Habitat fragmentation

Urban uses often lead to the fragmentation of woodlands and to stark divi­sions within stands through intended and unintended paths and horseback­riding trails as well as roads. In this way, small woodland patches with high edge-to-interior ratios are created. Forest fragmentation generally en­hances pioneer species or non-native species that respond well to an in­creased availability of light (Brothers and Spingarn 1992; Godefroid and Koedam 2003a). Fragmentation by roads supports species that are dis­persed by vehicles (Parendes et al. 2000; Ebrecht and Schmidt 2003). However, typical forest plant species, including rare species, may also oc­cur along forest edges (Godefroid and Koedam 2003b). Bird species are often negatively affected by decreasing patch size (e. g. Mortberg 2001). An increasing density of paths can negatively affect the establishment of saplings (Lehvavirta and Rita 2002), but the regeneration of trees is gener­ally not threatened in urban woodlands. Due to varying responses of tree species to fragmentation, changes in the species composition, however, may occur. The ground layer is most susceptible to trampling, which leads to a decrease in the vegetation cover (Malmivaara et al. 2002).