石漠化地区土地利用方式对土壤团聚体稳定性及有机碳的影响

以典型高原山地喀斯特石漠化6种土地利用方式土壤为研究对象，探讨不同生态恢复条件下，坡耕地转变为林地、草地及林草套种地后对表层土壤结构稳定性及其有机碳含量的影响。结果表明:在坡耕地实施石漠化治理措施，造林种草后，>0.25 mm团聚体含量显著增加，以人工林、次生林居多，坡耕地较少。在干湿筛处理下，采用平均质量直径（MWD）、几何平均直径（GMD）、分形维数（D）、>0.25 mm团聚体含量等指标来表征的团聚体稳定性显示，人工林和次生林土壤团聚体稳定性较强，坡耕地和林草套种地土壤团聚体稳定性较弱。总体上不同土地利用方式均以小粒级团聚体有机碳含量最高，>5 mm和2~5 mm水稳性团聚体有机碳对土壤有机碳的贡献率最大（除农耕地）；土壤大团聚体对土壤有机碳的固定起主要作用。石漠化坡耕地退耕还林种草有利于促进土壤表层土壤结构的稳定及有机碳的积累。 

Effects of land-use patterns on soil aggregate stability and organic carbon in rocky desertification areas

The Salaxi town of Bijie City, Guizhou Province is a representative karst mountainous demonstration district, where the karst accounts for 74.25% of the entire area. The exposed rocks are dominated by limestone, limestone and sand shale, with widespread potential and mild rocky desertification. This region hosts zonal yellow soil, dominated by arable and forest land, with a small amount of grassland. These lands are used in six types， secondary forest, artificial forest, natural shrub grassland, artificial grassland, forest and grass interplanting land and sloping farmland, which have largely same slope angle, slop facing direction and elevation. By monitoring the number of soil aggregate, soil aggregate stability, soil aggregate organic carbon and other indices, this work analyzes the influence of the conversion of slope farmland into forest land, grassland and forest-grass interplanting land on the stability of surface soil structure and the content of organic carbon under different land use patterns, and reveals the stability of soil structure and carbon sequestration capacity after implementing rocky desertification control measures in this area, providing a scientific basis for the prevention and control of soil erosion and the improvement of soil erosion resistance in rocky desertification areas. The results show that， (1) the aggregate content of >0.25 mm increased significantly after the implementation of forestation and planting, with more plantation and secondary forests and less sloping farmland.(2) After the dry and wet sieve treatment, the stability of aggregates and erosion resistance characterized by GMD, MWD and D indexes and >0.25 mm aggregate content show that the soil aggregate stability of plantation and secondary forests was strong, whereas the soil aggregate stability of sloping farmland and forest-grass interplanting land was weak . (3) In general, the content of soil organic carbon of small-grained aggregate is the highest for different land use patterns, and the contribution rate of water stable aggregate organic carbon of >5 mm and 2-5 mm to soil organic carbon is the largest (except for sloping farmland). Large soil aggregates play a major role in the sequestration of soil organic carbon. After the transformation of sloping farmland into forest and grass land in rocky desertification areas, the number of large soil aggregates (>0.25 mm) increases, the stability of soil aggregates is enhanced, and the organic carbon content of soil aggregates does not exhibit significant increase. On the whole, returning farmland to forest and planting grass in rocky desertification sloping land is beneficial to the promotion of the stability of soil surface soil structure and the accumulation of organic carbon.