Indigenous forests versus exotic eucalypt and pine plantations: a comparison of leaf-litter invertebrate communities

Newlands Forest in the Cape Peninsula National Park consists of a patchwork of indigenous forests, eucalypt and pine plantations as well as fynbos vegetation. We compared selected leaf-litter invertebrate taxa (Hymenoptera, Opiliones and Amphipoda) between the two plantation types and indigenous forest using Winkler bag sifted leaf-litter extractions. Species richness was greatest in the indigenous forest (22 species) followed by the eucalypt (19 species) and pine (17 species) plantations. The Incidence-based Coverage Estimator (ICE), which uses the number of rare species in the samples to estimate the potential maximum number of species, estimated 52 species in indigenous forest, 2.4 times richer than the 22 species estimated for pine and 1.8 times richer than the 29 species estimated for eucalypt. The Argentine ant Linepithema humile, (Hymenoptera: Formicidae) was present in all three forest types and may have been one of the causes of the low invertebrate species richness. We recommend that levels of disturbance in the Newlands Forest area be reduced by consolidating the patches of indigenous forest and fynbos.