Model computations on sequestration of carbon in managed forests and wood products under changing climatic conditions in Finland

The aim of this study was to assess the effects of forest management on carbon sequestration in forests and wood products by using a gap-type forest model interfaced with a wood product model. The assessment is based on total carbon sequestration, i.e. the amount of carbon left in vegetation, litter, soil organic matter and products when the hows of carbon back to the atmosphere have been subtracted. Thirty mixed-species stands, representing medium fertility sites in southern Finland, were included in each simulation for 300 years under current climatic conditions and predicted conditions of changing climate. The average total balance for the first 100 years was higher in the unmanaged system than in the managed system, but for the second and third 100-year periods the results were clearly opposite. Differences in the total balance between the treatments were larger during the first 100 years than over the whole 300-year period. Under conditions of changing climate, differences in carbon sequestration between management options were more pronounced than under current climatic conditions. Under current climatic conditions with the 100-year time frame, the ratio between the total annual balance and annual gross production was 0.208-0.289. Over the whole 300 years, however, efficiency was much lower, 0.088-0.121. Under changing climatic conditions, efficiency was also lower, 0.182-0.252 and 0.081-0.096, respectively. Different management alternatives clearly produced different amounts of timber for the production process; under conditions of changing climate, timber production was substantially enhanced. However, total carbon storages at the end of the simulation varied less than timber production. In the managed system, the how back into the atmosphere was largest from litter, 41-51% of the total outflow, the how from vegetation was 23-28%, from soil organic matter 22-25%, emissions from products 1-7%, and emissions from landfills 0-3%. If emissions due to the use of machinery in timber harvesting and transportation were included, they made up only 0.03-0.33% of the total outflow. (C) 1996 Academic Press Limited