Terrestrial Trophic Cascades: How Much Do They Trickle?

Abstract

Although more consensus is now emerging on the magnitude and frequency of cascading trophic effects in aquatic communities, the debate over their terrestrial counterparts continues. We used meta-analysis to analyze field experiments on trophic cascades in terrestrial arthropod-dominated food webs to evaluate the overall magnitude of trophic cascades and conditions affecting their occurrence and strength. We found extensive support for the presence of trophic cascades in terrestrial communities. In the majority of experiments, predator removal led to increased densities of herbivorous insects and higher levels of plant damage. Cascades in which removing predators led to decreased herbivory also were detected but were less frequent and weaker, suggesting a predominantly three-trophic-level behavior of arthropod-dominated terrestrial food webs. Despite the clear evidence that cascades often decreased plant damage, residual effects of predation produced either no or only minimal changes in overall plant biomass. Agricultural systems and natural communities exhibited similarly strong effects of predation on herbivore abundance. However, resulting effects on plant damage and community-wide effects of trophic cascades on plant biomass usually were highly variable, and only in the managed agricultural systems did predators occasionally have strong indirect effects on plant biomass. Our meta-analysis suggests that the effects of trophic cascades on the biomass of primary producers are weaker in terrestrial than aquatic food webs.

Birds help plants: a meta-analysis of top-down trophic cascades caused by avian predators

“…When all predators of herbivores (avian, mammalian, invertebrate) are taken into consideration, meta-analyses of terrestrial tritrophic cascades have shown that predatorexclusion beneWts herbivorous arthropods more than harms plants (Halaj and Wise 2001;Mooney et al 2010), but that vertebrate carnivores usually have a stronger impact than invertebrate predators (Schmitz et al 2000). Moreover, previous reviews of terrestrial trophic cascades have often used a large variety of predators where the speciWc eVects of one predator group (e.g.…”

Plant-insect communities and predator-prey ratios in field margin strips, adjacent crop fields, and fallows

“…Huusela-Veistola (1998) also found that perennial grass strips enhance spider populations in the strip and the adjacent field, which is similar to the findings of Bayram and Luff (1993) and Jmhasly and Nentwig (1995). Bayram and Luff (1993) emphasize the role of grassy perennial strips as an overwintering site for spiders, and Halaj and Wise (2001) showed in a meta-analysis that in the majority of experiments, predator removal led to increased levels of herbivorous insects and higher levels of plant damage.…”

Ants on plants: a meta-analysis of the role of ants as plant biotic defenses

“…Although the effects of ants as terrestrial top predators and the effects of predators on plant damage and biomass have been previously reviewed through meta-analyses of trophic cascades (Halaj and Wise 2001;Schmitz et al 2000), to the best of our knowledge, a deeper and specific meta-analysis of the protective role of ants on plants has yet to be done. Therefore, we aimed to use meta-analytical methods to: (1) determine the magnitude of the effect of ant presence on herbivory rates and parameters of plant fitness, (2) investigate whether there are differences in the magnitude of those effects in tropical versus temperate regions, (3) compare the magnitude of the effects of removal of single versus several ant species, (4) compare the magnitude of the effects in relationship to different ant attractors, attractor combination and number as well as attractor position on the plant, and (5) compare the magnitude of effects on obligate ant-plants (=myrmecophytes) and facultative (=myrmecophile) relationships between ants and host plants, in both tropical and temperate regions.…”