Effects of Cortical Thickness and Stele Diameter on Variations of Root Diameter in Fraxinus mandshurica and Larix gmelinii Analysis on Asymmetry of Horizontal Lateral Root Diameterin Clonal Ramets of Rhus typhina Difference and inherent linkage of root characteristics in different root classification of Pinus tabulaeformis seedlings Genotype and Planting Density Effects on Rooting Traits and Yield in Cotton (Gossypium hirsutum L.) Morphological Response of Neyraudia reynaudiana Root to Different Phosphorus Stress Root Growth of Quercus variabilis Seedlings in Response to the Environmental Heterogeneity