Fig. 4. Content and stoichiometric characteristics of organic carbon, total nitrogen, and total phosphorus in plant root and aboveground fractions and rhizosphere soils for different plant species. Error bars refer to standard deviation; respectively. Different lowercase letters indicate significant differences among different plant species (p<0.05). Fe, Festuca elata ; Ed, Elymus dahuricus ; Ms, Medicago sativa ; Fe+Ed, Festuca elata plus Elymus dahuricus ; Fe+Ms, Festuca elata plus Medicago sativa ; Ms+Ed, Medicago sativa plus Elymus dahuricus ;Fe+Ms+Ed,Festuca elata plus Medicago sativa plus Elymus dahuricus .