关键词: 落叶松, 净光合速率, 叶绿素荧光参数, 氮, 磷

Abstract: The community characteristics of mixed grassland with 3-year old perennial grasses were studied in Jingqianghe region, one of the alpine regions on Tibetan Plateau. The results showed that cultivated grasses turned green on the 20th of April, 15d earlier than natural grasses, and became mature on the 15th of September, 10d later than the natural grasses, thus the growing period of the cultivated grasses was prolonged 25d compared with the natural grasses. The coverage, photomass and the basal conditions of the alpine grasslands were improved by establishing mixture grassland of perennial grasses in this region. In 9 combinations of the grasses, Elymus nutans and/or Clinelymus nutans dominated the communities. All the grass communties can be assorted as E. nutans or C. nutans single dominated communitires, and E. nutans and C. nutans co-dominated communities. The growth rate dynamics of the communities followed reversed "V" or "U" patterns, with average growth rate of the communties varied from 0.55～0.70 cm·d^-1 in growing season. With increasing numbers of the grass compositions, the diversity and abundance of the cultivated community increased, although the eveness decreased. The similarity of different communities increased with the overlap extent of the grass compositions of the communities.

Key words: Larix gmelinii, Net photosynthetic rate, Chlorophyll fluorescence parameter, N,P