Urban Forestry & Urban Greening 13 (2014) 869–877 Contents lists available at ScienceDirect Urban Forestry & Urban Greening journal homepage: www.elsevier.com/locate/ufug Fragmentation and recreational use affect tree regeneration in urban forests Susanna Lehvävirta a,b,∗ , Ferenc Vilisics b , Leena Hamberg c , Minna Malmivaara-Lämsä c , D. Johan Kotze b a Botanic Garden and Herbarium, Finnish Museum of Natural History, University of Helsinki, PO Box 7, FI-00014 Helsinki, Finland b Department of Environmental Sciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland c Finnish Forest Research Institute, PO Box 18, FI-01301 Vantaa, Finland article info Keywords: Boreal forest Edge effects Forest dynamics Recreation ecology Spatial structure Tree saplings abstract The aim of this study was to test whether fragmentation or recreational use affect tree regeneration in urban forests, and to quantify these effects. We sampled tree saplings at different distances from edges in spruce (Picea abies) dominated forests, and at different distances from paths that represented differ- ent levels of wear. Generalized linear mixed models were used to test our hypotheses. We found that fragmentation favours the regeneration of deciduous trees in urban spruce dominated forests: distance from the edge had a pronounced effect on regeneration, at least up to 80 m into the forests. Saplings of Betula pendula, Populus tremula, other deciduous species and Pinus sylvestris benefited from edge condi- tions. Betula pubescens saplings, however, were most abundant in the interior and small Sorbus aucuparia saplings at 25–30 m from the edge. All species suffered from the direct effects of trampling, while vary- ing responses of species to distance from the paths were observed up to 6 m, and possibly further. As trees essentially define the living conditions for other forest species, we suggest that the spatial extent of edge and trampling effects should be studied for different types of forests. This knowledge should then be used in urban forestry and planning to define the threshold value that will allow for at least some “intact” interior. We suggest a diameter larger than 160 m to support indigenous species in boreal spruce dominated forests. © 2014 Elsevier GmbH. All rights reserved. Introduction It has been argued that natural regeneration dynamics should be allowed in urban forests (Greene et al., 1999; Lehvävirta, 2007), thus not only saving in management costs but also enhancing possibilities for education, research, biodiversity and recreational value, amongst others. In urban environments, however, natu- ral dynamics are altered, which may affect the regeneration of trees (Tonnesen and Ebersole, 1997; Lehvävirta and Rita, 2002; Malmivaara-Lämsä et al., 2008b; Hamberg et al., 2009a). For exam- ple, urban forests are usually drier and sunnier due to their small size (DeWalle and McGuire, 1973; Matlack and Litvaitis, 1999), with an increase in temperature and soil nutrient content (Hamberg ∗ Corresponding author at: Botanic Garden and Herbarium, Finnish Museum of Natural History, University of Helsinki, PO Box 7, FI-00014 Helsinki, Finland. Tel.: +358 50 5762952. E-mail addresses: susanna.lehvavirta@helsinki.fi (S. Lehvävirta), vilisics.ferenc@gmail.com (F. Vilisics), leena.hamberg@metla.fi (L. Hamberg), malmivaa@gmail.com (M. Malmivaara-Lämsä), johan.kotze@helsinki.fi (D.J. Kotze). et al., 2009b; O’Brien et al., 2012). This may favour drought- and heat tolerant species and those benefiting from high nutrient lev- els. In addition, urban forests are characterised by continuous and repeated anthropogenic factors. In this study we focus on trampling and fragmentation, as evidence suggests they are good candidates for scientific hypotheses about factors affecting tree regeneration in urban forest. Understanding their effects may essentially help in the successful planning and management of these forests. Fragmentation increases the proportion of edges resulting in smaller areas for forest interior conditions and consequent changes in vegetation (Bannerman, 1998; Hamberg et al., 2008, 2010; Vallet et al., 2010; Ranta et al., 2013). Forest edges experience high vari- ation in daily temperature, decreased moisture and increased air particle levels due to solar radiation and wind (e.g. Chen et al., 1995; Bannerman, 1998; Weathers et al., 2001; Malmivaara-Lämsä et al., 2008a). Trampling in turn disturbs the forest floor and tree regeneration (Lehvävirta, 1999; Hamberg et al., 2008, 2010; Hauru et al., 2012). Residents use urban forests for a variety of activities, such as recreation, exercise, play and shortcuts, thus creating exten- sive path networks, reducing plant cover, and damaging tree roots http://dx.doi.org/10.1016/j.ufug.2014.10.003 1618-8667/© 2014 Elsevier GmbH. All rights reserved.