土壤CO_2浓度昼夜变化及其对土壤CO_2排放量的影响

对石林地区两个研究点土下20、40和60cm土壤CO2浓度和土壤CO2排放量的昼夜变化进行的研究表明二者之间具有一定的正相关关系,因此土壤CO2排放量除受环境因子影响之外,还受土壤CO2浓度所控制。土壤CO2浓度和土壤CO2排放量之间的相关关系可以用来解释土壤有机碳含量及温度对土壤CO2排放量的影响,即土壤有机碳含量高和温度升高是通过影响土壤空气中CO2的形成速率,导致土壤CO2浓度升高,从而促进土壤CO2的排放。

Diurnal Variation of Soil CO2 Concentration and Its Relationship with Soil CO2 Flux

Diurnal variation of soil CO2 concentration and flux of red soil and their relationship were studied in June of 2002 in Shilin national park,Yunnan provice. Study shows that in different depth, soil CO2 shows fluctuation during 24 hours. From 18:00 to 22:00, concentration of soil CO2 decreases (for example, at subsoil 20cm, soil CO2 concentration decreases from 0.48% at 18:00 to 0.43% at 22:00). From 22:00 o’clock to next 6:00 o’clock, soil CO2 concentration shows a minor fluctuation, and reaches the minimum at 6:00 o’clock. During daytime, from 6:00 to 18:00, soil CO2 concentration increases steadily and at 16:00 o’clock, it reaches the maximum of the whole day. Then it begins to fall down. In site A, soil CO2 concentration increases with soil depth. But it is a different case in site A’ because of the disruption of the soil, which doesn’t shows the same variation. Sometimes soil CO2 concentration at 20cm depth is greater than that of at 60cm depth. Study result also shows that soil CO2 flux coincides with soil CO2 concentration at 20cm, 40cm and 60cm. Soil CO2 concentration and flux is higher during daytime than that of night. The positive relationship between soil CO2 content and soil CO2 flux gives good explanation to the relationship between the soil organic carbon content, temperature with soil CO2 flux. Soil CO2 concentration in different soil depth increase with higher production of soil CO2 because of higher soil organic carbon content and increasing temperature. As this study shows, Soil CO2 flux will increase when soil CO2 concentration increases.