[Analysis of the spatial and temporal changes in soil CO2 efflux and its related factors from alpine meadow in Qilian Mountains].

Continuous field experiment was carried out on alpine meadow along different elevation gradient in Qilian Mountains during the growing season of 2004 using a soil respiration chamber (Li-6400-09) connected to a portable photosynthesis system (Li-6400). The possible effect of water-heat factors and root parameter on characteristics of alpine meadow soil respiration was statistically analyzed. The results indicate that soil CO2 efflux has apparent spatial variation laws. Spatial variation patterns of soil respiration from different alpine meadow along elevation gradient are gradually decreased and its coefficient of variation increases gently. The curves of day change of soil CO2 efflux have a simple peak value, and it is low at night, with lowest at 02:00-06:00, and starts to rise rapidly during 07:00-08:30, and then descends during 16:00 -18:30. The peak CO2 efflux appears during 11:00-16:00. The diurnal average of soil CO2 efflux is between (0.56 +/- 0.32) - (2.53 +/- 0.76) micromol x (m2 x s)(-1). As for seasonal variation, soil CO2 fluxes of various are relatively high in summer and autumn but relatively low in spring and winter. The maximum of average soil CO2 efflux occurrs in July and August [4.736 micromol (m2 x s)(-1), and the second is in June and September, and the third is in May and October. Soil CO2 efflux of alpine meadow during growth season is positively correlated with soil temperature, root biomass and soil water content at depths of 10 cm to different degrees. These results indicate that the temperature, soil moisture and root biomass have great effects on the spatial variation of soil CO2 efflux in the area.