Crown Architecture, Wood Stiffness and the Pipe Model Theory for White Spruce [Picea glauca (Moench) Voss] and Aspen (Populus tremuloides Michx.) by Derek Felix Sattler A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Forest Biology & Management Department of Renewable Resources University of Alberta © Derek Felix Sattler, 2015 Abstract 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 “neighbourhood” conditions. An ii 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. iii Preface This thesis is my original work. I was responsible for the sampling design and either completed or oversaw the collection of all measurements used in this thesis. I completed all the analyses and authored all the written text presented in this thesis. The contributions I received from my supervisor (Dr. Philip G Comeau) were in the form of comments and edits to drafts of chapters 2, 3 and 4 of this thesis. Comments and edits to drafts of chapters 2 and 3 were also provided by Dr. Alexis Achim. The final structure of the chapters 2, 3 and 4 were also shaped by the comments from anonymous reviewers received during the peer-review process when the articles were submitted to scientific journals for publication. A version of chapter 2 has been published as: Sattler, D.F., Comeau, P. G., and Achim, A. 2014. Within-tree patterns of wood stiffness for white spruce (Picea glauca) and trembling aspen (Populus tremuloides). Canadian Journal of Forest Research 44: 162–171. dx.doi.org/10.1139/cjfr-2013-0150 A version of chapter 3 has been published as: Sattler, D.F., Comeau, P. G., and Achim, A. 2014. Branch models for white spruce (Picea glauca (Moench) Voss) in naturally regenerated stands. Forest Ecology and Management 325: 74–89. doi:10.1016/j.foreco.2014.03.051 A version of chapter 4 has been accepted for publication: Sattler, D.F., and Comeau, P.G. (In press). Crown allometry and application of the Pipe Model Theory to white spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.). Canadian Journal of Forest Research. iv Data collected for this thesis (presented in chapters 2 and 3) and text describing the sampling methods were used in following publication of which I am a co-author: Power, H., LeMay, V., Berninger, F., Sattler, D. and Kneeshaw, D. 2012. Differences in crown characteristics between black (Picea mariana) and white spruce (Picea glauca). Canadian Journal of Forest Research 42: 1733-1743. 10.1139/x2012-106 v Acknowledgements I would like to thank my supervisor, Dr. Philip G. Comeau as well as my co-supervisor Dr. Alexis Achim. Thank you for your suggestions, comments, support and patience. I am also grateful for the advice provided by the members of my thesis committee. The work presented in this paper was completed while I was a member of the Forest Value Network / Projet Forêt Valeur, which was a formed through a strategic network grant from Natural Sciences and Engineering Research Council of Canada (NSERC). I wish to gratefully acknowledge the NSERC and those responsible for the original network proposal submitted to NSERC. The exchange of ideas with others in this network was instrumental in how this thesis evolved into its present form. I wish to offer an enormous “thanks!” to the numerous field and lab assistants who contributed to the collection of data used in the analyses. I wish to thank the staff at Centre de research sur les matériaux renouvelables at Université Laval, Québec, where a significant portion of the work within this thesis was completed. En fin. Rut, on l’a réussi. Quelle expérience. J’ai tellement hâte à vivre tous les défis qui viendront. Es mi Guapa! vi Table of Contents Abstract ........................................................................................................................................... i Preface ........................................................................................................................................... iv Acknowledgements ...................................................................................................................... vi Table of Contents ........................................................................................................................ vii List of Tables ............................................................................................................................... xii List of Figures ............................................................................................................................. xvi Chapter 1: Introduction ................................................................................................................1 1.1 Why this study was completed ....................................................................................... 1 1.2 Thesis objectives ............................................................................................................. 6 1.3 White spruce, aspen and the importance of a baseline ................................................... 7 1.4 Wood stiffness and its components............................................................................... 11 1.5 Wood stiffness and tree function .................................................................................. 13 1.6 Branching characteristics and wood quality ................................................................. 15 1.7 Crobas and the pipe model theory ................................................................................ 17 References .....................................................................................................................................20 Chapter 2: Within-tree patterns of wood stiffness for white spruce (Picea glauca [Moench] Voss) and trembling aspen (Populus tremuloides Michx.) ........................................................29 vii 2.1 Introduction ................................................................................................................... 29 2.2 Material and methods .................................................................................................... 32 2.2.1 Site description and sample preparation ................................................................... 32 2.2.2 Covariates for analyses ............................................................................................. 37 2.2.3 Model screening ........................................................................................................ 39 2.2.4 Cambial age or tree size? .......................................................................................... 40 2.2.5 Models for pith to bark wood stiffness ..................................................................... 42 2.3 Results ........................................................................................................................... 43 2.3.1 Cambial age or tree size? .......................................................................................... 43 2.3.2 Final mixed effect models ......................................................................................... 44 2.4 Discussion ..................................................................................................................... 50 2.4.1 Cambial age or tree size? .......................................................................................... 50 2.4.2 Final models for pith to bark wood stiffness ............................................................ 52 2.5 Conclusions ................................................................................................................... 55 References .....................................................................................................................................56 Chapter 3: Branch models for white spruce (Picea glauca (Moench) Voss) in naturally regenerated stands .......................................................................................................................62 3.1 Introduction ................................................................................................................... 62 3.2 Material and methods .................................................................................................... 66 viii 3.2.1 Site description and measurements ........................................................................... 66 3.2.2 Model building .......................................................................................................... 69 3.3 Results ........................................................................................................................... 74 3.3.1 Number of branches per stem section ....................................................................... 74 3.3.2 Diameter of the largest branch per stem section ....................................................... 81 3.3.3 Diameter of branches smaller than the largest .......................................................... 85 3.3.4 Branch angle ............................................................................................................. 88 3.4 Discussion ..................................................................................................................... 93 3.4.1 Number of branches per section ............................................................................... 93 3.4.2 Diameter of the largest branch per section ............................................................... 96 3.4.3 Branch diameter other than the largest branch ......................................................... 97 3.4.4 Branch angle ............................................................................................................. 97 3.4.5 Model applications and conclusions ......................................................................... 98 References ...................................................................................................................................101 Chapter 4: Crown allometry and application of the Pipe Model Theory to white spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.)...............................107 4.1 Introduction ................................................................................................................. 107 4.2 Material and methods .................................................................................................. 110 4.2.1 Site description........................................................................................................ 110 ix 4.2.2 Field and laboratory measurements ........................................................................ 111 4.2.3 Scaling up from branch to tree ................................................................................ 112 4.2.4 Whole crown allometry........................................................................................... 114 4.2.5 Within-crown allometry .......................................................................................... 114 4.2.6 Whole-crown foliage mass from pipe model theory............................................... 115 4.2.7 Within-crown foliage mass from pipe model theory .............................................. 116 4.3 Results ......................................................................................................................... 117 4.3.1 Foliage mass and crown length: whole crown allometry ........................................ 117 4.3.2 Foliage mass and crown length: within-crown allometry ....................................... 119 4.3.3 Pipe model ratio: whole-crown allometry............................................................... 123 4.3.4 Pipe model ratio: within-crown allometry .............................................................. 125 4.4 Discussion ................................................................................................................... 129 4.4.1 Foliage mass – crown length allometry .................................................................. 129 4.4.2 Within-crown scaling between foliage mass and crown length .............................. 132 4.4.3 Whole crown foliage mass from pipe model theory ............................................... 133 4.4.4 Within-crown foliage mass from pipe model theory .............................................. 135 4.5 Conclusions ................................................................................................................. 138 References ...................................................................................................................................139 x