Biomass, Carbon Accumulation & Climate Change

Tropical forests absorb more CO2 through photosynthesis than they emit by respiration. Recent research has quantified this ‘sink’ at about 1.3 gigatonnes of carbon (GtC) per year, equivalent to 16.6% of carbon emissions from the cement industry and fossil fuels combined. It constitutes 60% of the sink provided by all of Earth's terrestrial vegetation. Although forest restoration won't reverse global warming, it may help to slow it down, whilst the shift from carbon-based to carbon-neutral economies proceeds.

About 47% of tree biomass is carbon. Because storing carbon in forests is a valuable service to society, in terms of reducing global climate change, it is worth a great deal of money, in the form of "carbon credits". For example, Kanlayarat Jantawong recently showed that carbon credit profits, from forest restoration by the framework species method, could be worth 16 times more than profits from corn cultivation ... if farmers could access to equitable carbon-credit markets. So, carbon credits could not only cover restoration costs, but they could also provide a powerful financial incentive, for local people to shift from damaging forms of agriculture to more sustainable forestry. This would provide many additional environmental benefits, such as watershed protection and biodiversity conservation. Carbon-credit payments are based on the quantity of carbon stored. So, measuring carbon storage during forest ecosystem restoration is essential.

Relationships between tree size and the carbon they store are well known. They are expressed as "allometric equations". So, to estimate the amount of carbon in trees, tree girth and height are measured and the data are fed into allometric equations. Adding wood density data greatly increases the accuracy of such calculations. For northern Thailand, Titinun Pothong developed new allometric equations, specific for the tree species and climatic conditions of the region. For other areas, general equations are recommended by the International Panel on Climate Change.

Carbon also accumulates in soil, as the trees grow, drop their leaves and die. PhD student, Nuttira Kavinchan developed accurate ways to measure this and excellent equations to predict soil carbon down to 2 m from sampling soil near the surface. 

Full details of how to measure carbon accumulation during forest restoration are provided here.

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