Predator Effects On Carbon Cycling in An Old Field Ecosystem.

Trophic cascades –the indirect effects of carnivores on plants mediated by herbivores— are common across ecosystems but their influence on biogeochemical cycles, particularly the terrestrial carbon cycle, are largely unexplored. Here, using a ¹³C pulse-chase experiment, we demonstrate how trophic structure influences ecosystem carbon dynamics in a meadow system. By manipulating the presence of herbivores and predators we show that even without a change in total plant or herbivore biomass, that cascading effects of predators in this system affects carbon cycling through enhancement of carbon fixation by plants and slowing of carbon loss via ecosystem respiration. These changes cause up to 1.4-times more carbon retention in aboveground and belowground plant biomass when carnivores are present compared to absent. This is primarily due to greater C storage in grass and belowground plant biomass driven by non-consumptive predator effects. This highlights the influence that the mere presence of predators, as opposed to direct consumption of herbivores, can have on carbon uptake, allocation, and retention in terrestrial ecosystems.