富铁土团聚体稳定性的表征及其物理学机制

Characterization and physical mechanisms of aggregate stability in Ferrisols.

应用Yoder湿筛法、机械和化学分散法、LeBissonnaia法对富铁土的团聚体组成和稳定性进行了评价.3种方法测定的团聚体稳定性指标都与土壤黏粒含量呈极显著相关,湿筛法测定的>0.25mm团聚体含量和LeBissonnaia法测定的团聚体平均重量直径(MWD)与土壤有机质含量呈显著相关.土壤的团聚体稳定性以林地和高肥力园地最高,荒地和母质最低.LeBissonnaia法中富铁土团聚体经快速湿润(FW)、慢速湿润(SW)和预湿后扰动(WS)3种处理后,团聚体的MWD表现为WS>SW>FW,表明富铁土团聚体崩解的主要物理机制是团聚体中闭塞空气引起的消散.结果表明富铁土中的水稳性团聚体数量和稳定性是衡量土壤质量和抗蚀性的重要指标.

The aggregate size distribution (PSD) and aggregate stability in Ferrisols were measured by Yoder′s wet-sieving, mechanical shaking and chemical dispersion, and Le Bissonnais method. The aggregate stability indices as determined by the three methods were very significantly correlated with the clay content of Ferrisols. The amounts of aggregate with a diameter of >0.25 mm determined by wet-sieving and the mean weight diameter (MWD) determined by Le Bissonnais method were significantly correlated with organic matter content of Ferrisols. All the stability indices of aggregates of forest and orchard soils were higher than that of the other soils. The bare soil and soil-forming parent material had the lowest stability indices of aggregates. When ranked according to MWD in the three treatment of Le Bissonnais method, the order was WS>SW>FW. Fast wetting (FW) brought about the largest disruption while wet-stirring (WS) the least. This suggests that the basic mechanism of aggregate breakdown in Ferrisols lies in the shaking caused by the compression of air entrapped inside aggregates during wetting. The amounts and stability indices in Ferrisols can be taken as indicators for soil quality and soil antierodibilty.