Thinning operations and their impact on biomass production in stands of Norway spruce and Scots pine

Forests and forestry can make substantial contributions to attempts to reduce the amount of CO2 in the atmosphere. However, management regimes differ in their effects on CO2 dynamics, so this study was undertaken to assess the effects of various thinning strategies on the following variables: the amount of biofuel produced that could replace fossil fuels; mean annual increment of biomass; the standing biomass. In the present study, 50 blocks of Scots pine (Pinus sylvestris L.) and 21 of Norway spruce (Picea abies (L.) Karst.), established in young stands in Sweden between 1966 and 1984, were examined. Five different thinning regimes were considered: ‘low thinning’, ‘one heavy thinning’, ‘thinning from above’, ‘low thinning + fertilization’ and ‘unthinned’. In the spruce blocks, there was no significant difference in mean annual increment between the thinning regimes, suggesting that fertilization did not have a positive affect on the aboveground biomass. In the pine blocks, ‘low thinning + fertilization’ was the most suitable thinning regime, since it led to a significantly larger mean annual increment than the other regimes and the quantity of biofuel produced was also large. ‘Unthinned’ had the largest standing biomass for both species, which resulted in that ‘unthinned’ is preferred if the objective is to maximize the standing biomass and thereby the carbon pool.