%0 Research article
%T Enhanced multi-objective decision support in peatland forestry using Peatland simulator SUSI
%A Niemi, Mikko T.
%A Palviainen, Marjo
%A Laurén, Annamari
%D 2026
%J Silva Fennica
%V 60
%N 2
%R doi:10.14214/sf.25025
%U https://silvafennica.fi/article/25025
%X Boreal peatland forests have been extensively drained to increase timber production, but the maintenance of shallowed ditches has been questioned due to increased greenhouse gas (GHG) emissions and negative impacts on water quality. Ditch network maintenance (DNM) lowers water table, which typically increases tree growth, but also increases rate of peat decomposition and consequently CO<sub>2</sub> emissions. Multi-objective forest planning balances between the conflicting economic gains and adverse environmental impacts. We used a process-based Peatland simulator SUSI to simulate three management scenarios for 20 forest stands, covering the variety of growing conditions in Finland. We studied how DNM with a reduced ditch depth (60 cm) and a conventional ditch depth (90 cm) affected stand growth, GHG balance, and nitrogen and phosphorus export. Over a 20-year simulation period, annual volume growth response was on average 0.8 m<sup>3</sup> ha<sup>-1</sup> when ditch depth was changed from 30 cm to 60 cm and 1.0 m<sup>3</sup> ha<sup>-1</sup> when ditch depth was changed from 30 cm to 90 cm. In southern Finland, DNM decreased stand growth in fertile sites. Soil GHG emissions increased on average by 49% and 119% in 60 cm and 90 cm ditch depths, respectively, compared to 30 cm ditch depth. The cost of reducing GHG emissions ranged from 0–22 € per ton of CO<sub>2</sub> in our study sites and scenarios. Our results support the idea that omitting DNM or reducing ditch depth may lead to acceptable compromises, as the marginal cost of soil GHG emissions considerably increases with increasing ditch depth.