4.4. Management of the forest landscapes for the Siberian flying squirrel

More than one third of the total number of endangered species in Finland are dependent on forest habitat (Rassi et al. 2000). This being the case, management of biological diversity in forests or even a single forest dwelling species has shown to be a difficult task for conservationists and landscape managers. This is mainly due to a limited knowledge on species ecology, their regional distribution, and local abundances. It is also clear that very detailed guidelining can hardly be provided because landscape patterns and ecological conditions change significantly among regions and, therefore, management recommendations tend to be general by nature. Yet, one has to bear in mind that if there is no long term data on population fluctuation or trends in the region, conclusions concerning practical rules for management have to be drawn with caution. For instance, if a population is declining and management recommendations are based only on one season study, the results may be spurious providing limited use as a sound basis for sustainable management.

This study suggests some general but presumably applicable instructions for forest managers. The main findings emphasise the importance of the landscape structure and context at separate spatial scales as a whole: the entire landscape being a management unit not just single stands as discrete entities (see also Åberg 2000). The use of satellite images enables the visualisation of the spatial dispersion of potential habitat patches for the Siberian flying squirrel and provides an estimate of their quality. Knowledge regarding species ecological requirements and landscape models help to rank habitat patches and, hence, to set preferences for strategic planning. Because of failing to predict the presence of the Siberian flying squirrel accurately, forest stands need to be checked in the field prior to forest cutting. Landscape connectivity can be mapped and likely dispersal routes illustrated. Temporal development of connecting habitat type, which consists often of managed stands, in space can be foreseen from forest stand files. Landscape management can be directed to improve landscape connectivity and forested linkages among habitat patches or to avoid to harvest existing routes. In forest management coarse grain structure should be preferred to subdivision of the remaining old-growth areas into small fragments. These studies propose that a forest landscape where the Siberian flying squirrel persists in northern Finland should contain 20-40 % habitat suitable for dispersal. The spatial arrangement of this habitat is important for landscape connectivity and it should physically bridge spruce dominated forest patches. Proportion of spruce dominated forests is more difficult to estimate due to different classification criteria used in the present studies. Nevertheless, the proportion of this habitat should range from 15 to 20 %. In regions where the Siberian flying squirrel is relatively abundant in northern Finland the amount of deciduous tree rich habitat ranges between 2-4 % (Table 2). Given proportions are always relative to the landscape context in that particular region. This type of study, however, does not provide any unambiguous clue for operative planning as to how to manage deciduous forest sites at stand level in northern Finnish boreal forests. But it suggests that these, often relatively small habitats, should be preserved as key biotopes not only for the Siberian flying squirrel but also because of their overall biodiversity values.