the potential indicators to reflect the soil structure and the soil quality. |
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