Carbon balance in production forestry in relation to rotation length

The choice of a rotation length is an integral part of even-aged forest management regimes. In this study, we simulated stand development and carbon pools in four even-aged stands representing the two most common tree species in Fennoscandia, Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.), growing on high-and low-productivity sites. We hypothesized that increased rotation lengths (+ 10, + 20, and + 30 years) in comparison with today's practice would increase forests' average carbon stock during a rotation cycle but decrease the average yield. The results showed that for spruce, a moderate increase in rotation length (+ 10 years) increased both average standing carbon stock and average yield. For the longer alternatives (+ 20 and + 30 years) for spruce and for all pine alternatives, prolonging rotation lengths resulted in increased average standing carbon stocks but decreased average yield, resulting in decreased carbon storage in forest products and decreased substitution effects. Decreasing the rotation lengths (-10 years) always resulted in both decreased average standing carbon stocks and decreased yields. We conclude that a moderate increase of rotation lengths may slightly increase forests' climate benefits for spruce sites, but for all other alternatives, there was a trade-off between the temporary gain of increasing carbon stocks and the permanent loss in productivity and, consequently, substitution potential.