基于Le Bissonnais法对黄土高原森林植被带土壤团聚体及土壤可蚀性特征研究

土壤团聚体的组成和稳定性是衡量土壤结构和质量的主要指标,本研究应用Le Bissonnais(LB)法的3种筛分方法[快速湿润筛分法(FW)、慢速湿润筛分法(SW)、湿润振荡筛分法(WS)]模拟不同条件(暴雨、小雨、扰动)对土壤团聚体的破坏,通过测定预处理后的团聚体特征来表征黄土高原植被恢复对土壤团聚体的影响,以期为黄土高原植被恢复与生态建设提供科学依据。结果表明:在LB法的3种处理方法下,FW处理(暴雨)对土壤团聚体结构的破坏程度最大,处理后土壤团聚体主要以0.2 mm为主;SW处理(小雨)对土壤团聚体的破坏最小,WS处理(扰动)居中。土壤团聚体的平均重量直径(DMW),在0~10 cm和10~20 cm土层均表现为SWWSFW。土壤团聚体平均几何直径(DGM)0~10 cm和10~20 cm土层均表现为SWFWWS,土壤团聚体分形维数(D)0~10 cm和10~20 cm土层均表现为WSFWSW。在SW处理下,不同植被类型中铁杆蒿群落、黄刺玫群落(样点6、9)土壤团聚体DMW、DGM值较大,可蚀性(K)较小,表明这两个群落的土壤团聚体更为稳定,在小雨环境下更有利于水土保持。对WS处理,侧柏群落、三角槭群落(样点1、2、3)的土壤团聚体更为稳定,可蚀性(K)值较小,因此在外界扰动环境下,侧柏群落、三角槭群落的土壤抗侵蚀能力更强。在FW处理下,侧柏群落、三角槭群落(样点2、3)土壤团聚体DMW、DGM值较大,可蚀性(K)值较小,表明在外界大雨环境下,侧柏群落、三角槭群落的土壤团聚体稳定性更强,土壤抗侵蚀能力更强。总体来说,对于不同环境,不同植被类型下土壤的团聚体稳定性和抗侵蚀能力差异较大,因此应针对不同的环境,采取不同的植被恢复措施来提高土壤团聚体的稳定性。

Soil aggregate stability and erodibility under forest vegetation in the Loess Plateau using the Le Bissonnais method

The composition and stability of soil aggregates are the main indicators of soil structure and quality. For sustainable ecological restoration, soil aggregates stability under different vegetation types in the forest zones of the Loess Plateau was studied using the Le Bissonnais (LB) method. Three sieving methods of LB (SW: slow-wetting sieving method; FW: fast-wetting sieving method; WS: wet-stirring sieving method) were used to simulate light rain, heavy rain and disturbance. Soil samples were collected from 10 types of vegetation in Yanhe Catchment of Yan'an City. The mean weight diameter (D_MW), geometric mean diameter (D_GM), mass fractal dimension (D) of soil aggregates and soil erodibility (K) were calculated. The results showed that FW treatment was the most destructive to soil aggregate stability, under which soil water-stable aggregate particle size was mainly concentrated in the <0.2 mm size group. The SW treatment showed the least destructiveness to soil aggregate stability with soil water-stable aggregate particle size mainly concentrated in the >2 mm size group. It then explained that light rains had no strong damaging effects on soil aggregates. The orders of D_MW, D_GM, D and K were SW > WS > FW, SW > FW > WS, WS > FW > SW, and FW > WS > SW, respectively, in both 0-10 cm and 10-20 cm soil layers. Under SW, Artemisia gmelinii community and Rosa xanthina community had greater D_MW and D_GM, and smaller K, indicating the two vegetation types had advantages in soil protection under light rain. Under WS and FW, Platycladus orientalis community and Acer buergerianum communities had D_MW and D_GM, and smaller K. They were appreciate vegetation types for soil protection under heavy rain and strong disturbance. The results suggested that LB method was appropriately applicable in measuring soil aggregate structure in the Loess Plateau. The LB method not only simulated traditional wet sieving results, but also explained the mechanisms involved in the disintegration of soil aggregates under different conditions in terms of soil structure stability. The results also suggested that the vegetation types significantly influenced soil water-stable aggregates in the region. In summary, the stability of soil aggregates was improved by vegetation restoration in the forest zones of the Loess Plateau.