Soil acidity, ecological stoichiometry and allometric scaling in grassland food webs

Christian Mulder,James J Elser

doi:10.1111/j.1365-2486.2009.01899.x

Abstract

The factors regulating the structure of food webs are a central focus of community and ecosystem ecology, as trophic interactions among species have important impacts on nutrient storage and cycling in many ecosystems. For soil invertebrates in grassland ecosystems in the Netherlands, the site-specific slopes of the faunal biomass to organism body mass relationships reflected basic biochemical and biogeochemical processes associated with soil acidity and soil C : N : P stoichiometry. That is, the higher the phosphorus availability in the soil, the higher, on average, the slope of the faunal biomass size spectrum (i.e., the higher the biomass of large-bodied invertebrates relative to the biomass of small invertebrates). While other factors may also be involved, these results are consistent with the growth rate hypothesis from biological stoichiometry that relates phosphorus demands to ribosomal RNA and protein production. Thus our data represent the first time that ecosystem phosphorus availability has been associated with allometry in soil food webs (supporting information available online). Our results have broad implications, as soil invertebrates of different size have different effects on soil processes.

Highlights

Biological stoichiometry (Elser et al, 1996, 2000a, b; Sterner & Elser, 2002) is the study of the balance of energy and multiple chemical elements in living systems
A central idea of biological stoichiometry is the growth rate hypothesis (GRH), which proposes that variation in C : N : P ratios among organisms reflects differential allocation to P-rich ribosomal RNA in support of rapid growth rate
To evaluate the possible impacts of soil conditions on the structure of soil food webs we examined the relationships between soil pH and C : N : P ratios and the regression slopes of both the faunal biomass spectra and the mass–abundance planes for a large number of grassland soils encompassing broad ecological gradients in the Netherlands

Summary

Introduction

Biological stoichiometry (Elser et al, 1996, 2000a, b; Sterner & Elser, 2002) is the study of the balance of energy and multiple chemical elements in living systems. Fast-growing taxa have low C : P and N : P biomass ratios, making them more susceptible to P-based stoichiometric food quality constraints (Elser et al, 2000b; Sterner & Elser, 2002). R 2009 Blackwell Publishing Ltd potential deterministic extinction of P-rich herbivores (Perez-Moreno & Read, 2001; Sterner & Elser, 2002). Many of these ideas have been extensively explored in aquatic systems (Blanco et al, 1998; Sterner & Schulz, 1998; Gamble et al, 2006; Eyto & Irvine, 2007). The size spectra of different clades in terrestrial ecosystems have traditionally been studied separately, often from an entomological perspective

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