Data from: 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 dependence of the interaction strength between the first two trophic levels. Our results support previous empirical findings and suggest that the loss of larger predators will have greater consequences on trophic control and biomass structure in food webs than the loss of smaller predators.

营养级联（trophic cascades）指捕食者通过调控中间消费者，对基底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（即资源密度向承载能力回弹的幅度更大），但其背后的机制尚不明确，原因在于我们尚未清晰阐明营养级联强度的决定路径。本研究借助消费者-资源模型（consumer-resource models），首先证明营养级联强度存在上限，该上限由基底营养类群与其消费者之间的交互强度所决定；且随着消费者与其捕食者之间的交互强度提升，营养级联强度会趋近于此上限。随后，我们将营养级联强度以捕食者体型为变量进行显性表达，并利用两组独立参数集计算营养级联强度随捕食者体型的变化规律。两组参数集均预测，捕食者体型对营养级联强度存在正向影响，这一规律主要由前两个营养级间的交互强度的体型依赖性所驱动。我们的研究结果佐证了此前的实证发现，并表明相较于小型捕食者的消亡，大型捕食者的丢失会对食物网的营养调控与生物量结构造成更为显著的影响。