Fractal characteristics of soil particle under different vegetation cover restoration in Karst rocky desertification area
[Objective]This study investigates the distribution and fractal characteristics of soil particles in karstic rocky desertification areas,thus providing scientific basis for soil and water conservation and soil evaluation in rocky desertification areas.[Method]At the Karst Field Observation and Research Station of Guizhou Normal University,six vegetation covers including dragon fruit(Hylocereus undulatus),corn(Zea mays),walnut(Juglans regia),teak(Tectona grandis),and pepper(Zanthoxylum bungeanum)planting in valley and slope in the rocky desertification control area were chosen as the research objects.According to single and multifractal theory,fractal parameters of soil particles was investigated based on particle size distribution(PSD)measured in rainy and dry seasons.[Result]The results showed that(1)the PSD was concentrated in the range of 1.5-300 μm and the distribution was non-uniform.The particle was mainly silt with fine textureand low clay content;(2)Both vegetation cover and season had significant effects on the fractal dimension Dv(P＜0.05).The determination coefficient of R2 indicated that clay grains were most closely related to Dv.From wet season to dry season,the mean value of Dv decreased from 2.64 to 2.56.Meanwhile,erosion degree of soil fines significantly differed among these vegetation covers;(3)The multi-fractal characteristics showed that the PSD range of each plot was dominated by particles with a large volume fraction.The decreasing degree of the generalized dimensional spectrum Dq was higher at index q＜0 than at q＞0.The PSD were more sensitive to environmental changes in the sparse area;(4)The Dv value showed significant and positive correlations with clay and silt contents,while significant and negative correlation with sand content.However,the correlations of capacity dimension D0,information entropy dimension D1,D1/D0,and correlation dimension D2 with soil particles were contrary to those of Dv.The significant correlation of soil organic carbon/total nitrogen(SOC/TN)ratio was positive with silt particles while negative with sand particles,which indicates that the silt fraction played a dominant role in performing the carbon sequestration function.[Conclusion]Soil fractal dimension can be used as an indicator of the improvement effect of soil physical structure in karstic rocky desertification areas.The research results provides theoretical support for soil and water conservation and soil evaluation in rocky desertification areas.
fractal dimensionKarst rock desertificationparticle size distributionvegetation restoration
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