16 Dec 2022
16 Dec 2022
Status: this preprint is open for discussion.

A new method for estimating carbon dioxide emissions from drained peatland forest soils for the greenhouse gas inventory of Finland

Jukka Alm1, Antti Wall1, Jukka-Pekka Myllykangas2, Paavo Ojanen3, Juha Heikkinen3, Helena M. Henttonen3, Raija Laiho3, Kari Minkkinen4, Tarja Tuomainen3, and Juha Mikola3 Jukka Alm et al.
  • 1Natural Resources Institute Finland (Luke), Joensuu, Finland
  • 2Natural Resources Institute Finland (Luke), Kokkola, Finland
  • 3Natural Resources Institute Finland (Luke), Helsinki, Finland
  • 4Department of Forest Sciences, University of Helsinki, Helsinki, Finland

Abstract. Reporting the greenhouse gas (GHG) emissions from the LULUCF sector in the GHG inventory requires sound methods for estimating both the inputs and outputs of carbon (C) in managed ecosystems. Soil CO2 balance of forests consists of the CO2 released from decomposing soil organic matter (SOM) and the C entering the soil through aboveground and belowground plant litter input. Peatlands drained for forestry release soil C as CO2 because the drainage deepens the oxic peat layer prone to SOM decomposition. IPCC Guidelines provide default CO2 emission factors for different climatic zones and the defaults or locally adapted static emission factors are commonly in use in GHG inventory reporting for drained peatlands. In this paper, we describe a new dynamic method to estimate the CO2 balance of drained peatland forest soils in Finland. Contrary to static emission factors, the annual CO2 release from soil is in our method estimated using empirical regression models driven by time series of tree basal area (BA), derived from the national forest inventories in Finland, time series of air temperature and the drained peatland forest site type. Aboveground and belowground litter input is also estimated using empirical models with newly acquired turnover rates for tree fine roots and BA as a dynamic driver. All major components of litter input from ground vegetation and live, harvested and naturally died trees are included. Our method produces an increasing trend of emissions from 1.4 to 7.9 Mt CO2 for drained peatland forest soils in Finland for the period 1990–2021, with a statistically significant difference between years 1990 and 2021. Across the period 1990–2021, annual emissions are on average 3.4 Mt and −0.3 Mt in southern and northern parts of Finland, respectively. When combined with data of the CO2 sink created by trees, it appears that in 2021 drained peatland forest ecosystems were a source of 2.3 Mt CO2 in southern Finland and a sink of 2.5 Mt CO2 in northern Finland. We compare the emissions produced by the new method with those produced by the old GHGI method of Finland and discuss the strengths and vulnerabilities of our method in comparison to static emission factors.

Jukka Alm et al.

Status: open (until 12 Feb 2023)

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Jukka Alm et al.


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Short summary
In Finland peatlands cover one third of land area. Half of those, 4.3 Mha being drained for forestry, Finland reports sinks and sources of greenhouse gases in forest lands on organic soils following its UNFCCC commitment. We describe a new method for compiling soil CO2 balance that follows changes in tree volume, tree harvests and temperature. An increasing trend of emissions from 1.4 to 7.9 Mt CO2 was calculated for drained peatland forest soils in Finland for the period 1990–2021.