Relation between climate variables and the aboveground biomass of Thymus mongolicus-Stipa bungeana community in steppe of Ordos Plateau, Inner Mongolia Comparative studies on above ground numerical characteristics and their relationships with soil moisture of two kinds of natural grassland in loess hilly region Study of the Relationship Between Aboveground Biomass of the Artemisia phaerocephala Stipa bungeana Community and Climate Variables at Sandy Grassland in Erdos Plateau