The European Misson Soil Week takes place on 12-13 November 2024 in Brussels. These two days will feature keynote speeches, the presentation of the first Mission Soil Living Labs, engaging discussions, networking activities, and field visits. One of the Luke-led projects, HoliSoils, has been invited to participate in the discussion of its achieved results.

Aleksi Lehtonen, Research Professor at Luke, will participate in a session titled “Soil Health for a Sustainable Forest-Based Bioeconomy”. This session aims to showcase innovative approaches to forest management, with particular focus on exploring the benefits, challenges, and opportunities of sustainable, climate-positive, and biodiversity-relevant soil management in forest ecosystems. The session will also identify key knowledge gaps and research needs, providing recommendations on how future efforts, including the EU Mission Soil, can facilitate sustainable forest soil management.

Key discussion points:

• How can a holistic approach to forest soil management promote sustainable practices while ensuring the provision of ecosystem services?
• How can different forest management methods be optimized to promote soil and plant health, climate change mitigation, and sustainable forest-based bioeconomy under various environmental conditions?

The HoliSoils results, published as a policy brief in 2023, indicate that forest management practices can contribute to climate change mitigation by affecting soil carbon stocks and greenhouse gas (GHG) fluxes in European forests. Here are some key points:

1. Fertilization: The application of nitrogen and wood ash fertilizers in boreal forests and peatlands can increase soil carbon stocks.
2. Tree species selection: Choosing tree species adapted to specific site and environmental conditions can lead to an increase in soil carbon accumulation through increased forest productivity and litter input.
3. Stand thinning and harvesting: The implementation of high intensity thinning and clear-cutting practices has the potential to result in soil carbon loss and increased soil GHG emissions.
4. Harvest residue management: Removing harvest residues reduces soil carbon stocks, while soil preparation may stimulate tree growth, although it may also increase soil GHG emissions.
5. Peatland hydrology management: Higher water levels induced by stand thinning and selection harvesting (CCF) can reduce GHG emissions from drained organic forest soils. Furthermore, CCF, which means avoided clearcuttings, will also reduce GHG emissions and nutrient loading to waterways in comparison to conventional rotation forestry.
6. Biodiversity management: Protecting areas with high biodiversity and carbon stocks has the potential to exert a beneficial influence on soil carbon sequestration.

Continuous Cover Forestry (CCF) is a promising alternative to conventional rotation forestry on fertile drained peatlands. By applying CCF and selective harvesting, forest manager can avoid GHG emissions that would be realized after clear-cutting, particularly those associated with N2O. Additionally, CCF has the potential to enhance water quality by reducing nutrient loading to waterways compared to clear-cutting. CCF avoids the need for maintenance ditching and soil preparation, thereby reducing soil disturbance and maintaining soil health.

In Finland, 390,000 hectares of mature, fertile drained peatlands are scheduled for imminent harvesting. Landowners will decide whether to use CCF or rotation forestry with clear-cutting.

Further potential measures to mitigate climate change in European boreal forests include:

• Ash fertilization: Increases the biomass sink of forests over the long term.
• Nitrogen fertilization: Provides immediate but short-term climate benefits.
• Longer rotation periods: Increases average biomass and soil carbon stocks.
• Afforestation: Long-term benefits, though initial soil carbon loss may occur.
• Mixed stands: Creates more diverse and resilient forests with potentially larger carbon sinks.

Forest soil management practices must be considered when evaluating and implementing forest-related climate change mitigation activities. Key knowledge gaps exist in understanding how soil carbon balances and GHG emissions, as well as soil health indicators, are affected by forest management, climate, biodiversity loss, and other environmental changes, as well as the trade-offs between them.

The efficacy of climate-smart forest management practices is dependent on site-specific conditions, including management intensity, soil type and condition, topography, vegetation composition, climatic conditions, and recovery time after management.

Long-term soil monitoring is an essential element in verifying targeted changes in soil carbon sequestration and GHG emission reductions, maintaining and improving forest soil health, and confirming the effectiveness of forest management practices in mitigating climate change.