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Summary Band 34

Schöning, Alexander: Influence of chemical properties of forest soils on earthworm populations – implications for soil liming. Bonner Bodenkundl. Abh.34, (2000), 343 S.

 

The influence of soil-chemical properties on earthworms was investigated in soils of loess in the Kottenforst area near Bonn. Limed and partly P,K-fertilized plots as well as untreated plots were used for this purpose. The investigation focused on the mobile, i.e. potentially bio-available element fractions.
 For the liming-/fertilizing-experiment, six differently treated plots each in deciduous and spruce forest were established at acidic Stagnic Alisol sites in 1994/95. The treatments were 0, 3, 6 t dolomite/ha without P,K-fertilizer and 6, 9, 15 t dolomite/ha combined with P,K-fertilizer. In order to re-establish endogeic and anecic lumbricid species, we tried to colonise these species in the different plots. Samples were taken every six months during 1993 to 1998.
 Depending on the amount of lime, especially in the deciduous forest, the treatments led to significant positive changes in soil chemical properties. In the soil depths which were influ-enced by liming both the pH(CaCl2) and the content of mobile Ca and Mg increased, whereas the content of mobile heavy metals and Al was reduced. The content of mobile P, K and S only changed negligibly even in the P,K-fertilized plots. Neither decomposition of humus stock nor leaching of NO3 could be observed with the sampling method used in our investigations. How-ever, a slight leaching of some heavy metals and Al could not be ruled out. Corresponding to the different depth effects of the treatments on the soil chemical properties, their influence on the lumbricids was also different in deciduous and spruce forest. In the deciduous forest the number of species as well as abundance and biomass, especially of the endogeic species, already in-creased during the first year after the treatments. In the spruce forest, however, lumbricid abun-dance and biomass increased only 3 years after the treatments.
 The investigation of the untreated plots showed a large variation of soil chemical prop-erties. Accordingly, big differences in the earthworm populations were observed. Representa-tives of epigeic, intermediate, endogeic and anecic lumbricids were found.
 The correlation analysis for the whole data indicated that there is a strong relationship between the genus Aporrectodea and soil chemical properties of the top soil. The “acid compo-nent” extracted by major component analysis was found to be the main factor of influence. This component includes the pH(CaCl2) as well as the content of mobile Ca, K, Fe, Zn, Al, Cd and Pb. The genus Dendrobaena and the species L. rubellus proved to be highly independent from the examined soil chemical properties. The anecic species L. terrestris also showed no close relationship to soil chemical properties in the top soil. Obviously L. terrestris is able to compensate for relatively unfavourable conditions in the top soil by favourable conditions in the bottom soil.
 We concluded that a significant improvement of soil chemical properties with simulta-neous promotion of especially endogeic lumbricids can only be achieved at pH values of at least 4.5. In order to attain this target pH value, different amounts of lime are required depending on the soil properties. In any case liming should be repeated at intervals of a few years.

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