Measurement and interpretation of the oxygen isotope composition of carbon dioxide respired by leaves in the dark.
The lead emissions of exhaust gases are particularly dangerous in this respect since they occur in the form of minute particles which reach the pulmonary tract in respired air.
Carbon is stored in the soil as organic matter and is respired by plants, bacteria, fungi and animals.
They provide a high discharge ratio near the surface, but the discharge ratio is not fixed either as a proportion of respired volume or mass.
A portion of the respired gas is discharged that is in some way proportional to usage.
Some of the carbon compounds are easily digested and respired by the microbes, resulting in a relatively short residence time.
Dead plant material in or above soils remains there for some time before being respired by heterotrophs.
About half of the gross primary production is respired by plants directly back into the atmosphere.
