三峡库区几种耐水淹植物根系特征与土壤抗水蚀增强效应

ROOT FEATURES OF SEVERAL FLOODING-TOLERANT PLANTS AND THEIR ROLES IN ENHANCING ANTI-ERODIBILITY OF THE SOIL IN THREE GORGES RESERVOIR REGION

为明确用于三峡库区消落区植被构建的岸生植物物种根系特征与土壤抗水蚀之间的关系,对狗牙根(Cynodon dactylon(L)Pers.)、空心莲子草(Alternanthera philoxeroides(Mart)Griseb)、荻(Triarrhena saccharifloraNakai)、牛鞭草(Hemarthria compressa(L.f.)R.Br.)、香附子(Cyperus rotundusL.)、野古草(Arundinella anomala Steud.)等6种耐水淹植物根系进行了研究。利用根钻(Eijkelkamp agrisearch equipmentmodel 15.01)在野外直接取样的方法,获取了含有目标物种根系的土柱试验样品,采用改进的抗崩解装置测量土壤的水蚀速率,计算了这6种植物根系对土壤的抗水蚀增强系数,并使用根系分析系统(WinRHIZO Pro.2004c)对根系特征进行了分析。研究发现,空心莲子草、荻、香附子和狗牙根的根冠比均值较大,野古草、荻具有较大的根长密度和根表面积密度;含有根系的土壤水蚀速率显著低于对照,空心莲子草、荻、野古草的土壤抗水蚀增强系数显著高于其他3个物种;根长密度、根表面积密度均与土壤抗水蚀增强系数之间呈极显著的线性关系;根系径级中D≤2 mm的根系与土壤抗水蚀关系最为密切,土壤抗水蚀增强系数与D≤2 mm根系的根长密度和根表积密度均呈显著的线性关系,相关系数随着径级的增加而减小。结果表明,6物种均能显著增强土壤的抗水蚀能力,空心莲子草、荻、野古草的增强作用最为明显;根长密度、根表面积密度能很好地表征土壤的抗水蚀能力,尤其是D≤2 mm或D≤0.5 mm根系的根长密度和根表积密度,可以作为表征土壤抗水蚀能力的最重要参数。

To investigate characteristics of the root systems of the plants comprising the vegetation in the waterlevel-fluctuation-zone of the Three Gorges Reservoir Region and their influence on the anti-erodibility of soil, 6 flooding-tolerant plants, i.e. Cynodon dactylon （ L ） Pers. , Alternanthera philoxeroides （Mart） Griseb, Triarrhena sacchariflora Nakai, Hemarthria compressa （ L. f. ） R. Br. , Cyperus rotundus L. , and Arundinella anomala Steud, were selected and investigated in the experiment. Root-soil core samplers （Eijkelkamp agrisearch equipment model 15.01 ） were used to take samples from the fields for analysis, a modified hydraulic flume device was applied to analyze the soil samples for water erosion rate and thereafter obtain anti-erodibility enhancement coefficients of root systems of the 6 plants. Root analysis system （WinRHIZO Pro. 2004c） was used to characterize the root systems. It was found that Alternanthera philoxeroides （Mart） Griseb, Triarrhena sacchariflora （ Maxim. ） Nakai, Cyperus rotundus L. , and Cynodon dactylon （L.） Pers. had higher mean root/shoot ratio, while Arundinella anomala Steud. and T sacchariflora had larger root length density （RLD） and root surface area density （RSAD）. Soils containing roots exhibited smaller soil erosion rate obviously. A. philoxeroides, T. sacchariflora and A. anomala had signifi- cantly higher anti-erodibility enhancement coefficient （Eo） than the other three plants, with Eo presenting good linear relationship with RLD and RSAD. As to roots of different sizes, roots with D ≤ 2 mm were closely related with soil anti-erodibility, and their RLD and RSAD showed good linear relationship with Ec. This relation got weaker as the root diameter increased it was demonstrated that all six plants enhanced soil anti-erodibility significantly, in which A. philoxeroides, T. sacchariflora and A. anomala showed much better effect. It is concluded that RLD and RSAD are good indexes to characterize soil anti-erodibility, especially RLD and RSAD of roots with D ≤2 mm or D ≤0.5mm