Forest inventories of greenhouse gases and
the carbon sink
Metla evaluated forest emissions of greenhouse gases (GHG) and
the effects of the activities to treat the GHG status required by
the Kyoto Protocol for the period ending 2040. The information will
be needed when the Council of State decides whether the carbon sink
will be taken into consideration already in the first national calculation
of the GHG emissions concerning the period 2008-2012.
Studies made by Metla and the European Forest Institute (EFI) indicate
that changes in soil carbon balance are slower than the ones in
forest carbon. Soil contains an average of one million tons of accumulated
carbon, while the amount stored in forests can be as much as three
million tons. The carbon pool in forests has grown from 500 million
to 740 million tons, primarily due to intensified forest management.
Significant variation has been observed in carbon sinks, depending
on the year and cutting volumes. Warm weather increases the decomposition
rate of litter and reduces the soil carbon sink.
In contrast, favourable weather conditions accelerate tree growth
and strengthen the forest carbon sink. Cuttings reduce the carbon
sink, but the cutting residue remaining in soil induces temporary
increase of the soil carbon sink. The new calculation method helps
to gain a more reliable estimate of the forest carbon budget and
provides a tool for assessing the carbon sink in drained peatlands.
The annual variation of growth caused by weather is taken into
consideration in the calculation, and specifications are made regarding
biomass estimates in growing and thinned stands. To evaluate the
soil carbon sink, litter produced by vegetation is calculated on
the basis of the NFI data and a simulation model is then used to
estimate the underground decomposition of the litter.
Extensive and reliable evaluation of forest carbon sinks is important.
According to the UN Integrated Monitoring of Air Pollution, all
countries shall annually report on not only their carbon budget
of tree stands but also their other forest carbon pools and fluxes.
Together with the other EU countries, Finland has made a commitment
to regenerate the national forest carbon calculation to comply with
the international requirements by the end of 2005. Additionally,
in accordance with the Kyoto Protocol, more exact reporting of changes
of land use and related changes of carbon pools is required.
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Substituting reduced emissions with
carbon sinks requires more extensive inventory calculations
of the forest carbon balance. Until today, reporting on forest
carbon sinks has only covered tree stands, although the biggest
carbon pools are in soil. In the Academy of Finland Research
Programme on Sustainable Use of Natural Resources (SUNARE),
Metla and EFI developed a calculation method that can be used
to estimate the forest carbon balance in conjunction with
the carbon balance calculation of tree stands. The first national
estimate of soil carbon balance was completed.
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