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National Center for Ecological Analysis and Synthesis

Project Description

Trophic structure, the partitioning of biomass among organisms at different positions in a food web, varies both within and among ecosystems. However, the causes of this variation are poorly understood. Elton's "pyramid of numbers", where primary producers dominate and consumer densities decrease as trophic levels become more remote from the base of production, applies well to most terrestrial systems. However, many aquatic ecosystems apparently violate Elton's rule with inverted biomass pyramids, or ratios of heterotroph-to-autotroph biomass (H:A) greater than one. In this proposal, we describe synthetic work aimed at understanding differences in trophic structure and the relative strength of bottom-up and top-down inputs between diverse freshwater, marine and terrestrial ecosystems. We will test candidate hypotheses for this variation based on factors known to distinguish food webs in the two habitats, such as nutrient limitation and turnover rates, productivity (quantity) and nutrient stoichiometry (quality). Meta-analysis of local-scale herbivore manipulation experiments will be integrated with theoretical development of food web models, and with larger-scale temporal and spatial patterns from resource gradients. This work will move us closer to a comprehensive trophic-dynamic theory, unified across taxa and ecosystem types. It will also increase our mechanistic understanding of how human impacts, such as eutrophication or predator extirpation, propagate or attenuate in ecosystems through trophic interactions.

Principal Investigator(s)

Jonathan B. Shurin, Daniel S. Gruner, Helmut Hillebrand

Project Dates

Start: April 30, 2007

End: September 12, 2008



Benjamin Bolker
University of Florida
Elizabeth T. Borer
Oregon State University
Matthew E. Bracken
James H. Brown
University of New Mexico
Bradley J. Cardinale
University of California, Santa Barbara
Just Cebrian
University of South Alabama
Elsa E. Cleland
University of California, Santa Barbara
Kathryn L. Cottingham
Dartmouth College
Claire de Mazancourt
McGill University
James J. Elser
Arizona State University
Daniel S. Gruner
University of Maryland, College Park
W. Stanley Harpole
Iowa State University
Helmut Hillebrand
University of Cologne
Jacqueline T. Ngai
University of British Columbia
Stuart A. Sandin
University of California, San Diego
Eric W. Seabloom
Oregon State University
Jonathan B. Shurin
University of British Columbia
Jennifer E. Smith
University of California, Santa Barbara
Melinda D. Smith
Yale University
Elizabeth M. Wolkovich
Dartmouth College


  1. Journal Article / 2013

    Global biogeography of autotroph chemistry: Is insolation a driving force?

  2. Journal Article / 2019

    Plant species natural abundances are determined by their growth and modification of soil resources in monoculture