Few organisms of the macro – and mesofauna live in the raw soils. The pioneer sites are still free of earthworms. Generally, no microbiological activity was found on these sites (average soil respiration: 0.04 mg O2/100 g dry matter/h). In the shrub and woodland sites, the level of microbiological activity ranged between mean moderate and high (average soil respiration from 0.1-1.2 mg O2/100 g TS/h). Due to ongoing acidification, a reduction in microbiotic activity is to be expected. This would enhance fungi instead of bacteria and would subsequently decrease the decomposition rate of litter.
In the shrub site SR and woodland site WZ, the population density of lumbricids is still low with 6-12 individuals per square meter (Fig. 3). The lack of litter consumers, particularly big, deep-digging earthworms, leads to a “decomposition jam” and an accumulation of litter and thick raw humus forms. Such raw humus forms are typical of the acidic, low-nutrient soils that are found at the site WZ. The lumbricid presence at WR is completely different. Here, big, deep-digging earthworms occur abundantly throughout the mineral soil although they live under the same acidic conditions as the previous cases (pHCacl2<4). In contrast to the lumbricids, the enchytraeids indicate a future change in the composition of the soil macrofauna in response to acidic soil conditions. The dominant species Cognet – tia sphagnetorum and Marionina clavata are typical micro-annelids of acidic top layers.
At the rubble site SA, the number of lumbricids is typical of moderately alkaline pH values. Surprisingly, there is a clear dominance of animals that usually live in humus layers over those living in mineral-soil layers, although we recorded no significant humus layer at this site.