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

• Published in: Biogeosciences
• Main Authors: Alm, Jukka, Wall, Antti, Myllykangas, Jukka-Pekka, Ojanen, Paavo, Heikkinen, Juha, Henttonen, Helena M., Laiho, Raija, Minkkinen, Kari, Tuomainen, Tarja, Mikola, Juha
• Format: Text
• Language: English
• Published: 2023
• Subjects: Northern Finland
• Online Access: https://doi.org/10.5194/bg-20-3827-2023; https://bg.copernicus.org/articles/20/3827/2023/

In peatlands drained for forestry, the soil carbon (C) or carbon dioxide (CO 2 ) balance is affected by both (i) higher heterotrophic CO 2 -C release from faster decomposing soil organic matter (SOM) and (ii) higher plant litter C input from more vigorously growing forests. This balance and other greenhouse gas (GHG) sinks and sources in managed lands are annually reported by national GHG inventories to the United Nations Climate Change Convention. In this paper, we present a revised, fully dynamic method for reporting the CO 2 balance of drained peatland forest soils in Finland. Our method can follow temporal changes in tree biomass growth, tree harvesting and climatic parameters, and it is built on empirical regression models of SOM decomposition and litter input in drained peatland forests. All major components of aboveground and belowground litter input from ground vegetation as well as live trees and trees that died naturally are included, supplemented by newly acquired turnover rates of woody plant fine roots. Annual litter input from harvesting residues is calculated using national statistics of logging and energy use of trees. Leaching, which also exports dissolved C from drained peatlands, is not included. The results are reported as time series from 1990–2021 following the practice in the GHG inventory. Our revised method produces an increasing trend of annual emissions from 0.2 to 2.1 t CO 2 ha −1 yr −1 for the period 1990–2021 in Finland (equal to a trend from 1.4 to 7.9 Mt CO 2 yr −1 for the entire 4.3 Mha of drained peatland forests), with a statistically significant difference between the years 1990 and 2021. Across the period 1990–2021, annual emissions are on average 1.5 t CO 2 ha −1 yr −1 (3.4 Mt CO 2 yr −1 for 2.2 Mha area) in warmer southern Finland and − 0.14 t CO 2 ha −1 yr −1 ( − 0.3 Mt CO 2 yr −1 for 2.1 Mha area) in cooler northern Finland. When combined with data on the CO 2 sink created by the growing tree stock, in 2021 the drained peatland forest ecosystems were a source of 1.0 t CO ...