RESEARCH ARTICLE Effects of Retention Felling on Epixylic Species in Boreal Spruce Forests in Southern Finland Harri Hautala, 1,4 Sanna Laaka-Lindberg, 2,3 and Ilkka Vanha-Majamaa 1 Abstract We studied the effects of patch retention felling and soil scarification by harrowing on the coverage and species richness of epixylic species in boreal Norway spruce (Picea abies ) forests in Southern Finland. The epixylics were investigated from both the retention tree groups (RTGs) and the surrounding felling areas before and after fellings and after scarification on consecutive years. The cover percentage of all included species groups was shown to decrease after the felling, especially in the felling areas (vas- cular plants, -0.4%; mosses, -27.8%; liverworts, -4.0%; and lichens,-2.1%). The decrease was considerable also in the RTGs. The amount of dead moss increased in both the areas indicating microclimatic changes. Species rich- ness also declined rapidly after the first year, especially in the felling areas (vascular plants, -2.2%; mosses, -27.3%; liverworts, -30.3%; and lichens, -22.9%). Scarification also decreases covers and species richness of bryophytes. After the second year, the covers of the species groups gen- erally started to regain, especially in the untreated RTGs. The size of RTG was in positive correlation with the total species number. Another main result indicates that it is possible to maintain much higher initial vegetation abun- dance and diversity in the RTGs than in the felling areas. Coarse woody debris formed by the frequent tree uproot- ings may also enhance the long-term survival of epixylics over forest regeneration period. RTGs should be at least 10 times larger than the size used in current Finnish forestry, so that they could function as species refugia. Key words: bryophytes, coarse woody debris, epixylic, lichens, variable retention, vascular plants. Introduction Coarse woody debris (CWD) a is a crucial element for the existence of many organisms in the boreal forests. According to Siitonen (2001), 20–25% of the forest species in Finland are dependent on the availability of dead wood. During the decades of intensive forestry from 1950s to the present day, amount of CWD in Finnish forests has decreased notably because of the extensive forest management practices, such as thinning of stands and removal of CWD, which have led to large-scale impoverishment of forest biodiversity (Anony- mous 2000). The average amount of dead wood in heavily managed forests of Southern Finland is currently less than 3m −3 /ha (Anonymous 2006), whereas the amount of CWD in unmanaged forests of the same area can reach over 100 m −3 /ha (Siitonen et al. 2000). Because the regeneration phase takes several decades in boreal forests, it is essential to ensure the continuum and 1 The Finnish Forest Research Institute, Vantaa Research Unit, PO Box 18, FIN-01301 Vantaa, Finland 2 Lammi Biological Station, University of Helsinki, FIN-16900 Lammi, Finland 3 Botanical Museum, PO Box 7, FIN-00014 University of Helsinki, Finland 4 Address correspondence to H. Hautala, email harri.hautala@metla.fi a Downed woody material with diameter >10 cm logs throughout this paper (see Lofroth [1998] for the definition of CWD).  2009 Society for Ecological Restoration International doi: 10.1111/j.1526-100X.2009.00545.x dispersal chances of epixylic b species over the forest regen- eration period. Because CWD is crucial substrate for many species of bryophytes and even for some vascular plants (Lofroth 1998), both qualitative and quantitative continuum of CWD are required for the species survival. Under currently practiced forest management methods in Finland, a significant volume of CWD is being destroyed because of scarification by harrowing (Hautala et al. 2004), which is commonly used as a soil preparation method in order to enhance the seedling establishment of trees. Scarification affects especially the highly decayed decid- uous logs that are considered the most valuable for biodi- versity (Andersson & Hytteborn 1991; Hautala et al. 2004). The epixylic bryophytes are especially sensitive, because the species are dependent on the continuum of certain type of CWD (Esseen et al. 1997; Kushnevskaya et al. 2007). For example, 20% of the threatened liverworts in Finland demand biotopes with high amount of CWD, but the continuum of CWD in Finland is not adequate (Rassi et al. 2001). Ander- sson and Hytteborn (1991) observed that the high amount and diversity of CWD is correlated with the number of epixylic bryophyte species. In Southern Sweden, presence of woody substrates explained 30% of the occurrence of red- listed bryophytes and fungi (Berg et al. 2002). CWD may also b Species that use (dead) wood as their nesting/breeding site or for some other critical functions during their life cycle (definition of Stokland, 2007). 418 Restoration Ecology Vol. 19, No. 3, pp. 418–429 MAY 2011