Soil CO2 emissions measured by closed chamber and soil gradient methods in dry dipterocarp forest and sweet sorghum plots

Abstract

Soil respiration as a major component of the carbon cycle has received considerable attention because of its role in amplifying global warming and in climate feedbacks of ecosystems. This makes it important for us to devise reliable methods in order to measure soil CO2 effluxes accurately. In this study, we investigated the variations of CO2 effluxes for 93 days in sweet sorghum plots and a dry dipterocarp forest by closed chamber and soil gradient methods. The results show that both sites had similar patterns of soil CO2 emission but CO2 emission from the sweet sorghum plots was 4 times higher than from the dry dipterocarp forest. Over the study period, the average soil CO2 efflux and accumulative emission from the dry dipterocarp forest were 360±129 mg CO2 m-2 h-1 and 34 g CO2 m-2 and from the sweet sorghum plots they were 2456±614 mg CO2 m-2 h-1 and 235 g CO2 m-2, respectively. Continuous and high temporal-resolution measurements based on the soil gradient method also enabled us to detect the response of soil CO2 efflux to environmental drivers. We found that rainfall and irrigation events in a short time period could significantly enhance the magnitude of soil CO2 effluxes. In addition, we also found that an appropriate time for daily soil CO2 measurements was around noon.