Modelling the effects of management intensification on multiple forest services: a Swedish case study

The study presents a method to evaluate the response of forest ecosystems to increased biomass extraction based on the integrated ecosystem model ForSAFE. It evaluates the effects of residue removal, intensification of thinnings and a shorter rotation period on a forest site in Southern Sweden. The evaluation includes multiple ecosystem indicators for productivity, carbon storage, wood production, water use and water quality. Such integrated assessments can contribute to identify negative or positive impacts affecting ecosystem services provided by forests. Results show that increased biomass extraction reduces the carbon stored in the forests, but at the same time reduces the loss of nitrogen and carbon through leaching. Within one rotation, residue removal affects the carbon stock in the soil, but it does not affect forest productivity and therefore tree carbon stock. Contrarily, the intensification of thinnings and shorter rotation periods reduce carbon stored in trees. In all cases, the amount of wood available for products increases, but the additional harvest from increased thinnings and earlier clear cutting does not compensate for the loss of carbon in trees. A positive consequence of removing the decomposing material from the site is the reduced amount of nutrients lost with runoff. Both leached nitrogen and dissolved organic carbon decrease with intensification. In addition, a positive effect of increased thinnings and a shorter rotation period is a reduced evapotranspiration, i.e. reduced water use. The effect on acidification differed depending on the time frame considered and the applied management scenario, due to different dominating processes regulating acidity. To avoid acidification, management intensification should include measures to prevent loss of base cations in the soil. Overall, under the studied conditions, the risk for negative effects seems to be smaller for residue extraction than for management changes including additional tree harvest.