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Substantial Mitigation Potential for Greenhouse Gases Under High Water Levels in a Cultivated Peatland in the Arctic

Junbin Zhao,C. Klütsch,Hanna Silvennoinen,Carla Stadler,David Kniha,Runar Kjær,Svein Wara,M. Mastepanov

Published 2025 in Global Change Biology

ABSTRACT

Drained cultivated peatlands are recognized as substantial global carbon emission sources, prompting the exploration of water level elevation as a mitigation strategy. However, the efficacy of raised water table level (WTL) in Arctic/subarctic regions, characterized by continuous summer daylight, low temperatures and short growing seasons, remains poorly understood. This study presents a two‐year field experiment conducted at a northernmost cultivated peatland site in Norway. We used sub‐daily CO2, CH4, and N2O fluxes measured by automatic chambers to assess the impact of WTL, fertilization, and biomass harvesting on greenhouse gas (GHG) budgets and carbon balance. Well‐drained plots acted as GHG sources as substantial as those in temperate regions. Maintaining a WTL between −0.5 and −0.25 m effectively reduces CO2 emissions, without significant CH4 and N2O emissions, and can even result in a net GHG sink. Elevated temperatures, however, were found to increase CO2 emissions, potentially attenuating the benefits of water level elevation. Notably, high WTL resulted in a greater suppression of maximum photosynthetic CO2 uptake compared to respiration, and, yet caused lower net CO2 emissions due to a low light compensation point that lengthens the net CO2 uptake periods. Furthermore, the long summer photoperiod in the Arctic also enhanced net CO2 uptake and, thus, the efficacy of CO2 mitigation. Fertilization primarily enhanced biomass production without substantially affecting CO2 or CH4 emissions. Conversely, biomass harvesting led to a significant carbon depletion, even at a high WTL, indicating a risk of land degradation. These results suggest that while elevated WTL can effectively mitigate GHG emissions from cultivated peatlands, careful management of WTL, fertilization, and harvesting is crucial to balance GHG reduction with sustained agricultural productivity and long‐term carbon storage. The observed compatibility of GHG reduction and sustained grass productivity highlights the potential for future paludiculture implementation in the Arctic.

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