Pyrogenic degradation and carbon loss in cut-over drained peatland

Modern climate change exacerbates the problem of peat fires and requires a unified methodological approach for assessing carbon losses. The study was conducted in 2024–2025 on the territory of a developed high-moor peat deposit that was affected by fires in 2011 and is located within the Kaliningrad region (South-Eastern Baltic region). The methodology combines traditional approaches of soil science (profile method) with geobotanical techniques of revealing the indicator role of woody vegetation in determining the depth of burning and precipitation of the post-pyrogenic surface. As a basis for the applied assessment of pyrogenically altered soils, the classification of the intensity of soil fires by the depth of burning of the peat layer, adopted in the field of forest pyrology, is used. Using the example of two test sites with different residual peat deposits, organic profile thickness, and local drainage features, we studied carbon losses in the cavalier strip and on peat maps. It was shown that weak fires cause pyrogenic degradation of the upper layers of peat soils, resulting in losses ranging from 5.31 to 20.2 kg C/m2. In medium-intensity fires, pyrogenic degradation affects both the upper and lower layers of the peat profile, resulting in the formation of underground combustion cavities and thermally altered peat horizons. Carbon losses increase to 24.5–36.7 kg C/m2. In the areas of strong fires, the entire peat profile, which was originally a mixed-type deposit, undergoes pyrogenic degradation with an irreversible loss of most of the horizons and a total carbon loss of 50.36–65.40 kg C/m2. The areas of strong fires are confined to the soils of the cavalier. In the spatial aspect, carbon losses are composed of the share of fire foci of different strength in the overall mosaic pattern of the post-pyrogenic surface. A dense network of open shallow channels contributes to the rapid spread of fire into the peatland along the cavalier, which ultimately leads to high area-based carbon losses due to deeper pyrogenic degradation of soils on peat maps.