Characteristics of carbon dioxide flux in soil profiles of arid areas in north temperate regions, China.

By an in situ approach of open-sample pole, we studied carbon dioxide flux in the profiles of 4 types of soil, i.e., chestnut soil, sierozem soil, fragmental soil and gray-cinnamon soil.The results were that 1) CO2 flux increased with soil depth at 0-60 cm, and then decreased at greater soil depths.2) Mean soil CO2 flux at 0-70 cm depth was 660 μmol/(m2·h), ranging from-9 076 to 16 988 μmol/(m2·h).A total of 254.6 t/(km2·a) CO2 gas may be released from the soil into the atmosphere if the soil at 0-70 cm depth was exposed to the air because of a change in land use/land cover.3) Soil CO2 flux differed greatly in the soil types, and the amount of CO2 released from forest soils(gray-cinnamon soil and fragment soil) was largert han that from grassland soils(sierozem soil and chestnut soil).4)In the flux-depth curve of each soil type, there was 1-2 turning points which are correlated with soil structure, root distribution and calcium accumulation layer.5) Soil CO2 flux changed as a function of season, which was greater during growing season than other seasons, demonstrating a phenom enon of the soil absorbing CO2 in other seasons.Our results suggest that soils should be treated carefully when breaking the ground, to reduce the release of soil CO2 into atmosphere.