Are acid-tolerant Collembola able to colonise metal-polluted soil?
Résumé
A short-term microcosm experiment was carried out to determine whether acid-tolerant collembolans are able to colonise metal-polluted soil. Polystyrene boxes were divided into two compartments by a perforated wall allowing free passage of soil fauna and preventing physical contact between soil substrates. All compartments were filled either with an acid dysmoder (pH 4.4) collected in a beech forest from Belgian Ardennes (Willerzie, Belgium) or with one of three neutral polluted soils (P1-P3) collected in the Bois des Asturies, along a metal-pollution gradient downwind of a zinc smelter (Auby, France). Different combinations were established, with five replicates each, and were incubated for 3 weeks at 15 degreesC, in darkness. Afterwards, Collembola were extracted and determined to the species level. It appeared that populations from the acid soil colonised the neutral soil polluted by heavy metals. Within 3 weeks, the number of species increased in compartments filled with the most heavily polluted soils (P2, P3) when they were in contact with the acid soil. However, colonisation was effected by only a few individuals. At the species level, the onychiurid Protaphorura eichhorni and the isotomid Folsomia quadrioculata colonised the polluted soil. For Protaphorura eichhorni the migration rate was highest when the soil was the least polluted (P1), while Folsomia quadrioculata showed a higher rate of dispersion to heavily polluted soil (P2) compared with the least polluted soil (P1). This behaviour could be explained by the humus form which was a mull in P1, more compact than the mor observed in P2 and P3, the physical structure of which approaches that of the dysmoder. Our observations indicate that both species are more affected by soil structure than by pollution.
Domaines
Science des sols
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