Salix×Aureo-pendula Root System Distribution And Tensile Mechanical Properties In Soil Bioengineering Revetment

In order to understand the effect of different soil bioengineering technique onroot system distribution and tensile mechanical properties, root biomass distribution investigation and tensile tests were conducted on Salix×aureo-pendula roots from four five-year soil bioengineering revetment as rooted cutting, live staking, fascines and brush mattress in experimental base located at Liuli River in Huairou District, Beijing. All tested roots were devided into different diameter classes and soil layer to measure and analysis. The results show that:(1) Root system concentrates in 0-40cm soil layer and and below 40cm soil layer distribution is less.The root system distribution has greatest density in 0-20 cm soil layer in brush mattress and fascines. The biomass distribution is more uniformin 0-40cm soil layerin rooted cutting and live staking. There was the greatest root biomass in brush mattressas it is believed to be rich in ≤1 mm roots,the percentage of the total according to the arranged from high to low in order:brush mattress (31.3%) and fascines (19.2%), live staking (13.5%), rooted cutting (12.8%).(2) The specific root lengthand root length density decreased exponentially with the increase of soil depth in the four kinds of soil biological engineering measures.In 0-20 cm soil layer, the specific root length in different soil bioengineering technique were in follow order:brush mattress (38.92m/g) and fascines(33.61m/g), rooted cutting(11.12 m/g), live staking(10.25m/g).The root length density is arranged from big to small in turn is:brush mattress (8336.62 m/m3) and fascines (7621.53 m/m3), live staking (4600.39 m/m3) and rooted cutting (4456.71 m/m3).(3) The root tensile force increased with the increasing root diameter at the level of power function in all soil bioengineering technique. In 0-20cmlayer, the average tensile force from the largest to the smallest:rooted cutting(0.4085kN), live staking(0.2107kN), fascines(0.1435kN), brush mattress(0.1107kN). But the most deformation in different soil bioengineering technique were in follow order:brush mattress> fascines>live staking> rooted cutting. When the soil depth reached below 20cm, there is not obvious differencein both the root tensile force and the most deformation.(4) Of plant roots to improve soil resistance to disintegration, made a great contribution. Disintegration rate from fast to slow was in the order of rooted cutting, live staking, fascines and brush mattress. The soil disintegration rate had no significant difference in different soil biological engineering measures in the soil depth of 20-40cm.(5) By principal component analysis it was concluded that the order of the different soil biological engineering measures in the aspect of improving soil stability and the comprehensive effect of slope protection was brush mattress(0-20cm)>fascines(0-20cm)>live staking(0-20cm)>rooted cutting(0-20cm)> live staking(below 20cm)>brush mattress(below 20cm)> rooted cutting(below 20cm)>fascines(below 20cm).(6) Depending on the results, four soil bioengineering technique can bedivided intotwoclasses: rooted cutting and live staking can be established on bank to increase the slope stabilization effects ofdeeper layer; brush mattress and fascines shape to the area near the water to alleviate lossoftopsoil.