红裸土是古气候影响下残存于高原面的古红土。对14个典型样地表层样品的团聚体稳定性及其影响因素进行了研究和分析，结果表明：根据国际制的划分，红裸土总体属于粉质黏土；＞0.25 mm水稳性团聚体含量(WR_0.25) 在28.77% ~ 52.87%，团聚体结构破坏率(PAD)在34.28% ~ 68.10%，平均重量直径(MWD)在0.53 ~ 1 mm，几何平均直径(GMD)在0.37 ~ 0.58 mm，分形维数(FD)在2.79 ~ 2.92，与其他西南典型岩溶区土壤相比，5个指标均反映出红裸土结构稳定性差，抗蚀性弱，物理性质劣的特征。分析还表明，红裸土团聚体的水稳性结构指标均与有机质含量呈现出显著或者极显著的相关关系，与黏粒含量均呈现相关关系，但不显著。红裸土缺乏有机质的供给，长期裸露，导致表层土壤结构稳定性劣化，是造成红裸土发育区水土流失严重和难以生长植被的重要原因。

Red bare soil is a kind of the paleosol remained in the plateau surface influenced by the ancient climate. The study analyzed the stability and influential factors of the surface-layer soil aggregates in 14 typical samples of paleosol. The results showed that: 1) on the basis of international standard partition, the red bare soil generally belonged to silty clay in texture; 2) the indices of WR_0.25 ranged from 28.77% to 52.87%, PAD from 34.28% to 68.10%, MWD from 0.51 to 1 mm, GMD 0.37 to 0.58 mm, and FD from 2.79 to 2.92, respectively, all the above parameters reflected red bare soil are poor in structural stability, anti-erodibility and physical property when compared with other typical soils in southwest karst area of China; 3) soil orgnic matter played a more important role in deciding water stability of read bare soil aggregates than clays. Long-term bareness and soil orgnic matter shortage deteriorate soil structure stability, led to severe soil erosion and hinder vegetation restoration in red bare soil area.

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国家自然科学基金项目(41061021)和云南省科技计划项目(2012CA024)资助