Abstract: The thermal transportation and carbon budget in alpine meadow of Qinghai-Tibetan Plateau are highly sensitive to climate change, but little research was made about the influence of precipitation because of its complicacy. Based on the data measured by three-dimensional ultrasonic anemometer and fast-response open-path infrared CO₂/H₂O analyzer, the effects of one precipitation process from 8-17 August, 2002 on the thermal transportation and CO₂ flux in alpine meadow of northeastern Qinghai-Tibetan Plateau were analyzed. The results showed that the precipitation process decreased the air temperature, soil temperature, total radiation, surface reflected radiation, photosynthetically active radiation (PAR), net radiation, soil heat flux, latent heat flux, and sensible heat flux by 23.3%, 23.1%, 61.9%, 58.9%, 61.7%, 57.9%, 268.3%, 61.6%, and 71.0%, and increased the atmospheric humidity and CO₂ flux by 27.0% and 38.6%, respectively. Precipitation weakened the influence of PAR on the daytime net CO₂ exchange (NEE) of the alpine meadow ecosystem, but enhanced the effects of soil temperature on nighttime respiration. Precipitation intensity had no significant influence on the daytime NEE, but decreased the nighttime respiration.

Key words: Polytrichum juniperum, Mire, Clone, Innate annual marker, Age structure