how stand productivity results from size- and competition-dependent growth and mortality如何站在生产力大小的结果u2014u2014和competition-dependent增长和死亡率.pdfVIP

How Stand Productivity Results from Size- and Competition-Dependent Growth and Mortality 1 2 3 2 John P. Caspersen *, Mark C. Vanderwel , William G. Cole , Drew W. Purves 1 Faculty of Forestry, University of Toronto, Toronto, Canada, 2 Computational Ecology and Environmental Science Group, Microsoft Research, Cambridge, United Kingdom, 3 Ontario Forest Research Institute, Sault Ste. Marie, Canada Abstract Background: A better understanding of the relationship between stand structure and productivity is required for the development of: a) scalable models that can accurately predict growth and yield dynamics for the world’s forests; and b) stand management regimes that maximize wood and/or timber yield, while maintaining structural and species diversity. Methods: We develop a cohort-based canopy competition model (‘‘CAIN’’), parameterized with inventory data from Ontario, Canada, to examine the relationship between stand structure and productivity. Tree growth, mortality and recruitment are quantified as functions of diameter and asymmetric competition, using a competition index (CAIh) defined as the total projected area of tree crowns at a given tree’s mid-crown height. Stand growth, mortality, and yield are simulated for inventoried stands, and also for hypothetical stands differing in total volume and tree size distribution. Results: For a given diameter, tree growth decreases as CAIh increases, whereas the probability of mortality increases. For a given CAIh, diameter growth exhibits a humped pattern with respect to diameter, whereas mortality exhibits a U-shaped pattern reflecting senescence of large trees. For a fixed size distribution,