The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities. The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning, and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to the entire community is high under low soil phosphorus content and causes shifts in the mass-abundance relationships and in the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according to resource availability and can predict environmental shifts in ecologically meaningful ways. ; A.G.R. gratefully acknowledges support by a Beaufort Marine Research Award by the Marine Institute, under the Sea Change Strategy and the Strategy for Science, Technology and Innovation, funded under the Irish National Development Plan (2007-2013). C.M. and H.A.D.H. were supported by the RIVM Directorate (QERASS/860703 and EIA S/607001) and by the Scientific Advisory Committee of the Netherlands Ministry of Housing, Spatial Planning, and Environment (VROM).