元江干热河谷典型林草地优先流区和基质流区土壤团聚体特征

Characteristics of Soil Aggregates in the Preferential Flow Area and Matrix Flow Area of Typical Forest-Grassland in Yuanjiang Dry-Hot Valley

[目的]明晰干热河谷区土壤优先流对红壤团聚体特征及其稳定性的影响,为该区植被恢复和水土流失防治提供理论依据。[方法]以元江干热河谷典型地段龙潭箐流域内的银合欢林地、扭黄茅荒草地为研究对象,基于染色示踪试验区分样地土壤优先流区和基质流区,利用干湿筛法结合分形理论分析两区内0-50 cm土层团聚体特征差异,并借助通径分析法表征各土壤理化因子对团聚体稳定性的影响。[结果]干湿筛后R0.25团聚体含量从大到小顺序为林地优先流区>林地基质流区>荒草地优先流区>荒草地基质流区,平均重量直径(MWD)和几何平均直径(GMD)与R0.25排序相同且呈现出随土层深度增加而减小的趋势,分形维数(D)与团聚体破坏率(PAD)则为相反规律并随土层加深D和PAD的值逐渐增大。对两区土壤团聚体稳定性影响较大的理化因子是土壤容重和黏粒含量,其决策系数分别为0.474和-0.644。[结论]荒草地土壤团聚体破坏率更高,土壤优先流区团聚体稳定性优于基质流区;土壤团聚体稳定性主要受黏粒含量、容重、有机质等因子影响。

[Objective]The influence of soil priority flow on the characteristics and stability of red soil aggregates in the dry and hot valley area was clarified to provide a theoretical basis for vegetation restoration and soil erosion prevention and control in this area.[Methods]Based on the dyeing tracing experiment,the soil preferential flow area and the matrix flow area were distinguished,and the characteristics of the aggregates of 0—50 cm soil layer in the two areas were analyzed by dry and wet sieving method combined with fractal theory,and the effects of the physical and chemical factors of each soil on the stability of the aggregates were characterized by the path analysis method.[Results]After dry and wet sieves,the R 0.25 aggregate contents decreased in the order:woodland priority flow area>woodland matrix flow area>barren grassland priority flow area>barren grassland matrix flow area,the change trends of average weight diameter(MWD)and geometric mean diameter(GMD)were the same as those of R 0.25,and showed a decreasing tendency with the increase of soil depth,and the fractal dimension(D)and the agglomeration failure rate(PAD)were the opposite patterns and gradually increased with the depth of the soil layer.The physicochemical factors impacting the stability of soil aggregates in the two regions were soil bulk density and clay content,and their decision coefficients were 0.474 and-0.644,respectively.[Conclusion]The soil aggregate failure rate is higher in barren grassland,and the stability of the aggregate in the soil priority flow area is better than that in the matrix flow area.The stability of soil aggregates is mainly affected by factors such as clay content,bulk density,and organic matter.