Forest management to increase carbon sequestration in boreal Pinus sylvestris forests

Background and aims Forest management towards increased carbon (C) sequestration has repeatedly been suggested as a natural climate solution. We evaluated the potential of altered management to increase C sequestration in boreal Pinus sylvestris forest plantations. Methods At 29 forest sites, distributed along a 1300 km latitudinal gradient in Sweden, we studied interactive effects of fertilization and thinning on accumulation of C in standing biomass and the organic horizon over a 40 year period. Results Abstention from thinning increased the total C stock by 50% on average. The increase was significant (14% on average) even when C in the removed timber was included in the total ecosystem C pool. Fertilization of thinned stands increased stocks similarly regardless of including (11%) or excluding (12%) removed biomass, and fertilization combined with abstention from thinning had a synergistic effect on C stocks that generated an increase of 79% (35% when removed timber was included in the C stock). A positive effect of fertilization on C stocks was observed along the entire gradient but was greater in relative terms at high latitudes. Fertilization also reduced soil respiration rates. Conclusion Taken together, our results suggest that changed forest management practices have major potential to increase the C sink of boreal forests. Although promising, these benefits should be evaluated against the undesired effects that such management can have on economic revenue, timber quality, biodiversity and delivery of other ecosystem services.

Automated summary

The study found that in boreal Pinus sylvestris forest plantations, abstention from thinning can significantly increase carbon (C) stock, while fertilization combined with abstention from thinning further increases C stock and reduces soil respiration rates. Although promising in increasing the C sink of forests, changed forest management practices may have undesired effects on economic revenue, timber quality, biodiversity, and delivery of other ecosystem services.