中文摘要：

为探讨水土保持先锋物种香根草的培肥效应及其与各径级根系指标间的关系,以裸地为对照,定期分0～10cm,10～20cm,20～30cm 土层采集土壤和根系样品,常规方法测定土壤有机质、氮、磷、钾的全量和速效养分,WinRHIZO（Pro.2004c）根系分析系统分10个径级测定根系参数（根长、根表面积和根体积）.结果表明：香根草的培肥效应主要体现在有机质上,且此效应随香根草定植时间的延长而增强,其次是全氮,而有效磷和速效钾则出现亏损;香根草小区土壤有机质、有效磷、全钾、速效钾均表现出明显的土壤养分表聚现象,在0～10cm 土层的含量显著大于其他土层的（P〈0.05）;0.00mm〈d≤2.00 mm（犱为根系直径）是影响土壤有机质含量的主要根径范围,该范围内所有径级的根长密度/根表面积密度/根体积密度均与土壤有机质含量极显著正相关（P〈0.01）,尤其是径级0.00mm〈d≤0.50mm,其次是径级1.50mm〈d≤2.00 mm;d=2.00 mm 和d=4.50 mm 是重要分界线,当0.00mm〈d≤2.00mm 时,香根草各径级的所有根系指标在土层间均表现出显著性差异且与土层深度极显著负相关,其中0.50mm〈d≤1.00mm 径级的相关系数值最大,当2.00mm〈d≤4.50mm 时土壤养分与所有径级的根系指标均无显著性相关;根重密度/根长密度/根表面积密度/根体积密度的最大值均出现在0～10cm 土层,且根长密度在年际间、土层间均表现出显著性差异.

英文摘要：

The aim of this study was to determine the effects ofVetiveria zizanioides plants and their roots on soil properties,and define the role of different root diameter classes.The research was conducted in the Purple Soil Area of China.The experiment compared bare control plots with plots planted inV .zizanioides .Soil and root samples were collected regularly from 0-10 cm,10-20 cm,20-30 cm soil layers.Contents of soil or-ganic matter,total and available nitrogen,phosphorus,and potassium were measured by conventional meth-ods.Roots were divided into 10 diameter classes measured by a Root Analysis System (WinRHIZO,Pro. 2004c).It was found that:1)V .zizanioides substantially enhanced the accumulation of soil organic matter, the longer the planted time the greater the effect.V .zizanioides also promoted the accumulation of soil totalnitrogen,but the effect was weak compared with organic matter.Both available phosphorus and potassium were depleted in allV .zizanioides plots.2)The levels of organic matter,available phosphorus,total potassi-um and available potassium showed topsoil accumulation in allV .zizanioides plots;i.e.over time their levels in the 0-10 cm soil layer increased significantly more than in the 10-20 cm and 20-30 cm soil layers (P <0.05).3)The root diameter range (d)0.00 mm