Interspecific Association of Medicinal Herbs in Ziwuling Region Soil microbial biomass nitrogen and carbon, water soluble nitrogen and carbon under different arbors forests on the Loess Plateau Species Diversities of Major Communities in Malan Forest Region of the Loess Plateau Comparison of the Attributes of Natural Forests and Plantations in Ziwuling Mountain Organic carbon storage in the vegetation biomass in secondary forest region of Ziwuling Mountain