Crown Architecture, Wood Stiffness and the Pipe Model Theory for White Spruce [Picea glauca (Moench) Voss] and Aspen (Populus tremuloides Michx.)

• Author / Creator

  Sattler, Derek F

• In forestry, the wood fibre supply chain describes the integration of harvesting operations, raw material transformation and end-product marketing. The forest industry may achieve an overall greater return on investment by developing a supply chain which incorporates measures of wood quality. The main goal of this thesis was to develop components of a decision support tool that may be used by forest managers to achieved wood quality based objectives for white spruce [Picea glauca (Moench)] and aspen (Populus tremuloides Michx.). The first component presented in this thesis is a model for the prediction of pith to bark wood stiffness. For both spruce and aspen, wood stiffness was found to develop in closer association with cambial age than tree size. The results carry implications concerning the role of the stem and the adaptation to mechanical and hydraulic demands. Based on variables included in the models, silvicultural activities that alter slenderness and radial growth rate in spruce are likely to have the greatest impact on wood stiffness. Conversely, there appears to be little opportunity for silvicultural activities to influence wood stiffness in aspen. The second component presented in this thesis is a set of models for the prediction of the number of branches, branch diameter and branch angle per unit crown length for spruce. Relative or absolute depth into the crown were significant variables in all the models, reflecting the influence of varying light transmittance on crown architecture. While tree-level variables such as crown length and tree slenderness featured in all the branch models, no indices of stand-level species composition or competition were found to directly influence the branch characteristics, other than tree social position. Overall, the models suggest that crown architecture is predominantly influenced by local “neighbourhood” conditions. An additional set of branch models were developed to identify the tree-level characteristics which influence the recovery of first grade select lumber from harvested trees. The practical application of these models may be achieved by integrating them into Crobas, a process-based tree growth simulator which uses principles related to functional balance and the pipe model theory. Tests concerning key assumptions of Crobas indicated that (i) there is indeed a constant allometric relationship between foliage mass and crown length for both spruce and aspen, and (ii) the constant ratio of foliage mass to sapwood area at crown base held reasonably well for spruce. The results, however, were less encouraging for aspen. Further efforts to validate Crobas are, therefore, recommended for white spruce. For aspen, modifications to the pipe model relationship should be sought before further validation exercises are performed. Since all components of this study examined data from unmanaged stands, the results provide a baseline reference point upon which to compare measurements from managed stands.

• Subjects / Keywords

  • Crown allometry
  • Pipe model
  • Sapwood
  • Modulus of Elasticity
  • Trembling aspen
  • Foliage mass
  • Wood quality
  • White spruce
  • Branch patterns

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3TH8BS8T

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.