Genotype and Planting Density Effects on Rooting Traits and Yield in Cotton (Gossypium hirsutum L.) Fine root distribution characteristics of sabina vulgaris and Artemisia ordosica communities in the Mu Us Sandland of Inner Mongolia, China CHARACTERIZING ROOT GROWTH AND SPATIAL DISTRIBUTION IN COTTON DISTRIBUTION CHARACTERISTICS OF ROOT AREA OF SABINA VULGARIS UNDER DIFFERENT HABITATS