Soil respiration is the measure of carbon dioxide (CO2) which
is released from soil due to the decomposition of soil organic matter by soil
microbes and respiration from plant roots and soil fauna. Soil respiration is
the second largest terrestrial carbon flux. Soil respiration is an extremely
important indicator of soil health because it indicates the level of microbial
activity, soil organic matter content and its decomposition. Microorganisms in
soil are an essential component which affects soil structure and fertility.
Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of
these groups has characteristics that define them and their functions in soil. i.e.
nitrogen fixing bacteria. Up to 10 billion bacterial cells inhabit each gram of
soil in and around plant roots, a region known as the rhizosphere. In 2011,
a team detected more than 33,000 bacterial and archaeal species on sugar beet roots.
The composition of the rhizobiome can change rapidly in response to
changes in the surrounding environment. In a consistently changing Environment
it is essential that the study of changing temperatures, precipitation rates
and CO2 levels and their effect on soil respirations as food production is
heavily dependent on the use of fertile soils. The amount of soil respiration
is an indicator of nutrients contained in organic matter being converted to
forms available to crops (e.g., phosphate as PO4, nitrate-nitrogen as NO3, and
sulphate as SO4). High soil respiration rates are not always better as they may
indicate an unstable system with the loss of soil organic matter due
potentially to excessive tillage or other factors which may degrade soil
health. The rate at which CO2 moves from the soil to the atmosphere is
controlled by the rate of CO2 production in the soil, the strength of the CO2
concentration gradient between the soil and the atmosphere, and the properties
such as soil pore size, air temperature and wind speed that influence the movement
of CO2 through and out of the soil. Soil respiration in terrestrial ecosystems
is estimated to total 50-75 Pg C/yr and with fossil fuel burning by comparison
producing 5 Pg C/yr to the atmosphere even a small change in soil respiration
flux may rival the annual fossil fuel loading of atmospheric CO2.
Q10 is a measure of the temperature sensitivity of an
enzymatic reaction rate or a physiological process due to an increase by 10°C.
Discontinuities are indicating physiological perturbations. Most Q10-values are
around 2 and reflect a doubling of molecules with an energy higher than the
activation energy that is required for an enzymatic reaction to occur.