WHAT DETERMINES THE STRENGTH OF A TROPHIC CASCADE

By Elizabeth T. Borer, Eric W. Seabloom, Jonathan B. Shurin, K. Anderson, Carol Blanchette, Bernardo R. Broitman, S. D. Cooper, B. Halpern. 2005

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Trophic cascades have been documented in a diversity of ecological systems and can be important in determining biomass distribution within a community. To date, the literature on trophic cascades has focused on whether and in which systems cascades occur. Many biological (e.g., productivity : biomass ratios) and methodological (e.g., experiment size or duration) factors vary with the ecosystem in which data were collected, but ecosystem type, per se, does not provide mechanistic insights into factors controlling cascade strength. Here, we tested various hypotheses about why trophic cascades occur and what determines their magnitude using data from 114 studies that measured the indirect trophic effects of predators on plant community biomass in seven aquatic and terrestrial ecosystems. Using meta-analysis, we examined the relationship between the indirect effect of predator ma- nipulation on plants and 18 biological and methodological factors quantified from these studies. We found, in contrast to predictions, that high system productivity and low species diversity do not consistently generate larger trophic cascades. A combination of herbivore and predator metabolic factors and predator taxonomy (vertebrate vs. invertebrate) explained 31% of the variation in cascade strength among all 114 studies. Within systems, 18% of the variation in cascade strength was explained with similar predator and herbivore char- acteristics. Within and across all systems, the strongest cascades occurred in association with invertebrate herbivores and endothermic vertebrate predators. These associations may result from a combination of true biological differences among species with different phys- iological requirements and bias among organisms studied in different systems. Thus, al- though cascade strength can be described by biological characteristics of predators and herbivores, future research on indirect trophic effects must further examine biological and methodological differences among studies and systems.

Subfields: Ecology, Ecology, Evolution, Behavior and Systematics, Nature and Landscape Conservation

View Paper: https://www.semanticscholar.org/paper/5e2555aca04adc299d4aeee67eb6491b9ee1a22c

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Citations in the corpus

Stoichiometrically Explicit Food Webs: Feedbacks between Resource Supply, Elemental Constraints, and Species Diversity (2009, background): “Controversy centers on pronounced variation in cascade strength seen among ecosystems, and several nonstoichiometric hypotheses might explain this broad-scale variation (Borer et al. 2005, Shurin et al. 2002, Shurin & Seabloom 2005).”
Status and Ecological Effects of the World’s Largest Carnivores (2014, background): “IUCN, The IUCN Red List of Species, Version 2012.2, http://www.iucnredlist.org; downloaded April 2013.”
Food for thought: supplementary feeding as a driver of ecological change in avian populations (2008, background): “However, there have been very few studies on this phenomenon, probably because detecting and identifying cascading effects is notoriously difficult (Borer et al. 2005).”
A brown‐world cascade in the dung decomposer food web of an alpine meadow: effects of predator interactions and warming (2011, background): “As shown in several reviews (Schmitz et al. 2000, Shurin et al. 2002, 2006, Borer et al. 2005, Duffy et al. 2007), the strength of trophic cascades depends on herbivore species diversity, carnivore type (vertebrate vs. invertebrate), ecosystem type (terrestrial vs. aquatic systems), primary…”
Biodiversity and the functioning of seagrass ecosystems (2006, background): “Changes in vertical diversity (e.g. food chain length) often strongly influence ecosystem properties through changing trophic interactions (e.g. Pace et al. 1999, Shurin et al. 2002, Borer et al. 2005).”
Restoring Yellowstone’s aspen with wolves (2007, background): “The strength of top-down forces (trophic cascades) in terrestrial food webs is highly debated, as few examples exist illustrating the cascading effects of large mammalian carnivores in structuring terrestrial ecosystems (Ripple and Beschta, 2004a; Borer et al., 2005; Hebblewhite et al., 2005; Ray ”
Herbivory on freshwater and marine macrophytes: A review and perspective (2016, background): “…as variation in plant productivity, nutritional quality, stoichiometry, resistance and tolerance to grazing (Cebrian et al., 2009); and top-down effects, such as variation in herbivore abundance, feeding efficiency, size, taxonomy, mobility, metabolism and predator effects (Borer et al., 2005).”
Trophic cascades involving cougar, mule deer, and black oaks in Yosemite National Park (2008, background): “…interactions within a foodweb can be complex and the relative strength of top-down vs. bottom-up forces can vary, the importance of trophic cascades in ecosystem processes and functions has remained controversial (Schmitz et al., 2000; Halaj and Wise, 2001; Shurin et al., 2002; Borer et al., 2005).”
Linking a cougar decline, trophic cascade, and catastrophic regime shift in Zion National Park (2006, methodology): “…the relative strength of topdown forcing versus bottom-up controls (Estes, 1996; Pace et al., 1999; Terborgh et al., 1999, 2001; Polis et al., 2000; Borer et al., 2005), there is often little consideration beyond tritrophic cascades, especially concerning potential pathways . involving changes in…”
Emergent Impacts of Ant and Spider Interactions: Herbivory Reduction in a Tropical Savanna Tree (2012, background): “Indirect positive effects of predators on plants, for example, may be influenced by interactions among trophic levels and intraguild predation and competition (Fagan 1997, Borer et al. 2005, Sanders et al. 2011).”
Large predators limit herbivore densities in northern forest ecosystems (2012, unknown): “in terrestrial ecosystems involve invertebrate communities (Borer et al. 2005).”
The functional role of biodiversity in ecosystems: incorporating trophic complexity. (2007, background): “Similar cascading effects of predator removal have 2007 Blackwell Publishing Ltd/CNRS since been documented in a wide variety of ecosystems (Pace et al. 1999; Borer et al. 2005).”
Understanding the Effects of Marine Biodiversity on Communities and Ecosystems (2007, background): “However, the range of species diversity in the studies analyzed by Borer et al. (2005) was probably insufficient to detect an effect of diversity, even if one existed.”