沙漠化逆转过程中土壤颗粒分形维数的变化特征——以宁夏盐池县为例

通过野外采样和实验室分析,利用空间变化代替时间变化的手段,研究了宁夏盐池县多年围封区沙漠化逆转过程中土壤颗粒分形维数的变化特征。结果表明:沙漠化逆转的过程是土壤颗粒向细粒化方向演变及养分富集的过程。分形维数与土壤养分和黏粉粒等细颗粒的变化趋势相同,随着沙漠化程度的减小,分形维数呈逐渐增大的趋势。它与土壤粒径分布、有机质、全氮、全磷、速效氮、速效磷、速效钾之间存在着高度的线性相关,对黏粒含量的变化最为敏感。因此,可用土壤颗粒分形维数的变化来反映该区土壤理化性状的变化特征,并将其作为衡量沙漠化逆转过程中土壤结构、肥力状况及土壤退化恢复程度的一个综合性定量指标。

Changes in Fractal Dimension of Soil Particle During Reversal of Desertification——A case study in Yanchi County,Ningxia Hui Autonomous Region

Based on field investigation and laboratory analysis,by the method of time-space mutual substitution,soil particle distribution and the content of organic matter,total N,total P,available N,available P and available K was examined; and fractal dimension of soil particle was counted by using the method of Peiling Yang,the changes of soil particle fractal dimension was examined at a site exhibiting the reversal of desertification in enclosed area for many years of Yanchi County. Then adopting statistic analytical methods,the relationship between soil particle fractal dimension and soil physical-chemical properties were discussed. The results show that the content of coarse sand,medium sand and fine sand decreased,very fine sand and silt + clay increased during reversal of desertification. The reversal of desertification is the process of the fineness of the soil texture,and accelerates the accumulation of soil nutrients,along with the decrease of the degree of soil desertification and the increase of the coverage of the vegetation. As a result of this,soil organic matter,total N,total P,available N,available P,available K all showed the tendency of constant increase. The fractal dimension of soil particle size distribution increased as the decreasing of the desertification degree,and had the similar change trend to that of soil nutrients index and silt + clay. Results of correlation analysis reveals that there were remarkable quantity relationships between fractal dimension and soil properties. The content of sand exhibited a significant negative correlation with fractal dimension,however the contents of silt,clay,soil nutrients showed significant positive correlation with fractal dimension. From above,it can be concluded that the changes of soil particle fractal dimension could reflect the changes of soil physico-chemical properties,and it could be used as a comprehensively quantitative index to evaluate the soil structure,fertility states,and the recovered degree of soil degradation during reversal of desertification.