科研之友
微信
新浪微博
Facebook
分享链接
摘要
Soil porosity is usually taken as a constant over time for a given field, although in reality it decreases with time after tillage. For the gradient method, estimating soil CO2 production with a fixed porosity may lead to large errors when soil porosity varies over time. In this study, we compared soil air-filled porosity, gas diffusivity, and CO2 production based on a temporally variable soil porosity (phi(V)) with those based on a constant porosity, either initial porosity just after soil tillage (phi(i)) or final porosity at harvest after a tilled soil has settled (phi(f)). Soil porosity was measured seven times during a maize (Zea mays L.) growing season, and an exponential relationship of soil porosity with time was developed to describe phi(V) for the 0- to 5-cm soil layer. Soil CO2 production was estimated from the gradient method and the mass conservation law. Soil-surface CO2 efflux was measured with a dynamic chamber throughout the growing season. The phi(i) value was 0.49 m(3) m(-3) and the phi(f) value was 0.43 m(3) m(-3). Compared with results obtained from phi(V), soil air-filled porosity, gas diffusivity, and CO2 production values obtained from phi(f) were 6, 11, and 22% lower, whereas values obtained from phi(i) were 17, 36, and 70% larger. The soil-surface CO2 effluxes estimated with phi(V) better matched the chamber values than did the estimates with phi(i) or phi(f). We conclude that use of variable soil porosity improves estimations of soil-surface CO2 effluxes and soil CO2 production with the gradient method.
- 出版日期2014-8
- 单位中国农业大学
