Temporal Variation of Soil CO2 Efflux on Sloping Pasture of Heihe River Basin and Effects of Temperature and Soil Moisture on it

Abstract

Employing LiCor 6400 gas exchange analyzer and soil respiration chamber attachment (LiCor Inc., Lincoln, NE, USA), this paper continuously measured the soil surface CO2 effluxes on the sloping pasture of Heihe River basin from early April to late October 2010 to investigate the soil CO2 efflux rate and its feedback to the changes of climate and land use. The results showed that during the growing season, the diurnal variation of pasture soil respiration in the mountain watershed of the Heihe River valley was low at night, with lowest appears at 7:00, 6:30, 5:30, 5:00, 6:00 and 7:00 from May to October, and started to rise rapidly during 7:00~8:30, and then descend during 16:00~18:30. The maximum soil CO2 efflux appears at 15:00, 14:30, 14:30, 13:30, 14:00 and 15:00. The maximum of average soil CO2 efflux occurred in July and August, and the second was in May and September, and the third was in April and October. And it was basically consistent in April and October. The diurnal average of pasture soil CO2 efflux was between 0.31~6.98?mol m-2s-1, and the Q10 value is 2.16. Soil CO2 efflux had an exponential and Boltzmann correlation with temperature and soil moisture, respectively.