Scavenger and herbivore functional role impairment modulates changes in plant communities following mass mortality events

Abstract

Abstract Mass mortality events (MMEs) of wildlife are increasingly frequent and may destabilize communities. MMEs provide a unique ecological context because they simultaneously produce a resource pulse that is sometimes coupled with the loss or severe impairment of functional roles such as predation or herbivory. Moreover, these effects are complicated by global declines in obligate vertebrate scavengers. We designed an experiment to measure the relative importance of bottom‐up (nutrient addition) and top‐down (impairment of obligate scavenger and herbivore functional roles) forces experienced during MMEs on the local plant community. Increasing carrion biomass shifted local plant assemblages from the original state promoting plants more resistant to soil disturbance (i.e. annual plants), but this effect was unique to carrion as the same amount of macronutrients entering the system did not affect the plant community. This may indicate that the effects of carrion are primarily driven by interactions with consumers rather than bottom‐up processes. Additionally, restricting obligate vertebrate scavenger access to increasing amounts of carrion biomass shifted the net effects of the carrion on the plant community by limiting perennial vines. Impairment of the herbivore functional role released plants from top‐down control, increasing plant growth and survival. Our experiment indicates that top‐down forces may have strong effects on plant communities following MMEs. As such, the global increase in wildlife MMEs may have broad consequences on ecological communities, not only on the species affected. Read the free Plain Language Summary for this article on the Journal blog.