Carbon stock changes of forest land in Finland under different levels of wood use and climate change.

Context: Prediction of the effect of harvests and climate change (CC) on the changes in carbon stock of forests is necessary both for CC mitigation and adaptation purposes. Aims: We assessed the impact of roundwood and fuelwood removals and climate change (CC) on the changes in carbon stock of Finnish forests during 2007-2042. We considered three harvest scenarios: two based on the recent projections of roundwood and fuelwood demand, and the third reflecting the maximum sustainable cutting level. We applied two climate scenarios: the climate was in the state that prevailed around year 2006, or it changed according to the IPCC SRES A1B scenario. Methods: We combined the large-scale forestry model MELA with the soil carbon model Yasso07 for mineral soils. For soils of drained, forested peatlands, we used a method based on emission factors. Results: The stock change of trees accounted for approximately 80 % of the total stock change. Trees and mineral soils acted as carbon sinks and the drained peatland soils as a carbon source. The forest carbon sink increased clearly in both of the demand-based scenarios, reaching the level of 13-20 Tg C/year (without CC). The planned increase in the use of bioenergy reduced the forest sink by 2.6 Tg C/year. CC increased the forest carbon sink in 2042 by 38 %-58 % depending on the scenario. CC decreased the sink of mineral soils in the initial years of the simulations; after 2030, the effect was slightly positive. CC increased the emissions from the drained peatland soils. Conclusions: It is likely that forest land in Finland acts as a carbon sink in the future. The changes in carbon stocks of trees, mineral soils, and peatland soils respond differently to CC and fuelwood and roundwood harvests. [ABSTRACT FROM AUTHOR]