Change in soil organic carbon content in European mountain forests based on LUCAS soil databases 2009-2018

Forest ecosystems act as huge reservoirs of organic carbon by binding atmospheric carbon dioxide in the process of photosynthesis. Carbon in forests is stored both in aboveground and belowground biomass as well as in the form of dead organic matter in the soil. This soil organic carbon (SOC) pool may play a particularly important role in mitigating climate change through the long-lasting retention of organic compounds.

Much of Europe's forests are located in the mountains, where low temperatures and high humidity protect dead organic matter from rapid oxidation. In addition, the area covered by forests is increasing due to forest succession in abandoned areas. Both land cover change, as well as tree species conversion, are the factors that can lead to significant changes in SOC content. Thus, the aim of this study was to determine the impact of land use, land-use change, and forestry (LULUCF) on SOC content in European mountain forest ecosystems.

Data on land cover and SOC content in European mountains (areas above 500 m a.s.l.) were obtained from the 2009, 2015 and 2018 Land Use and Coverage Area frame Survey (LUCAS) databases. We compared the SOC content of sites that were under forests in 2009 or 2018, with or without changes in land use or species composition over the designated period. The highest increase in SOC content was noted at sites where conversion from meadow to deciduous forest took place (mean 3.46 g C kg^-1 year^-1). The SOC content decreased at sites that in the period 2009-2018 were constantly under mixed forests (mean -0.87 g C kg^-1 year^-1) and under coniferous forests (mean -0.21 g C kg^-1 y^-1), while at sites located under deciduous forests, the SOC content increased (mean 1.08 g C kg^-1 y^-1). These results suggest that forestation and maintenance of deciduous forests may have the greatest impact on carbon sequestration in mountain ecosystems in Europe.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952327 (HES-GEO).