Can plasticity make spatial structure irrelevant in individual-tree models?

作     者：Oscar Garcia 

作者机构：University of Northern British Columbia3333 University WayV2N 4Z9 Prince GeorgeBCCanada 

出 版 物：《Forestry Studies in China》 (中国林学（英文版）)

年 卷 期：2014年第16卷第3期

页      面：134-146页

学科分类：090704[农学-森林经理学] 0907[农学-林学] 09[农学] 

基　　金：funded through the FRBC/West Fraser Endowed Chair in Forest Growth and Yield University of Northern British Columbia 

主　　题：Growth and yield Competition Perfect plasticity approximation (PPA) siplab 

摘      要：Background： Distance-dependent individual-tree models have commonly been found to add little predictive power to that of distance-independent ones. One possible reason is plasticity, the ability of trees to lean and to alter crown and root development to better occupy available growing space. Being able to redeploy foliage （and roots） into canopy gaps and less contested areas can diminish the importance of stem ground locations. Methods： Plasticity was simulated for 3 intensively measured forest stands, to see to what extent and under what conditions the allocation of resources （e.g., light） to the individual trees depended on their ground coordinates. The data came from 50 x 60 m stem-mapped plots in natural monospecific stands of jack pine, trembling aspen and black spruce from central Canada. Explicit perfect-plasticity equations were derived for tessellation-type models. Results： Qualitatively similar simulation results were obtained under a variety of modelling assumptions. The effects of plasticity varied somewhat with stand uniformity and with assumed plasticity limits and other factors. Stand-level implications for canopy depth, distribution modelling and total productivity were examined. Conclusions： Generally, under what seem like conservative maximum plasticity constraints, spatial structure accounted for less than 10% of the variance in resource allocation. The perfect-plasticity equations approximated well the simulation results from tessellation models, but not those from models with less extreme competition asymmetry Whole-stand perfect plasticity approximations seem an attractive alternative to individual-tree models.