摘要
在次降雨过程中,生物埂土壤内部经历了干燥-湿润-再干燥的干湿循环过程,对生物埂坎土壤抗剪强度和稳定性造成潜在影响;本文主要研究次降雨后干湿作用对桑树生物埂土壤抗剪强度衰减-恢复效应。采用根系挖掘法、室内直剪试验和土壤理化性质分析等综合性研究手段,全面研究了桑树生物埂根系分布、在次降雨前后(降雨第0~9天)干湿循环过程中生物埂土壤理化变化及抗剪强度响应特征、根系对土壤抗剪强度增强效应。结果表明:(1)不同径级根系随土层深度变化显著,根径级≤1mm的根系集中于土层深度较浅(0~20cm)位置,而2mm<根径级≤5mm的根系在较深层次(20~40cm)土壤中穿插生长。(2)桑树生物埂土壤垂直层次土壤容重、土壤孔隙在次降雨前后均存在显著差异(P<0.05)。除30~40cm土层外,土壤容重在经过一次干湿循环作用后有所增加,增加幅度为5.47%~5.88%,且在第5天时土壤容重达到最大值(各层次依次为1.39,1.37,1.44g/cm3);土壤总孔隙度、毛管孔隙度随干湿作用时间呈现先增大后减小的趋势,在第1天(峰值点)发生转折变化。(3)生物埂土壤粘聚力和内摩擦角随着含水率增加呈现出一阶指数衰减变化,各层次土壤粘聚力和内摩擦角在干湿作用过程呈现出先衰减后恢复的"V"型变化趋势;粘聚力与含水率的相关系数为0.68,内摩擦角与含水率的相关系数为0.73。(4)桑树生物埂不同根系径级土体的粘聚力、内摩擦角和抗剪强度与根长密度和根表面积密度呈正相关关系,相关系数在0.30~0.79之间。土壤粘聚力和内摩擦角随含水率增加呈线性衰减的趋势,在次降雨前后生物埂土壤容重、土壤孔隙特征表现为显著性变化;土壤粘聚力和内摩擦角的变化与根长密度、根表面积密度呈正相关关系。生物埂能够改善土壤结构及其土壤通气性,提高土壤养分含量,降低土壤容重,增加土壤孔隙度,为
During rainfall the soil in bio-embankments undergoes a drying-wetting-re-drying process which may potential influence the shear strength and stability of bio-embankment soil.This study investigated the attenuated recovery of soil shear strength in a mulberry bio-embankment under drying-wetting conditions.The main purpose of the study was to undertake a comprehensive study of mulberry hedge root distribution before and after rainfall(rainfall 0-9d),the wetting and drying process in bio-embankment soil,physicochemical changes and the influence of roots on soil shear strength.The results show:(1)Roots with root diameter≤1mm were concentrated at shallow depths(0-20cm),while the roots with 2mm <root diameter≤5mm were mostly found at 20-40 cm soil depth.(2)There were significant differences(P<0.05)in soil bulk density,soil porosity and soil water of different vertical layers before and after rainfall.In the 30-40 cm soil layer soil bulk density increased after a dry-wet cycle by 5.47%-5.88%,reaching a maximum value 5days after wetting(1.39,1.37,1.44g/cm3).Soil porosity initially increased and then decreased during a dry-wet cycle.(3)Soil cohesion and internal friction angle responded to an increase in soil water content;initially there was a large decrease in both traits.The correlation between cohesion and soil water content was 0.68,and the correlation between internal friction angle and soil water content was 0.73.(4)Mulberry root diameter classes influenced soil cohesion,internal friction angle and shear strength.Root length density and root surface area density were significantly,positively correlated.Soil cohesion and internal friction angle showed a linear decreasing trend with increasing soil water content.Bio-embankments can improve soil structure,soil aeration,soil nutrient content and reduce soil bulk density,and increase soil porosity,crop growth,development and yield on sloping land.
出处
《草业学报》
CSCD
北大核心
2017年第6期56-67,共12页
Acta Prataculturae Sinica
基金
公益性行业(农业)科研专项“坡耕地合理耕层评价指标体系建立(201503119-01-01)”
重庆市水利局科技项目“紫色丘陵区面源污染防治措施效应评价(2012)”资助
关键词
生物埂
粘聚力
内摩擦角
抗剪强度
干湿作用
衰减-恢复效应
bio-embankment
cohesion
internal friction angle
shear strength
drying-wetting condition
attenuation-recovery effect
