RATE OF CO_2 EVOLUTION FROM SOIL IN RELATION TO TEMPERATURE AND AMOUNT OF DISSOLVED ORGANIC CARBON

Abstract

Various soils from the Tama basin (Japan), including volcanic and alluvial soils with different vegetations and land-uses, were incubated until the rate of CO_2 evolution showed constant values. The rates of CO_2 evolution Y (mg C/kg dry soil/hr) of the incubated soils were highly correlated with the amounts of dissolved organic carbon (DOC) X (mg C/kg dry soil) in soil solution obtained by the centrifugation (13,000 g, 4℃, 40min) ; and the regression equation, Y=0.298X^<1.09> (sample number n=65,correlation coefficient r=0.954), was obtained at temperature t (℃) 25. Increase in temperature increased the rate Y and vice versa, but did not change the amount X significantly. Assuming that the temperature coefficient Q_<10> is 2,and substituting the base of natural logarithm for e, the regression equation is rewritten as Y=0.053・e^<0.069t>・X^<1.09>, by which the rate Y of any incubated soil in the Tama basin can be predicted from the two factors, temperature t and the amount X. There was good agreement of the predicted rates Y with the measured rates Y of several soils incubated at various temperatures. On the assumption that the DOC was the respiratory substrate for the soil microbes, it was suggested from the equation that the turnover rate of DOC varies with the temperature t and the amount X. For example, the turnover rate per hour at 25℃ was 0.298 (turnover time, 3.36 hrs) when the amount X was 1,and 0.367 (2.72 hrs) when the amount X was 10.