TABLE CONTENTS

Modeling Soil Properties and Organisms’ Interactions by Food Webs
Mulder, C. (1) & G.W. Yeates (2)
(1) Ecological Risk Assessment, RIVM, Box 1, Bilthoven, 3720 BA, The Netherlands; (2) Landcare Research,
Private Bag 11052, Palmerston North 4442, New Zealand
In the Netherlands, we developed a biological indicator for the sustainability of soil use and
ecosystem resilience, based on belowground food-web interactions and ecological processes
of microorganisms, microfauna and mesofauna. We wish to introduce a new approach to the
diversity-stability debate using a method for complete comparison of the structure and
functioning of allometrically-scaled food webs, properties of soil systems and environmental
impact at different locations.
We evaluated the biodiversity, multi-trophic dynamics, trait distribution, and numerical
abundance of the belowground community food webs using non-metric multidimensional
scaling and cluster analysis, and investigated the influence of management regime on the
nematofauna with multiple regression analysis and Mantel tests. Soil characteristics did not
differ significantly among the grasslands on sand, or between mature, highly-productive, and
undisturbed sites. In contrast, at all sites the taxocenes react in a significantly different way to
nutrient supplies and soil chemistry.
Our soil food webs, plotted according to a new methodology, show that prey and predators
fall near a diagonal where the mean slope of their body-mass ratio as function of their
specific abundance-ratio equals – ¾. As this negative scaling with body size is nearly
universal, we can easily predict by metabolic scaling theory the cumulative temperaturedependent
respiratory rate for multiple invertebrates within the two independent energy
pathways: the fungal channel and the bacterial channel. With this method, the decrease in the
biodiversity and populations of microbial-grazing nematodes under specific environmental
conditions can be easily illustrated by a simple comparison of regression slopes. Even the
existence of different patterns between community food webs appears to be in clear
agreement with functional differences at higher trophic level between species-poor and
species-rich soil systems.
5 th International Congress of Nematology, 2008 107