Crown-fibre attribute relationships for enhanced forest inventory: Progress and prospects

A five-year project, Crown-Fibre Attribute Relationships (CFAR), was completed by the Canadian Wood Fibre Centre (Natural Resources Canada) to explore the relationships between tree crown characteristics and wood fibre attributes. The CFAR project used a number of data sets distributed across Canada (e.g., silvicultural experiments), providing a range of crown conditions following spacing and thinning treatments. The approaches developed under the CFAR project, along with other relevant research, indicate that is possible to enhance current forest inventories by providing estimates of fibre attributes from crown characteristics of individual trees that can, or are poised to be, captured using remotely sensed data. Predictability was related to the dimensionality of the fibre attributes with models for zero-dimensionality fibre attributes (e.g., DBH) showing RMSE of 10% to 15% of mean values. Also, one-dimensional (e.g., sapwood area) and two-dimensional (i.e., ring area) models quantified longitudinal patterns with low bias. Current values of wood density were not related to crown characteristics; instead, recent research suggests that wood density is regulated by hydraulic and biomechanical constraints. Further evolution of remote sensing technology and related research will help to address the temporal problem posed by two- and three-dimensional fibre attributes.