Modelling the effects of environmental conditions on wood physico-mechanical properties

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Atmospheric CO2 concentrations and nitrogen (N) deposition rates have increased substantially over the last century due to human activities and are expected to continue unabated. At the same time, forest management practices are also changing, mainly because of an increased necessity for immediate returns on investment. There is thus considerable pressure to understand and predict how tree growth, carbon storage and wood quality will be affected by changes environmental conditions and management practices in the future. Given that wood is the principal merchantable product derived from harvested forests, wood formation is arguably the most economically important process associated with perennial growth in forest trees. This research program is dedicated to developing models that can help predict and understand the within-stem distribution of wood properties, and that can be linked to tree growth simulators to predict the impact of silvicultural practices on wood product flows and value. Over the next five years, the development of our models will focus on obtaining an improved fundamental understanding of the effects of environmental factors on wood physico-mechanical properties. This will be achieved by pursuing three specific objectives: 1) to investigate the effects of climate and the potential interaction with elevated CO2 on wood properties 2) to understand the effects of changes in site characteristics and stand dynamics after major disturbances, such as fires or clearcut, and 3) to test the impact of biomechanical stimuli on the between-tree variation in wood mechanical properties. Wood samples from contrasted growing environments will be used to study the inter-relationships between forest disturbance, tree growth, wood properties, climate and atmospheric conditions. The key species that will be studied are black spruce (Picea mariana) from the boreal forest of Quebec where growth is temperature-limited and 2) loblolly pine (Pinus taeda) trees from the FACE experiment at Duke University in North Carolina exposed to enriched CO2 levels (+200 PPM) for 15 years and Nitrogen fertilisation for 5 years. The radial patterns of variation of different wood properties, such as density, mechanical stiffness and strength, chemical composition and cell dimensions, will be measured on more than 4000 wood discs. The developed models will not only provide a common platform for the integration of our most up-to-date knowledge on the long-term effects of changing environmental conditions on wood structure, they will also help inform decision-making earlier in the forest value chain, and thus improve the future efficiency of this important sector for the Canadian economy.