The addition of biochar to soil may offer a chance to mitigate climate change by increasing soil carbon stocks, improving soil fertility and enhancing plant growth. The impacts of biochar in cold environments with limited microbial activity are still poorly known.

Drainage is an essential prerequisite in peatland forest management, which generally, but not always, increases stand growth. Growth response depends on weather conditions, stand and site characteristics, management and biogeochemical processes. We constructed a SUSI-simulator (SUoSImulaattori, in Finnish), which describes hydrology, stand growth and nutrient availability under different management, site types and weather conditions. In the model development and sensitivity analysis, we used water table ($WT$) and stand growth data from 11 Scots pine stands. The simulator was validated against a larger dataset collected from boreal drained peatlands in Finland. In validation, SUSI was shown to predict $WT$ and stand growth well. Stand growth was mainly limited by inadequate potassium supply, and in Sphagnum peats by low oxygen availability. Model application was demonstrated for ditch network maintenance (DNM) by comparing stand growth with shallow (−0.3 m) and deep ditches (−0.9 m): The growth responses varied between 0.5 and 3.5 m³ ha⁻¹ in five years, which is comparable to experimental results. SUSI can promote sustainable peatland management and help in avoiding unnecessary drainage operations and associated environmental effects, such as increased carbon emissions, peat subsidence, and nutrient leaching. The source code is publicly available, and the modular structure allows model extension to cost–benefit analyses and nutrient export to water courses.

The contents of nitrogen (N) have generally been observed to increase in the early stages of decomposition in coarse woody debris and then to decrease slowly. This is potentially an important mechanism of nutrient retention in ecosystems after disturbances. We studied N dynamics in decomposing Scots pine ( Pinus sylvestris L.), Norway spruce ( Picea abies (L.) Karst.), and silver birch ( Betula pendula Roth.) stems in Finland. The oldest stems had decomposed for 34 (spruce and birch) or 45 (pine) years. Concentrations of N in both fallen logs and standing snags increased and C/N ratios decreased with time, and birch had significantly higher N concentrations and lower C/N ratios than pine and spruce. Even though increased N contents were observed in some cases, N was generally already released in the early stages of decomposition and more rapidly from birch than from conifers. Based on model analysis, from 40% (pine and spruce) to 50% (birch) of initial N was released within 30 years. The results suggest that decomposing stems of especially Scots pine and Norway spruce retain N rather effectively in boreal forest ecosystems and form a long-term, small but steady N pool with a slow release rate.