摘要：
为探讨PAM(聚丙烯酰胺)和草类根系对荒坡紫色土物理性质与抗剪性能的影响,选取荒坡紫色土为研究对象,制备了单施PAM、单植草类和“草类+PAM”等试验处理,采用WinRHIZO(Pro.2004c)根系分析系统和ZJ型应变控制式直剪仪分别测定根系指标和土壤/根-土复合体抗剪强度,结合土壤基本物理性质指标,分析了各处理中PAM、草类根系、土壤物理性质及抗剪性能间的关系.结果表明:1)上述处理均能够显著提高土壤通气持水能力,其中“草类+ PAM”对土壤孔隙度和含水率的改善效果最好,其次是单植草类;2)各处理的大粒级范围(1～0.25mm、0.25～0.05 mm)微团聚体含量增加,小粒级范围(＜0.01 mm)的则减少;3)较之CK,单植草类和“草类+PAM”可使土壤内摩擦角Φ平均值分别提高37.12％和36.59％,黏聚力c平均值分别提高69.47％和83.64％,且根表面积密度(RSAD)和0.7 mm＜d≤0.9 mm(d为根系直径,单位:mm)分别是影响土壤抗剪性能的主要因子和关键径级;4)PAM对草类根系生长有较明显的促进作用,液施PAM能够使狗牙根的平均根长密度(RLD)/根表面积密度(RSAD)/根体积密度(RVD)/根重密度(RWD)增大15.57％～53.16％,三叶草的增大23.02％～80.00％.%We studied the effects of polyacrylamide (PAM) and the grass root system on the shear strength and physical properties of purple soil on barren slopes.Three different treatments were applied to purple soil on barren slopes:PAM (single application of PAM),grass (single planting of grasses),and grass +PAM.The root parameters were measured using the WinRHIZO (Pro.2004c) root analysis system and soil shear strength of soil samples was determined using a ZJ-type strain-controlled direct shear apparatus.We also determined the basic physical properties of soil samples.The main results were as follows∶ 1) All three treatments significantly improved the soil water holding capacity.The grass+PAM treatment had the best effects on soil porosity and water content,followed by the grass treatment.2) All three treatments significantly increased the abundance of microaggregates in the 1-0.25 mm and 0.25-0.05 mm size ranges,and decreased the abundance of those in the smaller size category (＜0.01 mm).3) The average internal friction angle of grass was 37.12％ and 36.59％ higher in the grass and grass+PAM treatments,respectively,than in the control,and the average soil cohesion in the grass and grass+PAM treatments was increased by 69.47％ and 83.64％,respectively.The root surface area density and abundance of roots with diameter between 0.7 mm and 0.9 mm were the main factors affecting the shear properties of soil.4) The growth of grass roots was markedly affected by PAM,which increased the average root length density,root surface area density,root volume density,and root weight density of Cynodon dactylon soil samples by 15.57％-53.16％,and of Trifolium repens soil samples by 23.02％-80.00％.
