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Trophic Cascades

  1. Daniel S Gruner

Published Online: 15 MAR 2013

DOI: 10.1002/9780470015902.a0003183.pub2

eLS

eLS

How to Cite

Gruner, D. S. 2013. Trophic Cascades. eLS. .

Author Information

  1. University of Maryland, College Park, Maryland, USA

Publication History

  1. Published Online: 15 MAR 2013

Abstract

Trophic cascades in ecological communities are defined as the propagation of indirect effects between nonadjacent trophic levels in a food chain or food web. Typically, cascades are driven by predation from the top-down, with altered herbivore densities mediating the ultimate effects on the biomass of primary producers. Predator traits and nonconsumptive changes in the behaviour of prey also can propagate cascading indirect effects, and variation in nutrients or energy at the base of food webs may mediate cascades from the bottom-up. Significant debate has revolved around the relative dynamical strength of top-down versus bottom-up forces and over the importance of trophic cascades in different aquatic and terrestrial ecosystems. Polarisation has eased with the increased availability of experimental and comparative case studies, meta-analytic syntheses of these data and development of theory. The basic conceptual construct of trophic cascades has been applied to classical biological control of agricultural pests, biomanipulation of lakes and streams and the conservation and restoration of apex predators for fisheries and wildlife management.

Key Concepts:

  • Limited nutrient availability and high C:N and C:P stoichiometry can constrain biomass turnover and the strength of trophic cascades.

  • Many lake and stream ecosystems support four trophic levels, with piscivorous fish ultimately suppressing phytoplankton in a consumptive interaction chain.

  • Trophic cascades can occur via direct consumption and density reductions of prey and through behavioural changes in prey foraging from predation risk.

  • Fisheries intensification has selectively reduced top predators and large-bodied species and reduced the length of oceanic food chains.

  • Reintroduction of top predators, such as wolves, to the American west has facilitated recruitment of woody shrubs and trees and reduced stream erosion.

  • Long-term studies are critical to testing for and identifying trophic cascades on landscape and regional spatial scales.

Keywords:

  • food webs;
  • herbivory;
  • indirect effects;
  • nutrient cycling;
  • omnivory;
  • predation;
  • primary productiony;
  • top-down control;
  • bottom-up forces;
  • trophic interactions