Colonization of heavy metal-polluted soils by Collembola: preliminary experiments in compartmented boxes

9 10 Two-week laboratory experiments were carried out in plastic boxes separated in two connected 11 compartments filled with a neutral soil (mull humus) at pH 7.7 and an acid soil (moder humus) at pH 12 4.3, containing their original faunas. Migration of Collembola from one compartment to the other was 13 allowed through a perforated wall. The mull was contaminated with three concentrations of lead (as 14 lead acetate) at 50, 6,000 and 60,000 ppm. When combined with moder in the adjacent compartment, 15 6 times more individuals and 5 times more species were observed in the mull at the highest 16 concentration applied, compared to mull combined with itself. Parisotoma notabilis proved to be highly 17 sensitive to lead, and shifted to the moder compartment even at the lowest concentration. Densities of 18 other mull species such as Pseudosinella alba were affected by medium to high concentrations of lead 19 but these species did not move to the moder soil despite their high motility. Acidophilic species living 20 in moder only, such as Willemia anophthalma, Xenylla tullbergi, Proisotoma minima and Xenylla 21 tullbergi, colonized contaminated mull treatments with densities increasing with lead concentrations 22 but the result of this process was erratic. Folsomia manolachei was present in both humus forms but 23 was much more abundant in the moder. This species colonized mull at medium to high lead 24 concentrations, where it restored totally or partly its original abundance in the uncontaminated mull. 25 These results suggested differences between mull and moder populations of Folsomia manolachei. 26