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Biomes and Regions of Northern Eurasia

Boreal Forests

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European Taiga

The European taiga is mainly composed of the dark taiga species. In the conditions of moist climate and moderate drainage, the main forest-forming species is Picea. The participation of Abies sibirica increases eastwards, where Larix sukaczewii and Pinus sibirica occur in a subordinate role.

The subzone of northern taiga extends from 67°N to 64°N (Figure 9.3).

Fig. 9.3 Vegetation of northern European territories and the Urals. Compiled by A. Tishkov using data from Gribova et al. (1980)

Because of the short and cold summers, with a mean July temperature of about 14°C, tree growth is impeded and although these are closed forests they are not dense. Light penetrates the forest canopy allowing light-requiring plants to develop in the undergrowth. In the west, the main species is Picea abies although large areas, especially in Karelia, are occupied by wetlands and forests composed of Pinus sylvestris. Eastwards, Picea abies is progressively replaced by Picea obovata, which dominates east of the Northern Dvina. Isolated patches of Pinus sylvestris occur on sandy substrata. Siberian species appear with Larix sukaczewii being an important admixture in the north and Abies sibirica in the south. A characteristic of Picea forests of the northern taiga is the ubiquitous presence of green mosses (Hylocomium splendens, Pleurozium schreberi, Polystichum commune) and the admixture of Betula. An unusual association, Picea forests with lichens (Piceetum cladinosum), develops on sandy and stony substrata where canopy cover is low, between 30 per cent and 50 per cent (Agakhanyants, 1986). Productivity of northern forests and phytomass reserves are low, on average 100 tonnes ha -1 (Bazilevich, 1993; Bazilevich and Tishkov, 1986). On the Kola peninsula, where forests develop on stony substrata, and in the Pechora basin, where forests are often swamped, phytomass is reduced to 30-50 tonnes ha^-1. Typical of the northern taiga is a large share of dead phytomass which may reach 30-40 per cent of the total phytomass reserve (Bazilevich, 1993; Bazilevich and Tishkov, 1986).

The middle taiga, which extends from 64°N to 60°N, has a milder climate with a mean July temperature of about 16°C. Two main features distinguish the middle taiga from the northern taiga: forests become notably denser and Betula disappears as an admixture to Picea forests. The main zonal associations are Picea abies (in the west) and Picea obovata (in the east) with Vaccinium myrtillus and green mosses. The undergrowth is virtually absent and the herbaceous cover is depauperate because of the lack of light (Figure 9.4).

Fig. 9.4 Spatial variability in canopy density.

Only shade-tolerant species occur, such as Linnaea borealis, Pyrola rotundifolia, and Calamagrostis. Hilly terrain of the European middle taiga provides a variety of habitats. Pinus sylvestris forests with green mosses develop on sandy substrata in river valleys and on the river terraces Pinus sylvestris with Calluna vulgaris occur. Pine forests constitute over 20 per cent of the middle taiga forests. In the south of the sub-zone, the appearance in azonal habitats of broad-leaved tree species (Tilia cordata and Acer platanoides) in the undergrowth and of Convallaria majalis and Aegopodium podagraria in herbaceous cover add to the diversity of forests. Productivity of forests, phytomass reserves, and the share of wood increases in comparison with the northern taiga. Phytomass reserves in typical Picea forests are about 130 t ha^-1 and productivity is about 6 t ha^-1 a^-1 (Bazilevich, 1993). In contrast to the northern taiga, there is little differentiation in productivity between western, central, and eastern regions.

The southern taiga extends to approximately 57°N. The mean July temperature of about 18°C provides very favourable conditions for the development of forests. Picea forests with Oxalis acetosella replace Picea-Vaccimum myrtittus forests as the main zonal association. The role of mosses is reduced and its share in total phytomass reserve is twice as low as in the northern and middle taiga (Bazilevich, 1993). However, the main distinction from the middle taiga is that the composition of forest becomes more complex as deciduous species become more abundant. The share of wood in total phytomass increases to approximately 75 per cent (Bazilevich, 1993). Forests develop a multitier structure with Tilia cordata, Acer platanoides, Fraxinus excelsior, and Corylus avellana appearing in undergrowth. Where soils are rich and provide enough nutrients, deciduous broad-leaved species (Tilia cordata, Quercus robur, Ulmus laevis, U. scarba) occur in the lower tree tiers. These species are not widespread, the trees grow slowly and are often small. However, it is their presence that distinguishes the southern taiga as a subzone. Herbaceous cover becomes notably richer and species typical of deciduous forest become more common. Pinus sylvestris stands are widespread similarly to the other subzones, and forests composed of Alnus incana become common along the river banks and on abandoned agricultural lands.

In European Russia, the middle and especially the southern taiga have been transformed by human activities. This is one of the major timber-producing regions of the FSU and in the localities where spruce stands have been cut, secondary forests composed of Betula and Populus tremula develop. Alnus incana also spread into the southern taiga only recently due to human influence, being almost unknown in the region three to five centuries ago.

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