Abstract: The effects of habitat and cooling on morphological characteristics, biomass allocation and survival rate of seedlings of six Gramineae species were studied in the eastern QinghaiTibet Plateau, in order to provide basis for understanding growth strategies of alpine plants in different conditions. The results showed that the seedlings of the six species allocated more biomass to shoots to increase competition of light resources when growth conditions were simulated as grassland (covered by vegetation), while the seedlings had higher biomass and growth rate when plants were assumed to grow in bare area. The treatment of cooling in the early stage of seedlings played a significant role in subsequent growth, and the seedlings encountered cooling allocated more resources to the roots. The survival rate of seedlings under conditions covered by vegetation was significantly higher than that under exposed conditions, while the treatment of cooling had no significant effect on the survival of seedlings. Therefore, the six species in this study showed significant morphological plasticity to the changed environmental conditions, and no significant variation in seedling survival to abnormal temperature might be an adaptive selection of plants to adverse alpine environment.

Key words: water source., rocky mountainous area, oxygen isotope, returning cropland to forestland