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4. Ecology and History of Forest Use

4.1 European Boreal Forest Ecology

The boreal forest, or taiga, is the world's largest forest biome stretching around the Northern hemisphere in Alaska, Canada, Russia, Fennoscandia, and Scotland. What can be characterized as the European boreal forest is found in Norway, Sweden, Finland, and Russia west of the Ural mountains. Scotland also falls in this boreal zone; however, the vast majority of forests have been converted to agriculture and planted with exotic species and thus has not been included in this inquiry into the European boreal forests. The focus of this inquiry is on Fennoscandia and Northern European Russia. The following section presents a brief background into those unique ecological characteristics of the European taiga, including natural disturbance dynamics, dominant species, and structure, which are important for the existence and maintenance of biodiversity. The changes to the natural forest, in the context of the history of land use, are also presented.

The natural boreal forest can generally be described as a mosaic of upland forests and wetlands with lakes and rivers interspersed. The boreal forests in Fennoscandia and European Russia can be categorized as one distinct subgroup of the European boreal based on the mix of dominant species. This subgroup is characterized by dominant natural coniferous tree species Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) and deciduous species European aspen (Populus tremula) and birch (Betula spp.) (Angelstam 1998). Goat willow (Salix caprea), alder (Alnus spp.), and rowan (Sorbus aucuparia) are also found in the region. Boreal forests are also characterized by a large diversity of dwarf-shrubs, grasses, herbs, mosses, fungi, and lichens (Esseen et al. 1992).

The northernmost part of the boreal region can be characterized as forest-tundra made up of stunted, sparse and swampy forests among tundra and bogs. The main species are Norway spruce (and/or Siberian spruce, Picea obovata, sometimes recognized as a separate species), Scots pine and white birches. To the east, in Arkhangelsk Oblast, vegetation becomes enriched with so-called Siberian species such as Sukaczev larch (Larix sukaczevii), sometimes distinguished from Siberian larch (Larix sibirica) that occurs on the western foothills of the Urals, Siberian fir (Abies sibirica), and Siberian stone pine (Pinus sibirica) (The Forest Encyclopaedia 1986).

The hemiboreal zone, some of which is included in the southwest of the Fennoscandian maps, can be characterized by the presence of temperate broad-leaf species, such as Small-leaved linden (Tilia cordata), ash (Fraxinus excelsior), Wych elm (Ulmus glabra), and Pedunculate oak (Quercus robur) in addition to coniferous trees. Within the region as a whole the boreal zone can be divided into the northern, middle, and southern boreal subsections. In the southern zone scattered presence of the broad-leaf species of the hemiboreal are found. The middle and northern boreal zones are dominated by coniferous trees with birch as the primary broad-leaf species found (Esseen et al. 1992).

Large disturbances created by fires and to a lesser extent insect infestations, as well as gap-phase dynamics found in areas not effected by fire are integral to forest composition, structure, and species composition in the boreal forest. Wildfire is a major natural disturbance factor in the western European boreal forests (Angelstam 1998) as well as in Karelia and Murmansk Oblast. In Arkhangelsk Oblast and Komi the gap-mosaic disturbance pattern is more common.

The disturbance regime of fire creates succession patterns responsible for the mosaic of age classes and species types unique to the boreal forest. Natural wildfire patterns are dependent on a variety of variables. This complexity of variables leads to a wide diversity of impacts, which can be seen in the stand and landscape level diversity of the boreal forest.

Old-growth forest in Panskie Tundry Area (Murmansk Oblast, Russia).
Photo: Konstantin Kobyakov.

The impacts of wildfire on the forest depend on several primary factors: frequency and intensity of the fire, severity, and characteristics of the vegetation. Site factors such as vegetation, slope, elevation, time of the day and year, stand composition, tree species, age class, basal area tree morphology, stand structure, and fire behavior such as fuel moisture, rate of spread, intensity are also vital to understanding the impacts of fire. It is important to note that fire refuges exist in some parts of the forest on moist sites with local humidity, in which fire may be absent for several hundred years (Angelstam 1998). Fire refuges are vital to the forest because many species may survive only in this area to later recolonize in burned areas of the forest.

In forests, in which fire is absent on an ecological time scale of more than 300 years, a gap-phase dynamic pattern is found (Anglestam 1998). In Arkhangelsk Oblast and Komi the gap-phase dynamic is dominant over large areas where fire is not as frequent. The main mechanism providing alternation of generations of trees in these forests is fall of individual trees or their groups because of natural mortality, insects and fungi outbreaks and windfall. Fallen trees create breaks in the canopy allowing light to reach the forest floor and new trees and plant species to grow. The fallen trees also give the forest a supply of dead and decaying wood. New and younger trees in the gap change the environment around them and the composition of plants and wildlife. The appearance of gaps in the forest cover is a random, unpredictable event creating forests of uneven age class and structure (Smirnova et al. 1995; Zakharov et al. 1997; and Yaroshenko 1999).

Tree regeneration on dead wood in an old-growth forest (Russia).
Photo: Alexei Yaroshenko.

Certain boreal species of, for example, certain birds, lichens, and fungi, have particular habitat requirements. The fire regime and gap-phase dynamics of the forest creates a certain set of characteristics on the stand and landscape level creating habitat diversity in the forest, which allows for biodiversity (Angelstam 1998). Important structural components of a natural boreal forest from a species biodiversity standpoint are: very old coniferous and deciduous trees, trees with heavy load of epiphytic lichens, broken top, stag-headed, and leaning trees, trees with holes and cavities, snags, fire-scarred trees, snags and stumps, stumps with uneven surfaces, and large-sized logs in various stages of decomposition (Esseen et al. 1992). Gaps and specific mound-and-depression topography made by windfalls are also important aspects on the landscape level (Smirnova et al. 1995; Zakharov et al. 1997; Yaroshenko 1999).

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