3种草本植物根系对土壤抗蚀特性的响应

Root system responses of three herbs to soil anti-erodibility

为探明南方红壤区常见草本植物根系与土壤抗侵蚀性能之间的关系,以湖北省两种代表性土壤(黄棕壤和红壤)内生长的3种草本植物香根草(Vetiveria zizanioides)、白三叶(Trifolium repens)和黑麦草(Lolium perenne)为研究对象,在两种土壤中分别采集3种草本植物根土复合体(共6种根土复合体处理),并设裸地对照,采用集中水流冲刷试验,测定了土壤细沟可蚀性和根系参数,系统分析了该地区常见水土保持草本植物根系抗侵蚀特征。结果表明,根系存在可有效增强土壤抗侵蚀性能,不同植物的增强效果存在差异,增强效果表现为香根草>白三叶>黑麦草;根长密度(RLD, root length density)是影响土壤可蚀性的最重要根系参数,RLD可较好地模拟两种土壤的根土复合体分离能力变化(R2≥0.930),而根重密度(RMD, root mass density)和根面积比(RAR, root area ratio)也有重要作用;直径小于1.0 mm根系是影响根土复合体抗侵蚀性能的重要指标,其中根径为0.5～1.0 mm的细根作用更为显著(P <0.01)。研究结果表明,香根草是南方红壤区一种重要的水土保持植物种类,可为区域内植被恢复中草本植物的选取以及根系特征与土壤抗蚀特性的关系研究提供理论依据。

To explore the relationship between herb roots and anti-erodibility in the red soil region of southern China, we examined three herbs (Vetiveria zizanioides, Trifolium repens and Lolium perenne) that naturally grow in two types of soil (yellow-brown and red) in Hubei Province. The soil-root composite of the three herbs were collected from two types of soil, with a total of six soil-root composite treatments. Each treatment (including the control) was subjected to concentrated flow scouring (hydraulic flume: 4.00 m long, 0.20 m wide) under three different water-flow shear stresses ranging from 2.41 to 15.03 Pa. Soil rill erodibility and root parameters were measured to investigate the effects of different soil erodibility characteristics. Results show that roots strengthen soil erodibility significantly. However, the influence of roots varied for different herbs, with Vetiveria zizanioides and Lolium perenne showing the largest and smallest enhancement effects, respectively. Root length density (RLD) was the root parameter that had the largest effect on soil erodibility, as RLD provided the most accurate simulation (R2 ≥ 0.930) of the soil detachment capacity change of two soil-root composites. Root mass density (RMD) and root area ratio (RAR) also had large effects on soil erodibility. Root diameters of less than 1.0 mm increased soil-root composite anti-erodibility, with the most significant effects observed for root diameters of 0.5~1.0 mm (P < 0.01). Overall, we found that Vetiveria zizanioides is an important plant species that can improve soil and water conservation in the red soil region of southern China. Results from this study provide an herb selection reference for regional restoration projects and describe the relationship between root features and soil anti-erodibility.