Reviews and syntheses: Greenhouse gas exchange data from drained organic forest soils – a review of current approaches and recommendations for future research

Abstract

<p><strong>Abstract.</strong> Drained organic forest soils in boreal and temperate climate zones are believed to be significant sources of the greenhouse gases (GHG) carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O), but the annual fluxes are still highly uncertain. Drained organic soils exemplify systems where many studies are still carried out with relatively small resources, several methodologies and manually operated systems, which further involve different options for the detailed design of the measurement and data analysis protocols for deriving the annual flux. It would be beneficial to set certain guidelines for how to measure and report the data, so that data from individual studies could also be used in synthesis work based on data collation and modelling. Such synthesis work is necessary for deciphering general patterns and trends related to, e.g., site types, climate, and management, and the development of corresponding emission factors, i.e., estimates of the net annual soil GHG emission/removal, which can be used in GHG inventories. Development of specific emission factors also sets prerequisites for the background or environmental data to be reported in individual studies. We argue that wide applicability greatly increases the value of individual studies. An overall objective of this paper is to support future monitoring campaigns in obtaining high-value data. We analysed peer-reviewed publications presenting CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O flux data for drained organic forest soils in boreal and temperate climate zones, focusing on data that have been used, or have the potential to be used, for estimating net annual soil GHG emission/removals. We evaluated the methods used in data collection, and identified major gaps in background/environmental data. Based on these, we formulated recommendations for future research.

A High-Resolution Digital Elevation Model in Combination With Water Table Depth and Continuous Soil Redox Potential Measurements Explain Soil Respiration and Soil Carbon Stocks at the ICOS Site Sorø

“…When the soil was anaerobic and C-rich, fast C mineralisation due to aerobic respiration did not take place below 20 cm depth, but could happen in the top 20 cm when not flooded. Jauhiainen et al (2019) reviewed the complexity of describing C balances of forest on organic soils, and stressed the importance of water table measurements to correctly asses the soil aeration status.…”

“…For reporting and correctly classifying wetland mineral soils, the vertical fluctuations in the water table should be known, but such data are rare (Jauhiainen et al, 2019). Water saturation causes temporal shifts between aerated soil in which aerobic processes prevail, and water saturated soil in which anaerobic soil environment and processes may prevail, most notably extremely slow SOC turnover.…”

“…The risk of net carbon mineralisation from SOC accumulated in wet mineral soils increases after the loss of soil water saturation (Jauhiainen et al, 2019) causing a strong increase in Eh to the aerobic domain exceeding a Eh of 400 mV (Husson, 2013).…”

Soil and forest floor carbon balance in drained and undrained hemiboreal peatland forests

“…Currently only one default IPCC EF for the whole temperate climate region is available and it does not involve any data measured in the Baltic states (Hiraishi et al, 2013a). EF is elaborated using results from 8 sites with drained soil (Hiraishi et al, 2013a) published in 5 articles (Glenn et al, 1993;Minkkinen et al, 2007;Yamulki et al, 2013;Von Arnold et al, 2005b, a) on studies representing a wide climatic gradient and different CO2 estimation methods, which further complicates the comparability of the results that have been aggregated (Jauhiainen et al, 2019(Jauhiainen et al, , 2023. A recent synthesis study evaluated whether default IPCC EF can be improved by compiling results from most recent studies.…”