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Data from: Salty, mild, and low plant biomass grasslands increase top-heaviness of invertebrate trophic pyramids

Welti, Ellen1; Kuczynski, Lucie1; Markse, Katharine1; Sanders, Nathan2; de Beurs, Kirsten1; Kaspari, Michael1

Published Mar 13, 2021 on Dryad. https://doi.org/10.5061/dryad.612jm6411

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Mar 13, 2021 version files 43.26 KB

Abstract

Aim Multiple hypotheses predict how gradients of nutrient availability, plant biomass, and temperature shape trophic pyramids. We aim to disentangle the simultaneous influence of those different factors and their indirect effects on trophic structure and individual trophic levels.

Location United States

Time period 2017

Major taxa studied Invertebrates

Methods To examine differences in trophic pyramid shape and abundance within trophic levels across ecological gradients, we used a structural equation modeling approach to analyze 54 standardized surveys of invertebrate communities in North American grasslands. We tested for the direct and indirect effects of plant biomass, temperature, sodium (Na), other essential elements (e.g. N, P and K), and toxic heavy metals, (e.g. Ar and Pb) in plant tissue on individual trophic levels as well as on the global trophic pyramid shape estimated as the Community Trophic Mean (CTM).

Results Plant sodium increased CTM, indicating that high plant sodium concentrations are associated with top-heavy invertebrate trophic pyramids. Increased plant biomass resulted in higher proportions of herbivores compared to higher trophic levels. Finally, increasing temperature resulted in more top-heavy trophic pyramids, although effects were weaker than those of plant-related factors. Overall, plant biomass, temperature and plant chemistry directly and indirectly affected the abundances within different trophic levels, highlighting the complexity of factors regulating trophic structure.

Main conclusions Trophic structure of grassland invertebrate communities is strongly influenced by plant sodium, plant biomass, and to a lesser extent, temperature. Grasslands occupy 30% of the Earth’s terrestrial surface and are an imperiled ecosystem due to conversion to row crop agriculture. As biogeochemistry and temperature in the Anthropocene are increasingly modified, our results have considerable implications for the trophic structure of future grassland communities.