A cross‐ecosystem comparison of the strength of trophic cascades

TLDR

Trophic cascades, the indirect effects of predators on plants via herbivores, are common across diverse food webs but their magnitudes vary widely. The authors compared herbivore and plant responses to predator manipulations across 102 field experiments in six ecosystems, including lentic, marine, stream benthos, plankton, and terrestrial systems. Predator effects differed markedly among systems, being strongest in benthic aquatic habitats and weakest in marine plankton and terrestrial webs; herbivore responses were generally larger and more variable than plant responses, indicating attenuation at the plant–herbivore interface, and overall top‑down control of plant biomass was stronger in water than on land, with aquatic systems showing as much variation as wet versus dry systems.

Abstract

Abstract Although trophic cascades (indirect effects of predators on plants via herbivores) occur in a wide variety of food webs, the magnitudes of their effects are often quite variable. We compared the responses of herbivore and plant communities to predator manipulations in 102 field experiments in six different ecosystems: lentic (lake and pond), marine, and stream benthos, lentic and marine plankton, and terrestrial (grasslands and agricultural fields). Predator effects varied considerably among systems and were strongest in lentic and marine benthos and weakest in marine plankton and terrestrial food webs. Predator effects on herbivores were generally larger and more variable than on plants, suggesting that cascades often become attenuated at the plant–herbivore interface. Top‐down control of plant biomass was stronger in water than on land; however, the differences among the five aquatic food webs were as great as those between wet and dry systems.