The community structures and seasonal changes of soil microarthropods in a natural sessile oak (Quercus petraea L.) stand and an adjacent Scots pine (Pinus sylvestris L.) plantation in Belgrad Forest, Istanbul, Turkey were investigated between November 2008 and October 2009. Microarthropods were sampled monthly, using steel soil corers. The mean annual abundances of microarthropods were 42,851 individuals m(-2) in the oak stand and 42,276 individuals m(-2) in the Scots pine plantation. The Shannon diversity index (H') of microarthropods in the Scots pine stand was 9.6% higher (p<0.05) than those of the native oak stand. Although conversion of a sessile oak stand to a Scots pine plantation did not impact the abundance of soil microarthropods, it increased their diversity.