Nitrogen fertilisation boosts soil carbon storage in Scots pine forests
Forests play a vital role in global carbon storage, with most of this carbon held belowground. New HoliSoils research by the Natural Research Institute Finland (Luke) highlights mechanisms how nitrogen fertilisation of forest soils can enhance soil organic carbon (SOC) pools, offering a promising strategy for climate change mitigation.
The research team conducted a long-term fertilisation experiment in a Scots pine stand, combining chemistry, microbiology, and greenhouse gas flux measurements. The goal was to uncover the mechanisms behind the observed increase in soil carbon following nitrogen addition.
Nitrogen fertilisation increased carbon stocks, microbial biomass, necromass and the activity of extracellular enzymes, with no significant increase in greenhouse gas production. Moreover, nitrogen fertilisation decreased the production of a group of plant secondary metabolites, tannins. These profound changes were observed in the organic layer of the soil, and differences in the mineral soil were less detectable.
The results suggest that increased plant litter, fungal biomass and fungal necromass stabilised in the soil are the mechanisms behind the increase in the SOC pool, rather than changes in the composition of the fungal community, the suppression of decomposition of recalcitrant SOC or changes in pH.
“Our research supports the idea that nitrogen fertilisation can be used to increase microbial necromass in persistent carbon pools in forest soil. This approach could be an effective tool in forest management strategies aimed at mitigating climate change”, concludes Sylwia Adamczyk, Senior Scientist at Luke.
The research adds to growing evidence that targeted soil management practices can significantly impact carbon dynamics in forest ecosystems.
Read the full HoliSoils pubblication
This article was written by the Natural Resources Institute Finland (Luke).
More information:
Adamczyk, B., Adamczyk, S., Tupek, B., Li, Q., Martinovic, T., Richy, E., Lehtonen, A., Baldrian, P., & Mäkipää, R. (2025). Nitrogen fertilisation of boreal forest soil increases soil carbon pool through elevated microbial necromass formation but also modifies tree secondary metabolism. Soil Biology and Biochemistry, 109917. https://doi.org/10.1016/j.soilbio.2025.109917
