COMPARISON OF METHODS TO MEASURE SOIL RESPIRATION

Soil respiration measurements obtained using five techniques were compared over several growing seasons. The soil carbon dioxide profile method gave the highest values, those of the dynamic-chamber method (continuous analysis of carbon dioxide in flowing air) usually being lowest and those of the above-canopy micrometeorological method being intermediate. Most methods showed the soil respiration increasing from about 50 milligrams of carbon dioxide per square meter per hour at the beginning of the growing season to a peak in late July to early August, followed by a decline to near 20 milligrams by late September. The soil-carbon dioxide and static-chamber (alkali absorption) methods agreed closely. Differences between methods were explained by: Inaccuracies in determining transfer coefficients for carbon dioxide, differences in the component fluxes of total soil respiration, which each technique included, disturbances to the system caused by the method, such as removal of green shoots, and sampling errors. © 1979 The Williams & Wilkins Co.