Post E, Forchhammer M C
Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
BMC Ecol. 2001;1:5. doi: 10.1186/1472-6785-1-5. Epub 2001 Dec 6.
Large-scale climatic variability has been implicated in the population dynamics of many vertebrates throughout the Northern Hemisphere, but has not been demonstrated to directly influence dynamics at multiple trophic levels of any single system. Using data from Isle Royale, USA, comprising time series on the long-term dynamics at three trophic levels (wolves, moose, and balsam fir), we analyzed the relative contributions of density dependence, inter-specific interactions, and climate to the dynamics of each level of the community.
Despite differences in dynamic complexity among the predator, herbivore, and vegetation levels, large-scale climatic variability influenced dynamics directly at all three levels. The strength of the climatic influence on dynamics was, however, strongest at the top and bottom trophic levels, where density dependence was weakest.
Because of the conflicting influences of environmental variability and intrinsic processes on population stability, a direct influence of climate on the dynamics at all three levels suggests that climate change may alter stability of this community. Theoretical considerations suggest that if it does, such alteration is most likely to result from changes in stability at the top or bottom trophic levels, where the influence of climate was strongest.
大规模气候变率与北半球许多脊椎动物的种群动态有关，但尚未证明其直接影响任何单一系统多个营养级的动态。利用美国皇家岛的数据，这些数据包括三个营养级（狼、驼鹿和香脂冷杉）长期动态的时间序列，我们分析了密度依赖、种间相互作用和气候对群落各营养级动态的相对贡献。
尽管捕食者、食草动物和植被营养级的动态复杂性存在差异，但大规模气候变率直接影响了所有三个营养级的动态。然而，气候对动态的影响强度在顶部和底部营养级最强，而密度依赖在这些营养级最弱。
由于环境变率和内在过程对种群稳定性的影响相互冲突，气候对所有三个营养级动态的直接影响表明气候变化可能改变该群落的稳定性。理论思考表明，如果确实如此，这种改变最有可能是由顶部或底部营养级稳定性的变化导致的，而气候在这些营养级的影响最强。
