不同土地利用方式下第四纪古红土有机碳分布特征研究

以不同土地利用方式下（疏林荒草地、荒草地、林地和耕地）第四纪古红土和埋藏第四纪古红土剖面为研究对象，测定古红土各发生层全土及各粒级团聚体的有机碳含量，比较不同土地利用方式下第四纪古红土剖面及团聚体的有机碳分布特征。结果表明:（1）埋藏古红土有机碳含量较低，随深度分布均一，各粒级团聚体内有机碳含量随团聚体粒径减小而降低；（2）埋藏古红土出露地表后，由于受到人为活动影响，表层全土有机碳及各粒级团聚体有机碳含量均增加，呈现林地 > 耕地 > 疏林荒草地 > 荒草地 > 埋藏古红土的特征，其中，林地显著高于其他土地利用方式，说明林地是古红土分布区的一种较合理的土地利用方式；（3）耕地0 ~ 10 cm土层粒径 > 1 mm和 < 0.25 mm团聚体的有机碳含量均随团聚体粒径减小而逐渐增加，1 ~ 0.25 mm团聚体有机碳含量随团聚体粒径减小逐渐降低。其余土地利用方式下古红土均呈现 > 0.25 mm团聚体的有机碳含量随着团聚体粒径减小而逐渐降低，< 0.25 mm团聚体的有机碳含量随团聚体粒径减小而逐渐增加。

Characteristics of Soil Organic Carbon Distribution of Quaternary Red Soils under Different Land Use Patterns

The quaternary ancient Red soils under different land use patterns including woodland, sparse forest grassland, grassland, cultivated land, and ancient Red soils buried by loess were investigated. The soil organic carbon and aggregate associated organic carbon content of ancient Red soils were determined to address the soil organic carbon distribution with soil depth. The soil aggregate associated organic carbon content of ancient Red soils under different land use patterns were compared to the ancient Red soil buried by loess. The content of soil organic carbon in the ancient Red soil buried by loess was low and distributed uniformly with depth. The soil aggregate associated organic carbon content of the ancient Red soil buried by loess decreased with the decreasing of aggregate size. The ancient Red soils exposed to surface and influenced by different land use patterns had accumulated soil organic carbon in the surface horizon. The soil organic carbon content of ancient Red soils was the highest for woodland, followed by that of cultivated land and sparse forest grassland, and the lowest for the grassland. The soil organic carbon content of woodland was significantly higher than that of other land use patterns, indicating the woodland was an optimal land use pattern in the area of ancient Red soils. Except for the 0-10 cm depth in cultivated land, the organic carbon content of > 0.25 mm aggregates decreased gradually with the decreasing of aggregate size, and that of < 0.25 mm aggregates increased gradually with the decreasing of aggregate size. The soil organic carbon content of > 1 mm and < 0.25 mm aggregates increased gradually with the decreasing of aggregate size, and that of 1 - 0.25 mm aggregates decreased gradually with the decreasing of aggregate size in the 0 - 10 cm depth under cultivated land.