Disturbance regulates the density–body mass relationship of soil fauna

Theory on the density-body mass (DBM) relationship predicts that the density of animal species decreases by the power of −0.75 per unit increase in their body mass, or by the power of −1 when taxa across trophic levels are studied. This relationship is, however, largely debated as the slope often deviates from the theoretical predictions. Here, we tested the ability of the DBM relationship to reflect changes in the structure of communities subjected to an anthropogenic disturbance. The slope would become less steep if smaller animals were more impacted by the disturbance than the larger ones, whereas the slope would become steeper if larger animals were more affected than the smaller ones. We tested the changes in the DBM relationship by sampling soil fauna, i.e. nematodes, Collembola and larger arthropods, from a semi-arid grassland before and after spraying diesel fuel as disturbance. We applied three different treatments: a control, a light disturbance and an intense disturbance. We ...