Nutrient availability is a major constraint on plant production and carbon storage in arctic ecosystems but knowledge on the decomposer food web interactions and their effect on nutrient cycling is scarce. We manipulated the soil food web at two contrasting subarctic sites, a low altitude heath and a high altitude fell-field. The influx of nutrients and energy in the soil was increased by addition of fertiliser nitrogen, phosphorus and potassium and of labile carbon (sugar). In addition, two bactericides (penicillin and streptomycin) and a fungicide (benomyl) were applied to manipulate the bacterial and fungal component of the soil. Experiments were carried out in a factorial design with repeated additions over four growing seasons. The present study investigated the nematode fauna and the effects of the manipulations on the abundance of nematode species. Fertilisation resulted in an increase of general opportunists, especially Aphelenchoides. Application of carbon or bactericides had only minor impact on the nematode community. In contrast, the fungicide was very toxic to non-target organisms and greatly reduced the abundance of most nematode species, although Acrobeloides buetschlii showed tolerance and greatly increased in number. At both sites, Eudorylaimus was most affected by the treatments. Generally the manipulations performed resulted in a significant increase in stress tolerant or competitive dominant nematode species.

In: Nematology