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

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Wood physico-mechanical properties are key functional traits of trees that influence both their structural resistance to mechanical stimuli and the conductivity of sap in the xylem. Developmental constraints on wood cell production, and the need for optimising both the mechanical stability of trees and their hydraulic efficiency result in distinctive radial patterns of wood properties (i.e. juvenile and mature wood) that influence end-product performance. However, the effects of environmental conditions, and their potential interactions with silvicultural treatments, on these patterns of variation remain poorly understood. The long-term motivation for this research program is to develop models that can help understand and predict the within-stem distribution of wood properties with the aim of characterizing the suitability of the current forest resource for various end-uses and anticipating the impact of environmental conditions and silvicultural practices on wood product flows and value. Based on an improved understanding of the environmental drivers of wood formation, we aim to produce a new generation of models that can predict the variation of wood properties at a scale that is relevant to forest managers. Specifically, we will aim to 1) understand the effects of forest disturbances, such as fire, and stand dynamics on wood properties; 2) quantify the response of wood properties to climatic variables, and 3) scale up predictions between the hierarchical levels of variation, from the tree-ring to forest landscapes. To achieve this, our overall approach consists of partitioning sources of variation in wood properties from the scale of the cell wall to that of trees, stands and forest landscapes. We will use an opportunistic sampling approach whereby we will examine the growth history of trees to quantify the effects of the environmental conditions to which they were exposed. We will sample trees in five regions spanning from Northern Ontario to Newfoundland, which will allow us to investigate the effects of water availability on black spruce wood properties across the North American boreal forest. Pith-to-bark models will be produced of wood properties such as density, dimensional stability, strength and stiffness, which are key determinants of xylem structure both physiologically and in terms of the suitability for end-use. The grant will be used to fund student training in a field which has a shortage of qualified personnel in Canada. With the forest sector currently shifting from commodity to value-added production, there is significant interest in using models that can predict wood quality variation at multiple scales. The models and software tools developed within this program will not only provide an identifiable locus for the integration of our most up-to-date knowledge, but they will also help inform decision-making earlier in the value chain, and thus improve the future efficiency of this important sector for the Canadian economy.