汾河流域下游不同土地利用方式下优先流区与基质流区土壤团聚体稳定性分析

优先流是水分和溶质在土壤中非均质性运移的普遍现象,但对其形成的优先流区和基质流区土壤团聚体稳定性的研究还较少。为了阐明土壤团聚体破碎机制的差异,研究以汾河流域下游农田、撂荒地和果园3种土地利用方式为对象,采用野外染色示踪法与Le Bissonnais(LB)法分析了土壤染色区分下优先流区与基质流区土壤团聚体稳定性特征。结果表明:土壤染色率主要分布在0—30 cm土层,在10—30 cm土层果园显著高于撂荒地。LB处理的>0.25 mm团聚体含量和平均重量直径(MWD)在不同土地利用方式下表现为果园>农田>撂荒地,相对消散指数(RSI)和相对机械破碎指数(RMI)则有相反的趋势。优先流区在10—20 cm土层比基质流区具有更强的团聚体稳定性以及抵抗消散作用和机械破坏能力。土壤染色率与快速湿润的MWD呈显著负相关,与RSI呈显著正相关。研究表明果园比农田和撂荒地具有更好的优先流特征和团聚体稳定性,并且优先流区抗团聚破碎能力比基质流区更强,这将有利于维持优先流途径稳定性。

Analysis on Soil Aggregate Stability of Preferential Flow and Matrix Flow Domains Under Different Land Use Types in the Lower Reaches of Fen River Watershed

Preferential flow is a common heterogeneous phenomenon of movement of water and solute in soil. However, the difference of soil aggregate stability between preferential flow domain and matrix flow domain are still unclear. In order to clarify the difference of soil aggregate fragmentation mechanism, soil dyeing percentage and aggregate stability in preferential flow and matrix flow domain were analyzed by using dye tracer in field and Le Bissonnais(LB)method in this study. The results showed that soil dyeing percentage mainly distributed in 0—30 cm soil depth, and orchard had a significantly higher values than abandoned land in 10—30 cm depth; the macro-aggregate(>0.25 mm)content and mean weight diameter(MWD)with LB treatments had similar change trends in the order: orchard>farmland>abandoned land, while the relative slaking index(RSI)and relative mechanical breakdown index(RMI)had the opposite tendency; in 10—20 cm soil depth, the preferential flow domain had stronger aggregate stability and resistance to slaking and mechanical breakdown than the matrix flow domain; soil dyeing percentage was negatively correlated with MWD and positively correlated with RSI. These results suggest that orchard had better preferential flow characteristics and aggregate stability than farmland and abandoned land, and the resistance to aggregates slaking and mechanical breakdown of preferential flow domain was stronger than that of matrix flow domain, which was beneficial for maintaining the stability of preferential flow path.