Forest Growth and Timber Quality: Crown Models and Simulation Methods for Sustainable Forest Management

ECOSYSTEMS CAN BE MODELED AT MANY different hierarchical levels. The phenomenon being simulated has a context represented by the next higher level of ecosystem organization, as well as driving mechanisms represented by the next lower level of ecosystem organization. In this sense, the level at which mechanisms are represented in models of tree crowns depends on the crown attributes or processes to be simulated. Crown models are reviewed and classified by their attribute resolution and the specific mechanisms driving the crown system to future states. Ecophysiological models fix carbon through photosynthesis and typically allocate this photosynthate to branches and foliage. Allometric models grow trees in height, diameter, and often crown size, retrieving structural attributes of the crown from allometric relationships between bole dimensions, branch size and location, and foliage amount. Architectural models simulate the twoor three-dimensional structure of the crown, sometimes by proliferation of individual modules comprising the crown. Intended applications of the model dictate the appropriate resolution in time and space and, therefore, the most appropriate and efficient mechanisms. Difficulties often arise when models are developed to meet more than one objective, particularly when the objectives entail several levels of organization. Editors’ note: The author elected not to provide a full paper for these proceedings because it was being submitted to a refereed journal. As with all of the keynote addresses, this presentation was designed to provide context for the related presentations that follow. In lieu of the keynote paper, the author’s slides from the presentation are reproduced on the following pages to introduce the topic for this section of the proceedings. Douglas A. Maguire (doug.maguire@oregonstate.edu) is a professor of silviculture, Forest Science Department, Oregon State University, Corvallis, OR 97331, USA. This presentation was published in: Dykstra, D.P.; Monserud, R.A., tech. eds. 2009. Forest growth and timber quality: Crown models and simulation methods for sustainable forest management. Proceedings of an international conference. Gen. Tech. Rep. PNW-GTR-791. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. pp. 1–13. FOREST GROWTH AND TIMBER QUALITY 2 Mechanistic crown models Objectives: (1) Provide a setting for the six papers of this session by looking somewhat comprehensively t d l t th t f a crown mo e s, or a e crown componen o forest simulation models (2) Suggest the aspects of crown models that best address the theme of this meeting Mechanistic crown models • The issue of mechanisms • Model types • Model objectives and context • Crown models for linking environment and silviculture to wood quantity and quality Kl d d i • u ges an pars mony What makes a crown model “mechanistic”? 1) Str ct ral elements comprising the cro n? u u w Crown length? Crown length and crown width? Forest Growth and Timber Quality: Crown Models and Simulation Methods for Sustainable Forest Management Session 1: Mechanistic Crown Models Why mechanisms should be in the eye of the beholder: Notes from the overground Doug Maguire Department of Forest Science Oregon State University FOREST GROWTH AND TIMBER QUALITY Crown length and crown width and biomass? First-order (primar ) y branches? Branches of all orders ith w detailed spatial information? Spatial structure of all branches and leaves, or all structural modules? What makes a crown model “mechanistic”? 1) Structural elements comprising crown? 2) Processes creating a given crown structure? Mechanisms