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W. Dunger und K. Voigtländer

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Wolfram Dunger Senckenberg Museum für Naturkunde Görlitz, Abteilung Bodenzoologie,
Postfach 30 01 54, 02806 Görlitz, Deutschland;


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Karin Voigtländer Senckenberg Museum für Naturkunde Görlitz, Abteilung Bodenzoologie,
Postfach 30 01 54, 02806 Görlitz, Deutschland;
 

 

Soil fauna (Lumbricidae, Collembola, Diplopoda and Chilopoda) as indicators of soil eco-subsystem development in
post-mining sites of eastern Germany – a review


Abstract

The soil zoological department of the Senckenberg Museum of Natural History Görlitz has studied immigration, colonisation and biological activity of main groups of soil fauna on brown coal open-cast mine sites in eastern Germany for nearly half a century (1960 to 2006). The present paper provides a review and data on the long-term development of primary succession, mainly in a real-time series of soil macrofauna (especially Lumbricidae and Myriapoda) and soil microarthropods (especially Collembola).
The results were obtained for the most part from Upper Lusatian dumps (district Görlitz) with predominantly loamy, Pleistocene substrata, compared with Lower Lusatian dumps (district Cottbus) with predominantly acid, sandy, Tertiary substrata. Besides the substrata, the vegetation (promoted by rehabilitation) determines the process of colonisation and development of soil faunal assemblages. In particular, the difference between afforestation with deciduous, soft leaved trees or with coniferous or hard-leaved trees was demonstrated in the different examples.
In the study sites, only 7 species of earthworms regularly take part in the colonisation of mine sites; 3 further species are found sporadically. They took normally 3 to 20 years to immigrate and establish populations under good conditions during10 to 30 years. In the last few years of this period an extremely high abundance of 100 gm‾² was observed with a subsequent reduction to the probable ‘predisturbance level’ (30–60 gm‾²) 40 to 54 years after reclamation. Very characteristic is the distribution of life forms during the succession, moving from a preponderance of epigeics in the pioneer period to the clear dominance of anecics in the progressed phase (organisation period). Comparision of the quantitative data from different mine sites and site ages allows the use of earthworms as indicators of mine-site soil quality.
Microarthropods invade, partly as aerial plankton, mine sites very quickly but have a different, species-dependent colonisation behaviour. Rapid production of deciduous litter after afforestation and the absence of competition from earthworms enable microarthropods to quickly develop a ‘pioneermaximum’ with highest abundances and species diversity, followed by a minimum density after the incorporation of the ectohumus layer into topsoil by earthworms. Merely 30 to 50 years later microarthropods again reach an abundance as found in the control native woodlands. The study of colonisation behaviour typical of 113 species of Collembola indicated that there were eight different colonisation groups of springtails that were useful in characterising different stages of mine-site development. Compared with ‘native’ reference woodlands, the identity of collembolan species composition is highest in the 10th year after rehabilitation but declines later. There are ‘mine-site-phobic’ species – elsewhere very common – which behave in a stochastic ‘variable’ manner. As a result, the collembolan species composition of well-developed mined woodlands still show a lack of some species even after half a century following mining.
A further intensive study was made with millipedes and centipedes which need – like earthworms – a longer time for immigration. The presence of saprophagous millipede species showed a clear succession in parallel with mine-site development, but there is no species with true pioneer behaviour. Centipedes – with Lamyctes emarginatus as a true pioneer – as predators behave less predictably; Geophilomorphs, hunting in the subsoil, are the last to invade. After 50 years of development of mine-site woodlands, five species of millipedes and six species of centipedes, though common in adjacent reference woodlands, had not yet colonised the mine sites. Comparisons between myriapod assemblages at mine sites in Upper and Lower Lusatia that had different soil and age conditions revealed that myriapods are good indicators of biological soil quality and are reliable and easy to use.
The role of saprophagous fauna, esp. earthworms, in SOM decomposition was studied using metabolic parameters for the potential level of decomposition (DLZpot). For this, laboratory data of the metabolic equivalents (ME) of the studied saprophagous groups of the microfauna and macrofauna were combined with the present biomass of these groups (in gm‾²) and divided by the yearly SOM-production of litter and soil layer of vegetation (DLZpot). Minimal litter decomposition occurred during the pioneer optimum of microarthropods (3rd to 5th year) in deciduous-afforested sites. Later the total SOM decomposition becomes essentially higher up to 75 %. Here the contribution of earthworms was about 98 %, whereas the role of millipedes and dipteran larvae can be ignored. In pine afforestations, the decomposition efficiency of the (macro-)fauna was 4.5 to 7 times lower than calculated for deciduous mine sites.

Keywords

substratum types, recultivation, immigration, colonisation, succession, SOM decomposition, ecofaunistical groups, metabolic equivalences


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