Allometry of soil food webs and C:N:P stoichiometry

Allometry integrates the biological and physicochemical constraints that occur in terrestrial ecosystems. We investigated the relationships between body-mass and numerical abundance of all invertebrates occurring under 15 organic pastures sown with N₂-fixing legumes, 10 mature grasslands and 10 heathlands in The Netherlands. Here we show how food webs respond to variations in nutrient limitation and microbial resources. Log-linear models, in particular, describe how the allometric slopes of food webs reflect soil C:N:P stoichiometry. The nitrogen-to-phosphorus ratio explains most trends, among others the number of trophic links and the contributions of micro– and mesofauna to the food-web structure. We conclude that soil P-deficiency affects the consumer–resource body-mass ratios, as our results support a different response of invertebrates to the supply of nutrients. This study can help bridge the gap between community structure and function, and may inform improved agricultural policy and restoration ecology.