重庆城郊紫色土小流域草地入渗特征

Infiltration characteristics of grassland in small watershed of purple soil in suburban Chongqing

为揭示植物根系对紫色土小流域草地渗透性能的影响,本研究选取重庆城郊紫色土小流域4种常见草本植物(窃衣、黄鹌菜、黑麦草和蒲儿根)的根土复合体为研究对象,以无根土为对照,采用单株植物根系进行一维入渗实验,探讨植物根系结构特征与根土复合体渗透性能的关系,并采用入渗模型进行模拟。结果表明:根土复合体和无根土入渗均呈现先陡降后趋于稳定的趋势;与无根土相比,根土复合体稳定入渗率可提高1.35~2.96倍,且须根系根土复合体入渗率均高于直根系,其中蒲儿根提高土壤入渗性能更好;根长密度、根表面积密度、根体积分形维数与根土复合体的初始入渗率、稳定入渗率、平均入渗率、累积入渗量均呈极显著正相关(P<0.01),而根体积密度与土壤初始入渗率、根重密度与稳定入渗率相关性不显著(P>0.05);Mezencev模型最适合表征4种草本植物根土复合体和无根土入渗(R^(2)均为0.99),其后依次是Kostiakov模型、Horton模型和Philip模型;直根系根土复合体对Kostiakov、Philip和Horton等3种模型的适用性优于须根系根土复合体。研究结果可从植物根系角度为紫色土区防治水土流失提供理论依据。

To understand the effects of root system on the infiltration capacity of grasslands in a purple soil water-shed,we conducted a one-dimensional infiltration experiment with four common herbaceous plants(Torilis scabra,Youngia japonica,Lolium multiflorum,and Sinosenecio oldhamianus)in suburb Chongqing.The relationship be-tween the characteristics of plant root structure and the infiltration capacity of root-soil complex was examined,and the Kostiakov,Mezencev,Horton,and Phillip infiltration models were used to simulate the infiltration process.The results showed that the infiltration processes of root-soil complex and rootless soil decreased sharply at first and then decreased slowly until stable.The stable infiltration rate of root-soil complex increased by 1.35-2.96 times com-pared with that of rootless soil.The infiltration rate of fibrous root-soil complex was higher than that of taproot-soil complex.Sinosenecio oldhamianus performed better in improving the infiltration performance of purple soil.Root length density,root surface area density,and root volume fractal dimension were significantly positively correlated with the initial,stable,average,and cumulative infiltration rates of the root-soil complex(P<0.01).However,there was no significant correlation(P>0.05)between root volume density and soil initial infiltration rate,root weight density and stable infiltration rate.The Mezencev model was the most suitable to characterize the infiltration of root-soil complex of the four herbaceous species and rootless soil(R^(2)=0.99),followed by Kostiakov model,Horton model,and Philip model.Moreover,the Kostiakov,Philip,and Horton models performed better in simulating the infiltration of taproot-soil complex than that of fibrous root-soil complex.The results can provide a scientific basis for slope vegetation construction and soil erosion prevention in purple soil areas.