Summary Band 31

Geissen, V.: Reactions of soil fauna (Lumbricidae, Annelida; Collembola, Arthropoda) to varying nutrient and toxic element contents of forest soils after liming and fertilization. Bonner Bodenkundl. Abh. 31 (2000) 

This study investigates the numerous interrelations between abiotic and biotic parameters of deciduous and spruce forest soils after liming and P,K fertilization. Under study were in particular the reactions of microflora, lumbricidae and collembola on varying contents in mobile basic cations and potentially toxic elements such as aluminium and heavy metals. Furthermore, we tried to reestablish endogeic species of lumbricides in these forest soils.
In the years 1993 to 1997 we conducted a field study on stagnic alisols of loess in the Kottenforst near Bonn, Germany. We established six variants in an oak-hornbeam and six in a spruce forest  and applied different amounts of lime (0, 3, 6, 9 and 15 t dolomite ha-1, partly combined with P, K fertilization).
Liming led to increasing pH values and increasing contents in mobile basic cations whereas the content in mobile heavy metals and aluminium decreased in most cases. In the spruce forest these effects were predominante in the organic layers, whereas in the deciduous forest soils the treatment also influenced soil chemical parameters in the mineral soil down to a depth of 20 cm. The most distinct changes were achieved in those cases where the highest amounts of dolomite were applied.
The treatments produced a definit positive effects on microflora and endogeic lumbricides. However, the effects were strongly dependent on the initial soil chemical status. We observed significantly positive correlations between the biomass of microflora and endogeic lumbricides on the one hand and mobile basic cations on the other hand whereas mobile heavy metals and aluminium showed negative correlations. In the spruce forest the application of 15 t dolomite ha-1 reduced the abundance in epigeic species. In both forest types the establishment of endogeic lumbricides in combination with liming was sucsessfull.
During the period of experimentation we determined 99 collembolan species out of a lot of 35000 individuals. The abundances in the spruce forest were significantly higher than in the deciduous forest. Only six collembolan species in the deciduous forest and eight species in the spruce forest showed obvious reactions to the treatments and correlations with soil chemical parameters. The collembolan fauna was obviously well adapted to a wide range of soil chemical parameters in the forest soils.
In the case of our investigations we noted that the decomposition rate was mainly influenced by the activity of the microflora while the impact of the soil fauna was small. In the spruce forest the application of 9 or 15 t dolomite ha-1 in combination with P,K fertilization significantly increased decomposition rates. In the deciduous forest decomposition was highest in the plots treated with 6 t dolomite   ha-1.
In both forest types the effects of the treatments were strongly dependent on the initial status of the soil. Therefore, it is not possible to fix a general amount of lime and fertilizer needed to improve forest soils so as to reach a pH(CaCl2) > 4 - 4,5. It should be calculated in relation to the individual location and its chemical status.
For further investigations in forest soils we recommend to use microflora, lumbricides and decomposition rates as indicators for changes in soil biota.