Effect of rocky slopes gradient on root growth and pull-out resistance of Lespedeza bicolor Turcz.plants

摘要

This research was carried out to investigate root system distribution characteristics and pull-out resistance of L.bicolor on 40° and 50° and 60° rocky slopes along Jing-cheng Highway(the third phase of the project) in northern China,using dig-out method and hydraulic tension meter.Based on the roots cutting off in the up-slope or down-slope direction,three treatments (T1,T2,and T3)were included in the roots pull-out resistance experiment.The results of this study showed as follows.First,roots branch orders increased gradually,and root length and dry weight declined gradually as slope gradient increased.Second,roots grown in up-slope and on down-slope direction distributed uniformly on 40° and 50° slopes,and the angle of first order roots and the slope were 0～10°.On 60° slope,however,the roots grown in up-slope and down-slope direction did not distribute uniformly,and the angle of first order roots grown in up-slope direction and the slope increased to 30～40°.Third,for the same treatment,there was no significant difference in roots pull-out resistance between the three slopes(P ＞ 0.05).On 40° and 50° slope,there was no significant difference in roots pull-out resistance between that three experiment treatments; however,significant differences in the root pull-out resistance were found between T1 and T3,and between T2 and T3 (P ＜ 0.05) on 60° slope.Finally,the Lespedeza bicolor Turcz.roots pull-out resistance was positively correlated with root length and dry weight,though not statistically significant.