Article image: Undrained spruce swamp growing dense tree stand and bilberry on the top of one meter peat in Southern Finland. Photo credit: Hannu Nousiainen.
Finland is a country of not only forests but also peatlands. In fact, Finland has approximately 9 million hectares of peatlands, covering about almost a third of the total land area.
Peatlands play an important role in mitigating global warming: their store is about 500 gigatons of carbon (C), which is equivalent to more than half of the current atmospheric carbon. About half of the peatland area is still undrained; area types varying from treeless to tree-covered peatlands and from nutrient-rich to nutrient-poor peatlands.
Other half of the peatlands (4.95 million hectares) have been drained for forestry. Those forests cover nearly 25% of forest area in Finland. In 2021, the drained peatland forests were still an overall net sink of 0.2 Mt CO2 due to the increasing carbon stock of trees and the northern soils that sequester more carbon than they release to the atmosphere on an annual basis. (Alm et al. 2023)
Forests are major source of both economic and social wellbeing for Finland. Therefore, there has been great interest for drainage of peatlands for forestry from 1950’s to 1970’s. In ALFAwetlands project Natural Resources Institute Finland (Luke) has concentrated on restoration of drained peatlands, however the method used is not only ecological restoration but also methods to control ground water level of peatlands such as continuous cover forestry (CCF) regime.
Why continuous cover forestry can be seen as one of peatland restoration methods?
Traditionally forest harvesting in Finland has been conducted using an even-aged forestry with 60–100 years long stand rotation with a clear-cut at the end of rotation. Choosing CCF method for harvesting there is a great potential to decrease greenhouse gas (GHG) emissions at least in nutrient-rich peatland forests by avoiding the high GHG emissions after clear cut.
The CCF is a forest management regime without clear felling, and it always involves the maintenance of a forest cover at all times, which preserves large part of the tree C storage and C sink function after harvest operations (e.g., strip cutting, selective cutting). After the felling of individual large trees, the remaining trees accelerate their growth, as well as new trees, which grow from the undergrowth reserve. By regulating number of growing trees, it is possible to effect on water table level: in high water table level CO2 emissions decrease, but methane increase, in opposite in low ground water level CO2 emissions increase.
Therefore, CCF method enables optimizing water table level and furthermore enables mitigation of GHG emissions. Avoiding undesirably high a water level (typical in clear cut areas) reduces also export of nutrients (e.g., phosphorus) in runoff waters. Furthermore, it has been estimated that peatland restoration in nutrient-rich peatlands would support biodiversity and improve habitat suitability for red-listed peatland plant species. In CCF the need for ditch network maintenance in forest management is less frequent, which can also reduce management costs and thus benefit the forest owners.
Luke’s role as Lead Partner in ALFAwetlands project
Luke is one of the Europe’s leading research institutes that study natural resources in a multidisciplinary way. In addition of project coordinating role, Luke leads one of the scientific Working Packages. This is Work Package 5: Economic & social impacts of wetland restoration, which aims to study societal impacts of wetland restoration. Furthermore, Luke’s researchers play a central role in other ALFAwetlands’ Work Packages and act in them, for example, as task managers. Luke also coordinates the Living Labs (LL) of the project as well LL of Finland, comprising of six distinct sites. Four of these sites are situated in the Northern region of Finland, renowned for its abundance of wetlands: (Kivalo, Pikkusaarisuo, Sanginjoki (Asmonkorpi), and Siikajoki), while the remaining two, Lettosuo and Rottasniitunsuo, are in Southern Finland. The Finnish Meteorological Institute (FMI) hosts the latter site, collaborating closely with Luke as a partner in Finland.
Sources:
Alm J, Wall A, Myllykangas J-P, Ojanen P, Heikkinen J, Henttonen HM, Laiho R, Minkkinen K, Tuomainen T, Mikola J (2023) A new me thod for estimating carbon dioxide emissions from drained peatland forest soils for the greenhouse gas inventory of Finland. Biogeoscien ces 20:3827–3855. https://doi.org/10.5194/bg-20-3827-2023