Professor Jari Hynynen, a researcher at the Natural Resources Institute Finland, explains the carbon sequestration capacity in various forest stands. Forestry specialist Anne Polojärvi emphasises the importance of soil diversity and site preparation for forest growth.
The forest area will regenerate much faster after harvesting if the site is prepared and planted. The forest will also regenerate naturally, but this process will be much slower.
These conclusions can be drawn by assessing the situation in eight different forest sample plots, which forest.fi visited in the summer of 2022. The aim of the visits was to observe the growth of different types and ages of forest. The sample plots are located in central Finland, in the Käsmä area of Kuusamo municipality, approximately 100 kilometres south of the Arctic Circle.
The sample plots were analysed by Anne Polojärvi, a forestry specialist from the Kuusamo Forest Management Association, who pointed out the peculiarities of the Kuusamo area that affect the forest growth rate. In this highland region, the vegetation zone and the annual temperature sum differ from other areas at the same latitude. The entire Kuusamo territory is located more than 200 metres above sea level, and climatic conditions correspond to those of Central Lapland.
“The annual temperature sum in Kuusamo is about the same as in Sodankylä. Altitude above sea level plays a major role in the growth rate of forests and other vegetation,” says Anne Polojärvi.
Global warming is visible in the north
The annual temperature sum is calculated by adding up the average daily temperatures during the growing season. It includes 24-hour periods when the temperature exceeds five degrees Celsius. Sodankylä is located approximately 200 kilometres north-west of Kuusamo. As in other cold regions, global warming can also be observed in Kuusamo.
“There is a significant increase in annual temperature sums. Trees start to blossom at the end of May or the beginning of June, whereas previously you would have been lucky to make a proper sauna whisk by midsummer,” says A. Polojärvi.
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Finnish forests are growing well
Jari Hynynen disagrees with those who claim that carbon sequestration is highest in unmanaged forests, explaining that the majority of Finland's forests are healthy and in a good growth phase. “Carbon stocks would undoubtedly increase if logging were stopped for the next ten years, but over time (in the long term) this would not be a very sustainable way of managing the forest in terms of carbon sequestration,” says J. Hynynen.
J. Hynynen explains: if logging were stopped in Finland, forests would gradually age and become denser; they would lose their vitality and the risk of damage would increase. At the same time, carbon sequestration would decrease and soon reach zero, meaning the forest would reach a state of equilibrium.
“The net increase in carbon sequestration and biomass would be zero. All the accumulated carbon would be lost somewhere else. The forest would form a huge carbon store, but it would no longer absorb carbon from the atmosphere,” points out Jari Hynynen.
It would take several centuries to reach equilibrium
“It would be a very long process, but in a very fertile site it would take less time. Theoretically, we would move in that direction if we stopped doing anything,” says J. Hynynen. In J. Hynynen's view, the best carbon sequestration is provided by a forest with healthy and viable trees.
“In such a case, carbon storage is reasonable and new carbon is sequestered. We know that, ultimately, what matters most is how much timber we remove from the forest and what we make from that timber,” says J. Hynynen.
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