Responses of 12 plant species flowering phenology to nitrogen and phosphorus nutrient additions in alpine grassland of Haibei, Qinghai

• LI Yonghui, 
• YUAN Xuefeng, 
• CHENG Rong, 
• LI Honglin, 
• WU Xuexia, 
• REN Fei, 
• LI Xilai, 
• LI Lanping