Carbon dynamics in Danish peatlands under changing climate

Peatlands cover around 3% of the Earth's land surface and store a significant portion of the world's soil carbon, about twice as much as the world's forests combined. These unique ecosystems are characterized by waterlogged, anoxic, and typically acidic conditions that inhibit microbial decomposition, leading to carbon accumulation and playing a vital role in the global carbon cycle. Peatlands serve as large carbon sinks; however, anthropogenic disturbances, such as draining and water table lowering for agriculture, or peat extraction for fuel and horticulture substrates, can convert them into carbon sources of greenhouse gases (GHG), such as carbon dioxide (CO₂) and methane (CH₄), which have led to increasing efforts to restore peatlands as a nature-based climate solution.

Although extensive research has improved our understanding of carbon dynamics in peatlands, including restored sites, long-term assessments remain limited. Yet, these assessments are essential for capturing climate variability and its impacts. Continuous gas monitoring, combined with physicochemical and microbial analyses, is therefore essential to evaluate the effectiveness of restoration efforts in terms of carbon sequestration. At the same time, there is a remaining knowledge gap regarding the role of microbial communities in carbon sequestration and GHG emissions. Therefore, this study aims to investigate how peatland restoration practices affect microbial activity and GHG fluxes in Danish peatlands across different seasons and years.

The study areas are located in Store Åmose, a Danish nature park on Zealand that comprises diverse peatland systems protected under the Natura 2000 network. Historically, these peatlands were converted to agriculture, forestry, and other land uses. Three sites have been selected: (i) a high water-table bog restored in 2017; (ii) a low water-table bog in a naturally forested state that has not been restored; and (iii) a high water-table fen  with a diverse, undisturbed plant community. At each site, in situ GHG emissions of CO₂ and CH₄ are measured using gas flux chambers, and soil samples are collected at three depths to assess soil physicochemical properties and microbial activity.

Preliminary results indicate that peatland restoration reduces GHG fluxes (CO₂ and CH₄). Middle and deeper soil layers in restored and non-restored bogs show similar C:N ratios and bacterial biomass, with the high C:N ratios suggesting that substantial organic carbon remains stored in the peat. Meanwhile, bacterial growth in surface layers appears to be primarily influenced by climate and vegetation, whereas deeper layers are more similar across sites. Warmer and wetter periods seem to enhance both CO₂ fluxes and microbial activity, likely driven by seasonal variations in temperature and moisture.

Understanding the relationship between microbial activity and carbon fluxes is crucial for improving our knowledge of these ecosystems and developing effective management strategies to reduce emissions and restore degraded peatlands.