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

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 hig...