Ants are often considered as good indicators of change of management in different habitats. They have been used sporadically to evaluate large scale transformations involving reafforestation. In the present study, the ant assemblages at 15 forest sites are compared. The sites differ in history, age and forest management. Our results show that there are clear changes in ant assemblages with developmental stage but even after 25 years not all forest species are present. Natural succession and planting of trees with or without any other management, resulted in only open country species, and some from forest and wet grassland colonizing these new forests. Sometimes gynes of target forest species arrived in new forests from nearby mature forest, but apparently were unable to start a colony. We attribute this findings to the lack of appropriate vegetation structure and litter characteristics, which determines the forest ant fauna, more than the dispersal of ant gynes. Further investigations should enable us to predict if these conditions can be produced by 50-100 or more years of forest succession and adequate management.
The number of colonies of red wood ants (Formica rufa group) in the north western part of Belgium has declined by more than half over the past 20 years. In the study area of 20 × 50 km there are currently only 36 colonies of two species of red wood ants (Formica rufa and F. polyctena). Both species form both monodomous and polydomous colonies. Monodomous F. rufa colonies occur in large areas of open woodland dominated by Pinus sylvestris. The other three types of red wood ant (F. rufa polydomous, F. polyctena mono- and polydomous) occur in clearings or along the margins of small areas of deciduous or mixed woodland. The extinction of red wood ants cannot be attributed to a loss of their main habitat. Their decline in abundance, however, appears to be due to the deterioration in their habitat caused by several factors. Shading by overgrowing shrubs and the closure of the tree canopy, nearby intensive agriculture, urbanisation and use of the forest for recreation are the more important factors threatening and ultimately leading to the extinction of colonies. At poor quality sites there are no or very few nests of Serviformica ants, which initially serve as host ants and are necessary for recolonization by red wood ants. Thus, it is unlikely that these sites will be recolonized. To conserve red wood ants and maintain populations there is an urgent need to undertake certain measures, especially in areas outside nature reserves. For this there is a need to create clearings in the woodland, reduce shading due to overgrowing shrubs and closure of the tree canopy, and mitigate the effects of intensive agriculture, urbanisation and recreation. It is important that the effects of these measures should be monitored.