Effects of conifer resin on soil fauna in potential wood-ant nest materials at different moisture levels

摘要

The aim of this study was to test the effect of resin on the composition of the soil fauna at high and low moisture levels. Wood ants (Formica rufa group) often collect large amounts of resin from coniferous trees and bring it to their nests. A previous study showed that resin can stimulate fungal growth, which can possibly affect fungivorous soil animals living in the nests. On the other hand, resin may also be harmful to soil animals. A laboratory incubation study was carried out using mixed needle litter from Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). Resin was added to the litter material in amounts corresponding to 25% of the litter dry weight, a resin content commonly found in ant nests. In the control series, no resin was added. The soil moisture was maintained at 60% water-holding capacity (WHC) in one series and 15% WHC in another series, corresponding to levels in moist litter and in dry ant nests, respectively. After a 70-day incubation, soil fauna was extracted and determined from a sub-sample of the litter. The number of Oribatida was negatively affected by high soil moisture, whereas the number of Collembola was reduced by the presence of resin. Thus, both factors may contribute to the relatively high number of oribatid mite species and low number of Collembola species in wood ant nests in relation to the numbers in the forest floor.