西南岩溶区土地利用变化对团聚体稳定性及其有机碳的影响

土壤团聚体稳定性与团聚体有机碳的关系及其对土地利用变化的响应研究,对西南岩溶区估算土壤碳汇潜力、改善石漠化问题和土地利用管理有重要意义.为探究西南岩溶区土地利用方式变化对土壤团聚体组分、稳定性及团聚体有机碳含量的影响,选取次生林、柚子林、水田、花椒林和旱地这5种典型土地利用方式下0~30 cm的土壤为研究对象,分析了不同土地利用方式下土壤团聚体组分及其有机碳含量的变化规律,揭示了土壤团聚体组分与团聚体有机碳含量之间的关系,探讨了土地利用方式变化后土壤团聚体对有机碳含量变化的贡献.结果表明,次生林、柚子林和水田表层（0~15 cm）土壤中大团聚体的含量分别为63.32%、52.38%和47.77%,显著高于旱地（23.70%）,下层（15~30 cm）土壤趋势相同；次生林、柚子林和水田土壤团聚体的几何平均直径（GMD）和平均质量直径（MWD）显著高于旱地.表层土壤中,次生林和水田的有机碳含量显著高于其他土地利用方式,下层土壤中,只有水田的有机碳含量显著高于其他.各土地利用方式下,团聚体有机碳含量均表现为：大团聚体>微团聚体>粉黏粒.大团聚体对土壤有机碳含量的增加具有积极作用,而粉黏粒组分则有消极作用.相关性分析表明,土壤大团聚体含量与GMD、MWD及土壤团聚体有机碳含量均呈显著正相关.土壤大团聚体含量的增加有利于提高土壤团聚体的稳定性和储存土壤有机碳,适度发展林业和水田耕作有利于提高西南岩溶区土壤的固碳潜力.

Effects of Land Use Change on Soil Aggregate Stability and Soil Aggregate Organic Carbon in Karst Area of Southwest China

Investigating the relationship of soil aggregate stability with the organic carbon in the aggregate and its response to land use change is conducive to the estimation of soil carbon sink potential, improvement of rocky desertification, and rational land use in karst areas of Southwest China. In order to explore the effects of land use change on the composition and stability of soil aggregate stability as well as the content of aggregate organic carbon, the soil (0-30 cm) of five land use types (secondary forest, pomelo forest, paddy field, pepper forest, and dry land) was selected as the research object. The characteristics and correlation of soil aggregate components and organic carbon under different land use patterns were obtained, and the contribution of soil aggregates to the change in organic carbon after land use change was calculated. The results showed that the macroaggregates in the surface soil (0-15 cm) of the secondary forest, pomelo forest, and paddy field were 63.32%, 52.38%, and 47.77%, respectively, which were significantly higher than that of dry land (23.70%), as was also seen in the lower layer (15-30 cm). The geometric mean diameter (GMD) and mean weight diameter (MWD) of soil aggregates in the secondary forest, pomelo forest, and paddy field were significantly higher than those in dry land. In the surface soil, the organic carbon of the secondary forest and paddy field was significantly higher than that of other land use patterns. By contrast, in the lower soil layer, only the organic carbon of the paddy field was significantly higher than that of the others. Under different land use patterns, the organic carbon content of aggregates followed the same order of macroaggregates > microaggregates > silt and clay, indicating that macroaggregates allowed soil organic carbon to accumulate, whereas silt and clay did the opposite. According to correlation analysis, the content of soil macroaggregates was significantly positively correlated with GMD, MWD, and soil aggregate organic carbon, suggesting that the increase in soil macroaggregates could improve the stability of soil aggregates and store more soil organic carbon. Further, as land use change may have significantly affected the soil aggregate, moderate development of forestry and paddy cultivation is suggested to improve the soil carbon sequestration potential in the karst area of Southwest China.