A size-gradient hypothesis for alpine treeline ecotones

作     者：George P.MALANSON Lynn M.RESLER 

作者机构：Department of Geographical&Sustainability SciencesUniversity of IowaIowa CityIA 52242 USA Department of GeographyVirginia TechBlacksburgVA 24061 USA 

出 版 物：《Journal of Mountain Science》 (山地科学学报（英文）)

年 卷 期：2016年第13卷第7期

页      面：1154-1161页

核心收录：

学科分类：07[理学] 0713[理学-生态学] 

基　　金：based upon work while an author served at the National Science Foundation(USA) 

主　　题：Competition Ecotone Environmental gradient Plant interaction Stress gradient Facilitation 

摘      要：Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.