Trophic Cacades Can Greatly Effect Carbon Cycling for an Ecosystem

Trophic cascade alters ecosystem carbon exchange

Authors:

1. Michael S. Strickland (a,b)
2. Dror Hawlena (c)
3. Aspen Reese (a,d)
4. Mark A. Bradford (a)
5. Oswald J. Schmitz (a)

Affiliations:

a. School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511

b. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

c. Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israel

d. Department of Biology, Duke University, Durham, NC 27708

Abstract:

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 an initial change in total plant or herbivore biomass, the cascading effects of predators in this system begin to affect carbon cycling through enhanced carbon fixation by plants. Prolonged cascading effects on plant biomass lead to slowing of carbon loss via ecosystem respiration and reallocation of carbon among plant aboveground and belowground tissues. Consequently, up to 1.4-fold more carbon is retained in plant biomass when carnivores are present compared with when they are absent, owing primarily to greater carbon storage in grass and belowground plant biomass driven largely by predator nonconsumptive (fear) effects on herbivores. Our data highlight 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.