Abstract: To investigate the effects of rest grazing on vegetation characteristics and photosynthetic physiology of dominant species in degraded alpine grasslands during greenup period,an alpine meadows with 6-year rest-grazing in the returning green period in Qilian Mountain area was selected for investigation. The results showed that after 6 years of rest grazing in the returning green period,the vegetation coverage,aboveground biomass,underground biomass and soil water content of alpine meadows increased by 38.44%,985.00%,209.56% and 62.62%,respectively,compared with control (no rest grazing);Height,net photosynthetic rate,photochemical quantum efficiency，respiration rate,leaf area,relative chlorophyll content and leaf nitrogen content of dominant grass Elymus nutans Griseb. Leaves increased significantly by 965.77%,139.86%,4.92%,269.37%,254.13%,197.02% and 96.24%,aboveground and underground biomass were significantly correlated with all the indexes except leaf temperature and photochemical quenching coefficient, and leaf net photosynthetic rate was significantly correlated with all the indexes except leaf temperature. Therefore,rest grazing during the greenup period significantly enhanced the photosynthesis and respiration of dominant grasses in alpine grasslands,and promoted plant growth and degraded grassland restoration. This study provided a theoretical basis for the promotion and implementation of grazing rest during greenup period to restore degraded alpine meadows.

Key words: Rest grazing during greenup period, Degraded alpine meadow, Elymus nutans Griseb, Chlorophyll fluorescence parameters, Photosynthesis characteristics, Respiration rate

摘要： 为探讨返青期休牧对退化高寒草地植被特征及优势种光合生理的影响，本研究在祁连山区选择已实施返青期休牧6年的高寒草甸开展了植被特征及优势种光合生理相关指标的调查研究。结果表明：返青期休牧6年后，高寒草甸的植被盖度、地上生物量、地下生物量和土壤含水量较未休牧区分别增加了38.44%，985.00%，209.56%和62.62%，其优势禾草垂穗披碱草（Elymus nutans）株高、叶片净光合速率、光化学量子效率、呼吸速率、叶面积、相对叶绿素含量和叶片氮含量分别提高了965.77%，139.86%，4.92%，269.37%，254.13%，197.02%和96.24%（P<0.05），其地上地下生物量与除叶温和光化学猝灭系数外的指标显著相关，叶片净光合速率与除叶温外的指标显著相关。因此，返青期休牧可显著增强高寒草地优势禾草的光合作用和呼吸作用，促进植物生长及退化草地的恢复。本研究为推广实施返青期休牧这一措施来恢复退化高寒草地植被提供了理论基础。

关键词: 返青期休牧, 退化高寒草甸, 垂穗披碱草, 叶绿素荧光参数, 光合作用, 呼吸作用