Agriculture Reference
In-Depth Information
3.1.2 SPECIFIC ELEMENTS
3.1.2.1
Carbon
While not a nutrient element‚ carbon is a major component of the tissues of all organisms
and is one of the elements most closely associated with life. Indicative concentrations
(dry weight basis) in a range of organisms are (Matsumoto‚ 1976; Bowen‚ 1979;
Anderson and Domsch‚ 1980; Spain‚ unpublished):
bacteria 43 %;
fungi 32-38 %;
marine algae 28-35 %;
terrestrial higher plants
ca.
43 %;
Insecta (whole termites) 17-69 % (equivalent to 45-66 % on an ash free basis);
Insecta (whole ants) 45-60 %;
fish 47 %;
man: muscle 67 %‚ bone 36 %.
Carbon is the vehicle for biological energy transfer within the biosphere at landscape
and ecosystem scales‚ and within organisms. Large stores of this element occur in
the lithosphere (including soils)‚ the biosphere‚ the atmosphere and the hydrosphere.
Mass transfers of carbon occur between the lithosphere‚ the biosphere‚ the seas and other
water bodies and the atmosphere as part of the global carbon cycle (Schlesinger‚ 1997).
The world's carbon stocks are distributed between four reservoirs (Table I.17) three
of which are in dynamic equilibrium with each other. Apart from a small proportion
extractable as fossil fuels (estimated mass 4000 Pg)‚ the large geological reservoir
may be considered as inert (Eswaran
et al.‚
1993). The oceans comprise
ca‚
85 % of the dynamic stocks while the atmosphere contains less than 2 %. However‚
it should be noted that fossil fuel carbon stocks are more than five times the size of
the atmospheric pool.
