Distribution and tensile mechanical properties of Salix × aureo-pendula root system in soil bioengineering revetment

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.