Transition to selection cutting management in mature Scots pine stands: Short-term effect on carbon budget

Abstract

The study demonstrates the short-term effect of transitional selection cutting on annual carbon (C) budget in mature Scots pine stands. The applied partial harvesting is considered as selection cutting for transitioning from even-aged forest management to further continuous cover forest management. As the used harvesting method is suggested to be an alternative to clear-cut (CC), then its short-term effect on annual net ecosystem production (NEP) was studied simultaneously with clear-cutting. Partial harvesting decreased the annual net primary production of the stands by 20–40 % compared to the unmanaged plots, however, the effect on annual NEP was multifaceted and related to the species composition of the understorey and the soil microclimate. In the first post-cutting year, the NEP of partially harvested stands varied from the near- C neutral (-0.2 t C ha⁻¹ yr⁻¹) status up to C sinks (0.5–1.9 t C ha⁻¹ yr⁻¹), and all studied CC areas acted as C sources, emitting 2.4–4.1 t C ha⁻¹ yr⁻¹. However, the annual soil heterotrophic respiration flux of the CC sites retained the same magnitude as in partial cutting treatments or was even smaller. The diverse trends of short-term changes in NEP in post-harvest stands indicate that the impact of initial selection cutting on the C fluxes in mature Scots pine stands was highly site specific, related mainly to complex changes in soil Rh and stand characteristics.