ABSTRACT
Organic matter in soils is the complex mixture of organic compounds derived from the dead
and decaying remains of plants, animals, and microorganisms, and their corpses and meta-
bolic wastes at different stages of decomposition. Mineralization of organic carbon (C) is the
conversion from the organic form to inorganic compounds as a result of decomposition
reactions carried out by decomposer organisms, the vast majority of which are microorgan-
isms (bacteria and fungi) (Gregorich et al. 2001). In the process of utilizing soil organic
matter, heterotrophic soil organisms release CO2 during respiration. The release of CO2 as a
metabolic by-product of organic matter decomposition is referred to as C mineralization.
Because soil organic matter is a complex mixture of organic compounds of different
biological origins and at different stages of decay, C mineralization is the result of a complex
set of biochemical processes conducted by a wide range of organisms. Despite the fact that it
is a simplification of the actual process, C mineralization measurements are commonly used
in investigations of soils and the data have a wide range of applications in agriculture,
forestry, ecology, and the environmental sciences. One reason for this is the relative ease
with which CO2 can be measured in the laboratory. There are a wide range of methods for
measuring CO2 production in the field and at the landscape scale, but this chapter is
concerned with measuring C mineralization under controlled laboratory conditions and
only limited reference is made to field methods to illustrate some principles.
