Soil Formation - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 84

VEGETATION CANOPY

CO 2 fixation by
photosynthesis

FOOD, FIBRE, FUEL

Autotrophic
respiration

CARBON
STORAGE

NUTRIENT
TRANSFORMATION

CO 2 production from organic
matter mineralization

BREEDING STOCK AND
GENETIC INFORMATION

CH 4 production from
waterlogged soils

Carbon allocation to roots
and soil fungi networks

N 2 O

NO x

O 2 diffusion into soils
AEROBIC SOILS - carbon mineralization

PLANT LITTER

MICROBIAL BIOMASS
SOIL ORGANIC MATTER

HABITAT AND
BIODIVERSITY

SOIL
EROSION

WATER STORAGE
AND TRANSMISSION

SOIL

- decomposed residue
- mineral - bound residue

WATER TABLE - diffusion barrier
ANAEROBIC WATERLOGGED SOILS
- carbon preservation
- methane production

WATER FILTRATION AND
POLLUTANT ATTENUATION

SOLUBLE ORGANIC CARBON

SOIL FORMATION

REGOLITH

BEDROCK

Fig. 6.2. As soil forms from the regolith, the minerals of the parent material dissolve, contributing solutes to the pore water solution that can be hydrologically
transported from the soil profile. Within the soil profile, secondary mineral phases form by pseudomorphic mineral alteration or precipitation from solution,
particularly micro- and nano-sized fragments of clay minerals and binary oxide minerals of Fe and Al. Organic carbon addition to the saprolite occurs by
deposition of dead plant litter, which is vertically mixed by soil fauna, and through the allocation of photosynthate carbon belowground via root growth, allocation
to microbial root symbionts such as mycorrhizal fungi and as organic exudates. All of these organic inputs provide a carbon and energy source to support
heterotrophic organisms as organic matter decomposers and other functional communities of the microbial ecosystem of the soil. Living organisms bind with
decaying biomass and mineral fragments into larger aggregates, resulting in the development of soil structure - the mass distribution of aggregates by size, also
reflecting the pore size distribution. Thus, soil formation occurs at the reactive interface of Earth's surface where parent material meets plant inputs and infiltrating
water. (From Victoria et al ., 2012.)