Radiative forcing of forest biomass production and use under different thinning regimes and initial age structures of a Norway spruce forest landscape

We studied how different thinning regimes and initial age structures of a Norway spruce (Picea abies (L.) Karst.) forest landscape affect the radiative forcing of forest biomass production and use. We considered the effects of forest carbon sequestration, substitution of materials and fossil fuels with forest biomass, and timber use efficiency. The initial age structures of our hypothetical forest landscapes in the middle boreal zone in Finland were young, middle-aged, and mature. Forest landscapes were thinned using either the current thinning recommendations (baseline) or maintaining 20% higher or 20% lower stocking over the 80-year study period. We employed forest ecosystem model simulations together with a life cycle assessment tool. The highest carbon sequestration was obtained by maintaining higher stocking in the landscapes. The initially middle-aged and mature age structures resulted in the strongest cooling of the climate in the first three decades of the simulation, but the highest cooling was found in the young age structure. However, radiative forcing was less sensitive to the thinning than to the substitution or timber use efficiency. Our results indicate that modeled climate impacts are affected by both initial age structure and forest management, which should be considered when generalizing the climate change mitigation potential of forests and forestry.