5 Conclusion
The results of this study suggest that increases in RFC promote deep distribution of fine roots in the three woody species, mainly owing to the low water and nutrient levels of the coarse soil and penetration into the deep soil layer. High RFC also increased the biomass and length density of fine roots in the soil profile, particularly in the soil layer below 30 cm, which prompted plants to occupy deep soil spaces. With increasing age, the changes in soil structure had a cumulative decreasing effect on fine root vertical distribution; that is, the increasing years of growth reduced the variation ranges in fine root depth and biomass of the three woody species along the RFC gradient. The RFC also influenced the decrease in range of fine root diameter over years, with the greatest range observed under 75% RFC. We also found that interspecific differences in root distribution and the dynamic response to RFC gradient, fine root depth, and biomass of A. vestita decreased with the increase in soil RFC and age, which was inconsistent with the increasing trend in woody species. These results provide insight into the adaptive  processes of plant under rocky soils and have profound management implications for tillage in degraded ecosystems.