滇东喀斯特山原红壤退化过程中土壤剖面团聚体和有机质变异

目的]揭示山原红壤的退化机理及效应,为滇东高原的石漠化效应研究及水土保持工作的开展提供科学依据。方法]以滇东山原红壤典型发育地带为研究对象,对山原红壤退化过程中灌丛、草地、松林、红裸土剖面的团聚体特征和有机质分布规律进行研究分析。结果]山原红壤退化过程中干筛法结果显示以大团聚体为主,并随着土层深度的增加而减少;湿筛法结果显示以微团聚体含量最高,灌丛、草地、松林在剖面上整体呈现出与干筛大团聚体一致的规律,红裸土呈现出:0—90cm层(B层)90—100cm层(C层)。土壤的稳定性和有机质含量在退化过程中基本呈现出:灌丛草地松林红裸土;随着土层深度的增加,灌丛、草地、松林土壤团聚体稳定性和物理性质逐渐劣化,有机质含量减少,红裸土则呈现出相反的规律;与A层、B层相比,较深层次的C层团聚体稳定性和有机质含量差异显著降低。结论]有机质与平均重量直径、几何平均直径、2mm粒级水稳性团聚体含量呈极显著正相关,与分形维数呈极显著负相关,增加有机质的含量应该是恢复和改良红裸土结构的重要手段。

Variations of Aggregates and Organic Matter in Soil Profile During Degradation Process of Mountainous Red Soil in Karst Area of East Yunnan Province

Objective] The mechanism and effects of red soil degradation were elucidated in order to provide scientific basis to soil and water conservation and rocky desertification effect of the east Yunnan Platean. Methods] This study examined the mountainous red soil based on the analysis of soil profile aggregates associated with different vegetation types, as well as the distribution of organic matter. Particularly, soil samples were taken from area covered with pine, shrubland, grassland or unvegetated red soils respectively in the karst area of east Yunnan Province. Results] The degraded soils were characterized by large aggregates after dry sieving, the contents of which generally decreased with depth. The highest content was micro-aggregates after wet sieving and samples from vegetation-covered area showed a similar trend as that with dry sieving, while the red bare soil showed the a trend of 0-90 cm (B layer) > 90-100 cm (C layer). Degree of stability and content of organic matter displayed a trend of shrub lands > pineland > grassland > red bare soil during the degradation process. Soil aggregate stability and physical properties of soils from shrubland, pineland and grassland gradually decreased and soil organic matter(SOM) deteriorated with increase of depth. On the contrary, all the proxies of red bare soil showed an opposite trend. In contrast to A and B layers, the structural property became inferior, and the content of SOM of C layer decreased significantly. Conclusion] There was a significant and positive correlation between the content of SOM and mean weight diameter, geometric mean diameter and >2 mm size aggregate content, but a significant negative correlation between SOM and fractal dimension. All these suggest the possible and viable way to improve the structural condition of red bare soil by increasing the content of SOM.