The body-size dependence of trophic cascades

Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body size...

营养级联（trophic cascades）是捕食者通过调控中间消费者对资源产生的间接正向效应。体型更大的捕食者似乎能引发更强的营养级联效应（即资源密度向环境容纳量（carrying capacity）的更大幅度反弹），但这一现象的机制尚不清楚——因为我们缺乏对营养级联强度决定因素的清晰阐释。通过消费者-资源模型（consumer resource models），我们首先证明：营养级联的强度存在一个上限，该上限由基础营养级群与其消费者之间的相互作用强度决定；且随着消费者与其捕食者之间相互作用强度的增加，营养级联强度会逐渐趋近于这一上限。随后，我们将营养级联强度明确表述为捕食者体型的函数，并利用两组独立参数集（parameter sets）计算了营养级联强度与捕食者体型的依赖关系。两组参数集均预测捕食者体型对营养级联强度具有正向效应，这一效应主要由体型……