Effects of different fertilization on species composition,plant diversity and productivity were discussed to explore the optimum improved practice of degraded grassland in alpine grassland in Northern Tibet.The results showed that the aboveground biomass under the treatment of fertilization was increased by 23.6%-199%compared with no fertilization(CK).The aboveground biomass under the treatments of NP and ONP were 2.99 and 2.11 times of CK and had reached significant level.Even though it improved grassland ...