Ant communities in fragments of old-growth taiga and managed surroundings

The structure of ant communities was studied by sampling with pitfall traps in 24 mixed coniferous old-growth fragments (>140 yrs old), their edges, and managed surroundings of different ages in southern Finland. The old-forest ant community consisted of only three common shade-tolerant species, Formica aquilonia, Myrmica ruginodis and Camponotus herculeanus, whereas most of the ant species inhabited the early stages of forest succession. The size of the fragment affected only slightly the ant community. The most common territorial wood ant, F. aquilonia, structured the ant community by suppressing other species, although not equally so. The ant-community structure in the context of forest succession and landscape structure is discussed, and the successions in managed forests compared to those occurring after more natural disturbances. Forestry has changed the dynamics of succession and structural characteristics of the forest stands. Important changes of the landscape affecting forest-ant species are age-distribution of the forests and the fragmentation of old-growth forests accompanied by an increased proportion of edge habitats: open-country species have gained a greater inhabitable area and the relative abundances of the territorial wood-ant species (Formica s. str.) have changed. The multinest supercolonies of F. aquilonia have decreased, whereas species such as F. lugubris, which in our study area tend to be monodomous, have benefitted.