Effects of alfalfa planting with different cultivating ages on abundance of soil carbon-sequestration bacteria and labile organic carbon fractions in rainfed Loess Plateau

• CAI Xuemei, 
• PAN Zhandong, 
• LUO Zhuzhu, 
• LI Lingling, 
• NIU Yining, 
• CAI Liqun, 
• LIU Jiahe