Soil GHG dynamics after water level rise - Impacts of selection harvesting in peatland forests

Mikko Peltoniemi; Qian Li; Pauliina Turunen; Boris Tupek; Päivi Mäkiranta; Kersti Leppä; Mitro Müller; Antti J Rissanen; Raija Laiho; Jani Anttila; Jyrki Jauhiainen; Markku Koskinen; Aleksi Lehtonen; Paavo Ojanen; Mari Pihlatie; Sakari Sarkkola; Elisa Vainio; Raisa Mäkipää

doi:10.1016/j.scitotenv.2023.165421

Soil GHG dynamics after water level rise - Impacts of selection harvesting in peatland forests

Sci Total Environ. 2023 Nov 25:901:165421. doi: 10.1016/j.scitotenv.2023.165421. Epub 2023 Jul 18.

Authors

Mikko Peltoniemi¹, Qian Li², Pauliina Turunen³, Boris Tupek², Päivi Mäkiranta², Kersti Leppä², Mitro Müller², Antti J Rissanen⁴, Raija Laiho², Jani Anttila², Jyrki Jauhiainen², Markku Koskinen⁵, Aleksi Lehtonen², Paavo Ojanen², Mari Pihlatie⁵, Sakari Sarkkola², Elisa Vainio⁵, Raisa Mäkipää²

Affiliations

¹ Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland. Electronic address: mikko.peltoniemi@luke.fi.
² Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland.
³ Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland; Environmental Soil Science, Department of Agricultural Sciences, University of Helsinki, Viikinkaari 9, 00790 Helsinki, Finland.
⁴ Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland; Faculty of Engineering and Natural Sciences, Bio and Circular Economy research group, Tampere University, Korkeakoulunkatu 8, 33720 Tampere, Finland.
⁵ Environmental Soil Science, Department of Agricultural Sciences, University of Helsinki, Viikinkaari 9, 00790 Helsinki, Finland.

PMID: 37474057
DOI: 10.1016/j.scitotenv.2023.165421

Abstract

Managed boreal peatlands are widespread and economically important, but they are a large source of greenhouse gases (GHGs). Peatland GHG emissions are related to soil water-table level (WT), which controls the vertical distribution of aerobic and anaerobic processes and, consequently, sinks and sources of GHGs in soils. On forested peatlands, selection harvesting reduces stand evapotranspiration and it has been suggested that the resulting WT rise decreases soil net emissions, while the tree growth is maintained. We monitored soil concentrations of CO₂, CH₄, N₂O and O₂ by depth down to 80 cm, and CO₂ and CH₄ fluxes from soil in two nutrient-rich Norway spruce dominated peatlands in Southern Finland to examine the responses of soil GHG dynamics to WT rise. Selection harvesting raised WT by 14 cm on both sites, on average, mean WTs of the monitoring period being 73 cm for unharvested control and 59 cm for selection harvest. All soil gas concentrations were associated with proximity to WT. Both CH₄ and CO₂ showed remarkable vertical concentration gradients, with high values in the deepest layer, likely due to slow gas transfer in wet peat. CH₄ was efficiently consumed in peat layers near and above WT where it reached sub-atmospheric concentrations, indicating sustained oxidation of CH₄ from both atmospheric and deeper soil origins also after harvesting. Based on soil gas concentration data, surface peat (top 25/30 cm layer) contributed most to the soil-atmosphere CO₂ fluxes and harvesting slightly increased the CO₂ source in deeper soil (below 45/50 cm), which could explain the small CO₂ flux differences between treatments. N₂O production occurred above WT, and it was unaffected by harvesting. Overall, the WT rise obtained with selection harvesting was not sufficient to reduce soil GHG emissions, but additional hydrological regulation would have been needed.

Keywords: Climate smart forestry; Continuous cover forestry; Gradient method; Norway spruce mire; Peatland hydrology; Soil greenhouse gas emissions.