Effect of pedestrian activity on earthworm populations of two forests in Switzerland
1992
Cuendet, G.
The effect of pedestrian activity on earthworm populations was investigated in two forests in a periurban region. In the first case, a deciduous forest, pedestrian activity affects a 2 m wide path. Simultaneous sampling with the formalin method in trodden and non-trodden soils revealed that pedestrian activity paradoxically increased total earthworm density and biomass, but reduced diversity. The mechanical and quite rapid mixing of litter into the top soil by pedestrian activity drastically decreased the presence of epigeic earthworms. At the same time, one anecique species and, to a lesser extent, one endogeic species flourished. Absence of epigeic competition and better conditions for the juveniles of the anecique species may explain this difference. The second forest, at higher altitude, is characterized by an important presence of coniferous trees. The trodden surface was investigated much larger than in the first case and pedestrian activity was more important than in the first case. It was found that the earthworm population almost totally disappeared in the trodden soil. The principal reason for this drastic reduction must be the absence of undergrowth and a litter composed mostly of coniferous needles. In conclusion, if pedestrian activity is relatively light and does not much modify the composition of the litter mixed into the top soil, it may significantly increase the density and the biomass of some anecique and endogeic species, while decreasing those of epigeic species. If pedestrian activity is important and coniferous trees are present, the earthworm population decreases drastically.
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