The use of soda-lime for measuring respiration rates in terrestrial systems

Abstract

A granular mixture of sodium hydroxide and slaked lime, was tested as a potential alternative to alkali solutions for absorbing carbon dioxide (CO/sub 2/) as an indicator of soil respiration rates. Because soda-lime can be used as a solid, problems with freezing and spillage are eliminated. Also, no titration is necessary; the only measurement needed is the dry weight of the soda-lime before and after the absorption period. A 0.2 N solution of potassium hydroxide (KOH) absorbed 38% as much CO/sub 2/ as soda-lime measured simultaneously under identical field conditions and only 22% as much in the laboratory. In the field, variability between plots was much greater with soda-lime than with KOH. However, this variability was apparently a reflection of actual spatial variability of soil CO/sub 2/ efflux, because under homogeneous conditions in the laboratory variability was quite low (SD ca.8% of the mean) and about the same for both KOH and soda lime. In field plots, greater proportional increases in net CO/sub 2/ absorptive capacity were produced by increasing the weight per unit surface area than by increasing the surface area per unit weight. No significant (P<0.01) increase in net CO/sub 2/ values was observed with soda-lime surface exceeding 32 cm/sup 2/ (5% of the measured forest floor surface) and amounts greater than 30 g.