Colonisation by Enchytraeidae, Collembola and Acari in Sterile Soil Samples with Adjusted pH Levels

Soil animals were allowed to colonise sterile soil samples from three soil types: raw humus, poor mull and rich mull. Within each soil type, samples adjusted to three different pH levels were offered. Soil pH significantly influenced the success of colonisation in the following number of species: Collembola 7, Oribatei 8 (minimum), Mesostigmata 3, Astigmata 1, Enchytraeidae 3, and Lumbricidae 1. In all three soils, there were reactions both in favour of acidification and of liming. The largest number of species reacting to the treatments was found in raw humus, where the most marked pH gradient occurred. When a species reacted to both lowered and raised soil pH, these reactions were always opposite. Within the same species, reaction patterns in different soil types supported each other. High numbers of Acari in acidified raw humus was mainly due to Tectocepheus velatus Michael, Nothrus silvestris Nicolet and Schwiebea cf. nova (Oudemans). Age structure indicated that soil pH influenced reproductive success. For several species, reactions were supported by current field experiments and information on the species' natural occurrence.