喀斯特森林植被自然恢复中土壤团聚体有机碳含量与团聚体分形特征

采用空间代替时间的方法,研究了茂兰喀斯特森林自然恢复中土壤团聚体有机碳含量与团聚体分形特征。结果表明:同一恢复阶段的同一土层中1 2 mm、0.5 1 mm团聚体质量百分比(4.74%52.37%)与其质量百分比有机碳贡献率(2.87%59.98%)均高于0.25 0.5 mm、<0.25 mm团聚体;相同土层中的相同粒级团聚体土壤有机碳含量(0 10 cm土层23.47 55.82 g·kg-1,>20 cm土层14.36 36.80 g·kg-1)与其质量百分比有机碳含量(0 10 cm土层1.34 22.12 g·kg-1,>20 cm土层0.57 11.93 g·kg-1)均随植被自然恢复呈增加趋势;同一恢复阶段的相同粒级团聚体土壤有机碳含量(0 10 cm土层23.47 55.82 g·kg-1,>20 cm土层14.36 36.80 g·kg-1)与其质量百分比有机碳含量(0 10 cm土层1.34 22.12 g·kg-1,>20 cm土层0.5711.93 g·kg-1)随土层加深呈减少趋势;同一恢复阶段的同一土层团聚体中1 2 mm团聚体中有机碳含量(16.9053.43 g·kg-1)最低但其质量百分比有机碳含量(5.24 22.12 g·kg-1)最高;随植被自然恢复土壤团聚体分形维数在0 10 cm土层(2.01 2.16)呈增加趋势、在>20 cm土层(2.04 2.24)呈减小趋势;喀斯特森林植被自然恢复中土壤结构演化的核心可能是上层土壤细化和下层土壤粗化;喀斯特森林植被自然恢复中土壤结构有所改善;土壤团聚体分形维数可以作为喀斯特植被自然恢复中土壤有机碳质量评价的指标;加强保护喀斯特森林使其自然恢复,既有利于土壤结构的改善与减少侵蚀,也有利于土壤有机碳循环和累积。

Studies on Organic Carbon Content and Fractal Features of Soil Aggregates with the Process of Natural Restoration of Karst Forest Vegetation

To study evolution of the characteristics of the soil aggregates organic carbon content and its fractal in the karst region of Maolan with the process of natural restoration of karst forest vegetation, the concept of space as a substitute for time was adopted. The results are as follows. The soil aggregate mass percentage(4.74% 52.37%) and its organic carbon contribution rate(2.87% 59.98%) in 1 2 mm and 0.5 1 mm soil aggregate were higher than that in 0.25 0.5 mm, <0.25 mm soil aggregate in the same soil layer at the same restoration stage. The organic carbon content and its mass percentage in soil aggregate in 0 10 cm layer (23.47 55.82 g·kg^-1, 1.34 22.12 g·kg^-1) were more than that >20 cm layer (14.36 36.80 g·kg^-1, 0.57 11.93 g·kg^-1) and increased with the process of the restoration and decreased with soil depth at the same restoration stage. The organic carbon content in 1 2 mm soil aggregate (16.90 53.43 g·kg^-1) was the lowest but the organic carbon content of 1 2 mm soil aggregate mass percentage (5.24 22.12 g·kg^-1) was the highest among all soil aggregates. The soil aggregate fractal dimension increased in the surface layer (0 10 cm layer, 2.01 2.16) but decreased in the low layer(>20 cm layer, 2.04 2.24) along with the process of the restoration. The evolution of soil structure may be that the surface layer soil aggregates turned thin but the low layer soil aggregates turned thicken along with the process of the restoration. The soil structure was improved along with the process of the restoration. The soil aggregate fractal dimension can be used as a comprehensively quantitative index to evaluate the soil organic carbon during the process of natural restoration; It is, therefore, essential to take strong measures to preserve karst forests and let them restore naturally, which can helps improve the soil structure, less soil erosion and accumulate organic carbon.