To determine the distribution of fine roots of Robinia pseudoacacia mixed forests and pure forest in saline-alkali soils of the Yellow River Delta,fine root distributions in Fraxinus velutina and Robinia pseudoacacia mixed forest,Ailanthus altissima and Robinia pseudoacacia mixed forest and Robinia pseudoacacia pure forest were sampled with a soil column method.The vertical distributions of fine roots in different forest stands were analyzed for the distributions of fine root biomass density,fine root surfa...