Impacts of thinning and fertilization on timber and energy wood production in Norway spruce and Scots pine: scenario analyses based on ecosystem model simulations

Abstract

Based on model simulations, we studied the sensitivity of the production of energy biomass and timber to varying pre-commercial stand densities. Additionally, we studied their sensitivity to varying thinning regimes alone or combined with nitrogen fertilization. The net present value (NPV) was used to identify the cost-efficiency of management regimes. The simulations were done for Norway spruce grown on fertile (OMT) and medium fertile (MT) sites and Scots pine grown on medium fertile and poor (VT) sites in Finland. For Norway spruce, the modelled stem wood production was the highest when the pre-commercial stand was very dense and late energy wood thinning was modelled together with fertilization. For Scots pine grown on the MT site, the response was similar to Norway spruce. However, on the VT site, the modelled stem wood production was the highest, when the pre-commercial stand was moderately dense and early energy wood thinning was modelled with fertilization. NPV was the highest when the pre-commercial stand was very dense, providing early income. However, energy wood price of 3–11 € m3 would be needed to make the integration of timber and energy wood production more profitable than that aiming for timber production alone without any subsidies.