TimberTracer: A Comprehensive Framework for the Evaluation of Carbon Sequestration by Forest Management and Substitution of Harvested Wood Products.

Carbon storage in harvested wood products (HWPs) and the associated substitution effects resulting from their utilization over fossil fuels and energy-intensive materials are pivotal strategies in climate change mitigation. Recognition of this nature-based solution as integral to climate change mitigation targets is notably solidified in many Nationally Determined Contributions (NDCs) submitted by Parties under the Paris agreement. The need to integrate greenhouse gas (GHG) emissions and removals from HWPs in the accounting obligations under the Paris Agreement, along with the necessity to guide decision-making in forest management to optimize the climate change mitigation effect across the entire forest sector, necessitates typical decision-oriented tools known as carbon accounting models. Among these, wood products models (WPMs), that are specifically dedicated to projecting carbon in HWPs and potentially estimating the substitution effect. In this paper, we propose a novel, comprehensive framework called "TimberTracer" designed to explicitly simulating carbon stock in HWPs over temporal scales, substitution effects, and carbon emissions from wood decay and bioenergy. Furthermore, this model can be coupled with forest dynamics models to simulate the long-term effects and interaction between forest management and wood-use scenarios. The model, coupled with the 3D-CMCC-FEM growth model, was applied to the Laricio Pine (Pinus nigra subsp. laricio) situated in the Bonis watershed in southern Italy. The aim was to dynamically assess the impact of three forest management practices (clearcut, selective thinning, and shelterwood) and four wood-use scenarios (business as usual, increased recycling rate, extended average lifespan, and a simultaneous increase in both the recycling rate and the average lifespan), throughout ~140-year planning horizon (1958-2095), on the overall carbon balance. This investigation, covering HWPs stock, C emissions, and the substitution effect, revealed that selective thinning emerged as the optimal forest management scenario. Additionally, the simultaneous increase in both the recycling rate and the half-life time proved to be the optimal wood-use scenario.