Root structure of slope protection plants in a high-grade highway

Root length and root length density of Lespedeza bicolor,Amorpha fruticosa,and Sea buckthorn were investigated in a country highway-TongSan highway（Tongjiang to Sanya） in Heilongjiang Province,China.The root lengths were divided into five root orders according to Pregizter sequence classification method.Results show that sea buckthorn roots are dominated by coarse roots in the horizontal growth,while L.bicolor has a large proportion of fine roots in vertical conical growth and A.fruticosa is in depth growth.Root length density of L.bicolor in all the root sequences is higher than that of sea buckthorn and A.fruticosa.On the basis of the root structure,it is inferred that L.bicolor roots mainly absorb the surface soil moisture for its normal growth;in contrast,A.fruticosa has good uptake ability to deep soil water.The root structure of sea buckthorn implies that it has a strong drought resistance.