After‐life effects: living and dead invertebrates differentially affect plants and their associated above‐ and belowground multitrophic communities

Abstract

Above–belowground (AG–BG) studies typically focus on plant‐mediated effects inflicted by living organisms. However, animal cadavers may also play an important role in AG–BG interactions. Here, we explore whether living and dead foliar‐feeding and soil‐dwelling invertebrates differentially affect plants and their associated AG and BG multitrophic communities.In a mesocosm study we separated effects of living and dead locusts (AG herbivores) and earthworms (BG detritivores) on experimental multitrophic communities consisting of eight plant species, an AG aphid and parasitoid community and a BG nematode community. We measured root and shoot biomass and determined plant community composition and densities of aphids, parasitoids and nematodes.Living locusts decreased total shoot and root biomass in the mesocosms, whereas living earthworms enhanced total root biomass. Cadavers of both invertebrates strongly increased total root and shoot biomass, and changed the plant community composition mainly via enhanced growth of grasses. Earthworm cadavers affected plant biomass and community composition more strongly than their living counterparts, while this was reversed for locusts. Structural equation models showed that aphids and parasitoids were influenced via changes in plant community composition. Nematode densities in the soil, especially those of bacterivorous and entomopathogenic nematodes, were strongly increased by dead invertebrates, but unaffected by living ones.We conclude that effects of invertebrates on plant growth and densities of AG and BG organisms strongly depend on whether the invertebrates are dead or alive. Remarkably, invertebrate cadavers may inflict even stronger effects than their living counterparts. Hence, our study reveals an important, but often neglected, role of animal cadavers in AG–BG studies.