Impacts of Intensive Management and Landscape Structure on Timber and Energy Wood Production and net CO2 Emissions from Energy Wood Use of Norway Spruce

The aim of this study was to analyze the effects of intensive management and forest landscape structure (in terms of age class distribution) on timber and energy wood production (m3 ha−1), net present value (NPV, € ha−1) with implications on net CO2 emissions (kg CO2 MWh−1 per energy unit) from energy wood use of Norway spruce grown on medium to fertile sites. This study employed simulations using a forest ecosystem model and the Emission Calculation Tool, considering in its analyses: timber (saw logs, pulp) and energy wood (small-sized stem wood and/or logging residuals for top part of stem, branches, and needles) from the first thinning and harvesting residuals and stumps from the final felling. At the stand level, both fertilization and high pre-commercial stand density clearly increased timber production and the amount of energy wood. Short rotation length (40 and 60 years) outputted, on average, the highest annual stem wood production (most fertile and medium fertile sites), the 60 year rotation also outputted the highest average annual net present value (NPV with interest rates of 1–4%). On the other hand, even longer rotation lengths, up to 80 and 100 years, were needed to output the lowest net CO2 emissions per year in energy wood use. At the landscape level, the largest productivity (both for timber and energy wood) was obtained using rotation lengths of 60 and 80 years with an initial forest landscape structure dominated by older mature stands (a right-skewed age-class distribution). If the rotation length was 120 years, the initial forest landscape dominated by young stands (a left-skewed age-class distribution) provided the highest productivity. However, the NPV with interest rate of 2% was, on average, the highest with a right-skewed distribution regardless of the rotation length. If the rotation length was 120 years, normal age class distribution provided, on average, the highest NPV. On the other hand, the lowest emissions (kg CO2 MWh−1a−1) were obtained with the left-skewed age-class distribution using the rotation lengths of 60 and 80 years, and with the normal age-class distribution using the rotation length of 120 years. Altogether, the management regimes integrating both timber and energy wood production and using fertilization provided, on average, the lowest emissions over all management alternatives considered.