北温带干旱地区土壤剖面CO2通量的变化特征

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

采用开放式样杆方法,对干旱土纲的4种土壤类型(栗钙土、灰钙土、粗骨土、山地灰褐土)进行土壤剖面CO2通量的观测研究,结果表明:1)在0～60cm深度范围内土壤剖面CO2通量随土壤深度的增加而增加,60cm为转折点,之后,随土壤深度的增加而减小。2)土壤剖面CO2通量平均值为660μmol/(m2·h),在-9076～16988μmol/(m2·h)范围内变化,如果土地利用/土地覆盖发生改变(0～70cm深度),将可能有254.6t/(km2·a)CO2从土壤向大气释放。3)土壤种类不同,CO2通量明显不同,森林土壤释放量大于草原土壤。4)在通量-深度曲线中,各土壤类型均出现1～2个拐点,变化原因与土壤剖面结构和根系分布有关,钙积层的有无、厚度起决定作用。5)存在季节变化,植物生长季节的CO2通量远大于其他季节,其他季节可能存在土壤吸收CO2现象。因此,应避免在植物生长季节施工动土,以减少土壤CO2向大气中释放。

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/（m^2·h）, ranging from-9 076 to 16 988 μmol/（m^2·h）.A total of 254.6 t/（km^2·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.