Episodic herbivory, plant density dependence and stimulation of aboveground plant production

Herbivory is a major energy transfer within ecosystems; an open question is under what circumstances it can stimulate aboveground seasonal primary production. Despite multiple field demonstrations, past theory considered herbivory as a continuous process and found stimulation of seasonal production to be unlikely. Here we report a new theoretical model that explores the consequences of discrete herbivory events, or episodes, separated in time. We discovered that negative density (biomass) dependence of plant growth, such as might be expected from resource limitation of plant growth, favors stimulation of seasonal production by infrequent herbivory events under a wide range of herbivory intensities and maximum plant relative growth rates. Results converge to those of previous models under repeated, short-interval herbivory, which generally reduces seasonal production. Model parameters were estimated with new and previous data from the Serengeti ecosystem. Patterns of observed frequent an...植食作用是生态系统内关键的能量传递途径；当前尚存的核心科学问题为：植食作用在何种条件下可促进地上季节性初级生产力。尽管已有多项野外实证研究佐证，过往理论均将植食作用视为连续过程，并认为其促进季节性生产的可能性极低。本文提出一种全新的理论模型，用以探究时间上相互分隔的离散植食作用事件（或称植食期）所带来的生态影响。研究发现，植物生长的负密度（生物量）依赖关系——这类效应通常源于植物生长的资源限制——在广泛的植食强度与最大植物相对生长速率范围内，更倾向于通过低频植食事件推动季节性生产。当植食作用以重复、短间隔的方式发生时，模型结果与既往研究结论一致，即通常会降低季节性生产。本模型的参数通过取自塞伦盖蒂生态系统（Serengeti ecosystem）的全新与历史数据进行估算。观测到的高频……模式