Carbon sequestration
Carbon sequestration is the accumulation of carbon by forest stands. This is a dynamic process in which carbon atoms are continually exchanged between the atmosphere and the trees. Over the lifetime of the stand more carbon
is captured than is released so there is a net accumulation in the forest.
Whilst carbon is being accumulated in the tree biomass
and the soil we describe that forest as a 'sink'.
There comes a point in the life of a forest when 'equilibrium' is reached, hence the quantity of carbon accumulated by a forest is finite. At this point we describe the forest as a 'reservoir' that holds 'carbon stock'.
When there is a net transfer of carbon to the atmosphere, (eg if the forest is destroyed) it is referred to as a 'source'.
In a newly established forest the rate of sequestration is slow. It peaks through the full-vigour growing years, then slows again as the forest reaches maturity and equilibrium. Fast-growing stands in the UK can typically sequester 10tC/ha/yr (10 tonnes of carbon per hectare per year) although over a full commercial rotation this may average 3tC/ha/yr.
Carbon stock in above-ground biomass may typically reach 160tC/ha. Thus, over successive rotations, the average stock of the site may be 70tC/ha. Forest soils may contain more carbon than the trees themselves, with inherent carbon content before planting plus that sequestered by the growing forest. Typical UK forest soil values range between 220-600 tC/ha; arable soils by comparison will typically contain 150tC/ha.
is captured than is released so there is a net accumulation in the forest.
Whilst carbon is being accumulated in the tree biomass
and the soil we describe that forest as a 'sink'.
There comes a point in the life of a forest when 'equilibrium' is reached, hence the quantity of carbon accumulated by a forest is finite. At this point we describe the forest as a 'reservoir' that holds 'carbon stock'.
When there is a net transfer of carbon to the atmosphere, (eg if the forest is destroyed) it is referred to as a 'source'.
In a newly established forest the rate of sequestration is slow. It peaks through the full-vigour growing years, then slows again as the forest reaches maturity and equilibrium. Fast-growing stands in the UK can typically sequester 10tC/ha/yr (10 tonnes of carbon per hectare per year) although over a full commercial rotation this may average 3tC/ha/yr.
Carbon stock in above-ground biomass may typically reach 160tC/ha. Thus, over successive rotations, the average stock of the site may be 70tC/ha. Forest soils may contain more carbon than the trees themselves, with inherent carbon content before planting plus that sequestered by the growing forest. Typical UK forest soil values range between 220-600 tC/ha; arable soils by comparison will typically contain 150tC/ha.
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