Boreal carabid beetles (Coleoptera, Carabidae) in managed spruce forests – a summary of Finnish case studies

Abstract

Over 90% of the forests in Sweden and Finland are managed (Angelstam 1997, Sevola 1999) and form a mosaic of different successional stages (Hansson 1992). This is a consequence of forestry practices over several centuries, but the most drastic effects of forestry on forest biota have taken place during the past 50 years (Niemela 1999). Over this period of time, the structures of the plant and animal assemblages of boreal forests have been strongly altered (Heliovaara and Vaisanen 1984, Esseen et al. 1992, Niemela 1997). Forestry is responsible for approximately 30% of the Finnish red-listed species being threatened (Rassi et al. 2000). Perhaps the most important reason for this is the fragmentation of old-growth forests. Habitat fragmentation is one of the most important causes of species declines and extinctions across the world (Saunders et al. 1991, Haila et al. 1994, Didham et al. 1996, Didham 1997a, Davies et al. 2000). In southern Finland, roughly 1% of forest cover is protected and only 5% of these are old-growth forests (Virkkala et al. 2000). Protecting all the remaining old-growth forests in these regions is an inadequate measure for the protection of old-growth forest specialists (e.g. Heikkinen et al. 2000). Thus, in addition to protection, the restoration of mature, managed forests and the improvement of the quality of the surrounding managed landscape matrix through the development of appropriate management methods are needed (Niemela 1997, 1999, Nilsson 1997, Monkkonen 1999). Managed forests host fewer threatened forestspecialist species than do old-growth forests, and also many common species occur at low abundance in managed forests. Examples of this difference are e.g. bryophytes and epiphytic lichens (Soderstrom 1988, Andersson and Hytteborn 1991, Kuusinen 1994, 1996, Dettki and Esseen 1998), beetles living in dead wood (Vaisanen et al. 1993, Siitonen and Martikainen 1994, Jonsell et al. 1998) and Mycetophilidae insects (Okland 1994). However, the long-term persistence of many forest species is dependent on populations living in managed forests (Lindenmeyer and Franklin 1997). The maintenance of these populations can possibly be achieved by ecological planning of forestry. Moreover, the importance of ecological forestry planning is not just to maintain old-growth forests but also to prevent the decrease of overall forest biodiversity at the within-stand, regional and national scales.