Which rotation length is favourable to carbon sequestration?

Regulating the rotation length of tree stands is an effective way to manage the carbon budget of forests. We analyzed, using models, how a 30-year change in rotation length from the recommended 90 years would change the carbon and energy budgets of typical wood-production and wood-use chains in Finland. Shortening the rotation length towards the culmination age of mean annual increment decreased the carbon stock of trees but increased the carbon stock of soil, because the production of litter and harvest residues increased. Changes in the carbon stock of wood products varied with tree species depending on volumes and timber sorts harvested, manufacturing processes and products manufactured. The Scots pine (Pinus sylvestris L.) chain stored the largest total amount of carbon when applying the longest rotation length and the Norway spruce (Picea abies (L.) Karst.) chain, when applying the shortest rotation length. Fossil carbon emissions and energy use in harvesting and manufacture increased when the rotation length was shortened and pulpwood harvests increased, especially in the spruce chain. We concluded that longer rotation length at the sites of both tree species would be favourable to carbon sequestration. The costs of this would be decreased timber harvests and decreased revenues of landowners. Our results demonstrate the importance of accounting for the whole wood-production and wood-use chain, including fossil carbon emissions, when analysing the effects of rotation length on forest carbon sequestration.