护岸金丝柳根系分布特征和力学特性分析
Distribution and tensile mechanical properties of Salix × aureo-pendula root system in soil bioengineering revetment
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摘要: 了解不同土壤生物工程措施下根系分布特征与抗拉特性对土壤生物工程措施的合理配置意义重大。以竣工5年的北京市怀柔区土壤生物工程试验区4种不同种植方式(埋根、扦插、梢捆、灌丛垫)下的金丝柳根系为研究对象,测量统计不同土层深度、不同径级的根系生物量并进行单根拉伸试验,分析在不同种植方式下金丝柳根系的生物量分布特征和单根抗拉特性,结果表明:灌丛垫和梢捆措施根系主要分布在0~40cm深度的土层中,在0~20cm土层中尤为集中。灌丛垫方式下根径≤1mm的细根含量丰富(占其总量的31.3%),须根系最为发达,梢捆次之,细根含量占其总量的19.2%。不同种植方式下根系抗拉力与直径都呈正相关,且以幂函数的规律变化。在0~20cm的土层中,不同种植方式下根系的抗拉特性存在较大差异,平均抗拉力从大到小依次为埋根、扦插、梢捆、灌丛垫;而平均延伸率从大到小依次为灌丛垫、梢捆、扦插、埋根。所以,灌丛垫和梢捆方式下根系浅层生物量较大,须根发达且具有更好的延伸性能,可有效减轻表土侵蚀,应设置在水位浮动区;埋根和扦插措施下根系能抵抗更大的剪切力,更好地深入土层深处,可设置在岸堤区。Abstract: In order to understand the effect of different soil bioengineering measures on the distribution and tensile mechanical properties of root system, we investigated root biomass distribution and conducted tensile tests on Salix × aureo-pendula roots from four types of soil bioengineering revetment, i.e., rooted cutting, live staking, fascines and brush mattress in the experimental base located at Liuli River in Huairou District, Beijing. All the revetments have been finished for five years. All tested roots were divided into different diameter classes and soil layers for biomass measure and tensile mechanical analysis. The results showed that: root system concentrated in 0-40cm soil layer and root system had the highest density in 0-20cm soil layer in revetments with brush mattress and fascines. There was the highest biomass of roots with diameter less than 1mm in brush mattress measure, accounting for 31.3% of total biomass, followed by that with fascines measure (19.2%). The root tensile force increased with the increasing root diameter in a power function pattern among all bioengineering measures. In 0-20cm layer, the average tensile force had a significant difference, ranking from high to low as rooted cutting>live staking>fascines>brush mattress, while the average ultimate elongation among different measures followed the order of brush mattress> fascines >live staking > rooted cutting. According to our results, the four soil bioengineering measures can be divided into two types: brush mattress and fascines are suitable to be applied to the area near water surface to alleviate loss of topsoil; rooted cutting and live staking can be established on bank slope to increase the slope stabilization of deeper soil layer.