退化沙质草地开垦和围封过程中的土壤颗粒分形特征

研究了科尔沁退化沙质草地开垦和围封过程中土壤颗粒分形维数的变化特征，以及分形维数与土壤性状的关系.结果表明，不同开垦和围封年限的土壤颗粒分形维数(0～30cm)介于2.387～2.588之间.随着开垦年限的增加，0～15 cm层土壤颗粒分形维数从2.441降至2.387；围封11年后，0～15 cm层土壤颗粒分形维数增加到2.588.15～30 cm层土壤颗粒分形维数无明显变化.土壤颗粒分形维数是反映土壤质地的一个较好指标，重点反映粘粒含量，其次是粉粒含量.分形维数的变化能够很好地表征退化沙质草地土壤的化学、物理和生物学性状的变化趋势，可以作为评价退化沙质草地土壤性状的一个综合指标.

Distribution patterns and dynamics of dominant mountaintop elfin forest populations in Shimentai Nature Reserve in Guangdong

Based on the analysis of 42 soil samples from the grassland reclaimed and enclosed different years,this paper studied the fractal features of soil particle size distribution and the relationships between fractal features and soil properties.The results showed that the fractal dimension of soil particle size distribution in 0～30 cm soil layer ranged from 2.378 in reclaimed land to 2.588 in non-grazed enclosure,while that in 0～15 cm soil layer decreased from 2.441 in grazed grassland to 2.387 after 20 years of reclamation,and increased to 2.588 after 11 years of enclosure.No significant changes were found in fractal dimension in 15～30 cm soil layer between reclamation and enclosure.Statistic analysis indicated that the fractal dimension could objectively reflect soil texture,mainly the content of clay,and then silt content.There existed a remarkable quantitative correlation between fractal dimension and soil physical,chemical and biological properties,which meant that the fractal dimension could be used as a comprehensive and quantitative index in evaluating soil properties and grassland degradation degree.