Analysis of soil nitrogen dynamics of Medicago sativa and Leymus chinensis pasture in the Songnen Plain

• Chao GAO, 
• Yue-xue ZHANG, 
• Ji-shan CHEN, 
• Gui-li DI, 
• Duo-feng PAN, 
• Jian-li WANG, 
• Xin-tong KANG, 
• Qiang ZHANG, 
• Peng ZHONG