Сосновые (Pinus sylvestris) леса и редколесья Северо-Западного Приладожья

Abstract

Ladoga is the largest lake in Europe (with 17 870 km2 area, 838 km3 water volume, and 47/230 m average/maximum depths), it lies around connection of two large geological structures: the Baltic crystal Shield and Russian Platform (Isachenko, Reznikov 1996). The climate is characterized by frequent fronts of the Baltic, White and Barents seas, and prevalence of intensive cyclonic activity the whole year around. The Ladoga lake influences on the adjacent territories making climate smoother near its shores; the Karelian coast is characterized by soft winter, and longer vegetative and unfrosted periods (Ladoga…, 2000). In conformity to L. E. Nazarova (Nazarova, 2006), the annual atmosphere temperature has increased on 1.1–1.3 °С within 50 years (1951–2000) in this region. The study territory of North-Western Ladoga region is located in the southern area of the Baltic Crystaline Shield granite rock outcrops. The field researches were carry out on a key-site (35 km2) with the aim compile a large-scale vegetation map (M. 1 : 25 000). Landscape is heterogenic with rocks (granite and granodiarite, limnetic clay, pet) and complex relief (tops, slopes and foots of selgas, limnetic terraces and narrow selga depressions). The most easily reached sites of terraces and bogs were actively used as agricultural lands (up to 1940th by Finns, later on by Russians). The region is situated in taiga belt. Spruce, pine and small-leaved forests prevail in the study area, while meadows and bogs are less common. The most widespread are forests and woodlands with dominant Pinus sylvestris. The vegetation was described by methods according to principles of ecological-phytocoenotic classification (Gribova, Isachenko, 1972; Neshataev, 1987; Vasilevich, 1995; Methods ..., 2002). 93 relevés were performed on sample plots of 400 m2 or within the community boundaries. The following characteristics were taken into account: density, height and diameter of trees, composition and grass-shrub and moss-lichen layer cover (in percents). In pine forest shares of Pinus sylvestris (the number of trunks) are >5 units (in 10-point scale); sparse low-tree pine communities on rocks with tree density of less then 0.3 were classified as woodlands. Associations are distinguished according the species dominance in the herb layer and the combination of ecological-phytocoenotic groups. There are 5 groups of associations (Pineta cladinosa, Pineta hylocomiosa, Pineta nemoriherbosa, Pineta paludosa, Pineta sphagnosa), 12 associations and 11 variants established according to ecological-phytocoenotic classification. Forest and woodland assosiations of Pinus sylvestris of the NW Ladoga region: Pinetum cladinosum saxatilis (Table 1; Table 7, syntaxa 1–3; Fig. 2); Pinetum fruticulosum saxatilis (Table 2, relevés 1–9; Table 7, syntaxon 4); Pinetum vacciniosum (Table 2, relevés 10–12; Table 7, syntaxon 5; Fig. 4); Pinetum myrtillosum (Table 3, relevés 1–19; Table 7, syntaxa 6–8; Fig. 5а, б); Pinetum myrtilloso–calamagrostidosum (Table 4, relevés 1–14; Table 7, syntaxa 9, 10); Pinetum calamagrostidoso–herbosum (Table 4, relevés 15–19; Table 7, syntaxon 11); Pinetum myrtilloso-oxalidosum (Table 5, relevés 1–7; Table 7, syntaxa 12–14); Pinetum oxalidosо–equisetosum (Table 5, relevés 8–12; Table 7, syntaxon 15; Fig. 6а, б); Pinetum nemoriherbosum (Table 5, relevés 13–16; Table 7, syntaxon 16; Fig. 7а, б); Pinetum filipendulosum (Table 5, relevés 17–18; Table 7, syntaxon 17), Pinetum fruticuloso–hylocomioso–sphagnosum (Table 6, relevés 1–3; Table 7, syntaxon 18; Fig. 8); Pinetum myrtilloso–sphagnosum (Table 6, relevés 4–5; Table 7, syntaxon 19). Tops of the granite hills (selgas) are rocky coverd by frost resistent communities on primitive litogenic soils, where snow cover is blown off in winter. Common are communities of the ass. Pinetum cladinosum saxatilis with sparse and undersized Pinus sylvestris, unclosed lichen and greenmoss cover (Arctoparmelia centrifuga, Umbilicaria sp., Cladonia arbuscula, C. rangiferina, C. stellaris, C. uncialis s. str., Dicranum polysetum, D. scoparium, Pohlia nutans, Polytrichum juniperinum, Pleurozium schreberi) and woodlands of the ass. Pinetum cladinosum saxatilis var. callunosum (Calluna vulgaris, species of genera Cladonia, Dicranum polysetum, Pleurozium schreberi, Polytrichum juniperinum). Primitive litogenic soils are formed at gently tops and near-top slopes with forests of the ass. Pinetum fruticulosum saxatilis with some lichen. Mid parts of selga slopes are occupied by different types on the “podbur” soil (similar to thin mountain taiga soil). The selga slopes are usually covered by forests of the ass. Pinetum myrtilloso–calamagrostidosum (Calamagrostis arundinacea, Vaccinium myrtillus) and ass. Pinetum myrtilloso–oxalidosum (Oxalis acetosella, Vaccinium myrtillus) with an admixture of small-leaved trees. The gentle slopes and bottom parts of selga slopes are occupied phytocenoses of the ass. Pinetum calamagrostidoso–herbosum with heliophilous subnemoral herbal species (Convallaria majalis, Fragaria vesca, Hepatica nobilis, Geranium sylvaticum, Rubus saxatilis, Pteridium aquilinum, Veronica chamaedrys, Viola canina) and mosses (Pleurozium schreberi, Dicranum polysetum, Hylocomium splendens, Rhytidiadelphus triquetrus). The selga depressions are occupied by phytocenoses of the associations Pinetum fruticuloso–hylocomioso–sphagnosum and Pinetum myrtilloso–sphagnosum. The lake terraces were used by Finns (up to 1944) as agricultural grounds (meadows, pastures, arable lands). After the end of cultivation the young grey alder groves with mesophytes (Aegopodium podagraria, Geum rivale) and hygromesophytes (Filipendula ulmaria, Lysimachia vulgaris, Scirpus sylvaticus) have became the most typical element of postagricultural lands where shade-requiring boreal and nemoral species gradualy were being replaced by heliophilous meadow plants (Veremeeva, 2004). The next succession stage is the appearance and growth of coniferous trees. Pine forests from the Pineta nemoriherbosa and Pineta paludosa groups on cultivated lake terraces are rather young (40–70 years). According to classification of G. A. Isachenko (Isachenko, 1996), such forests belong to the final (4th) succession stage of agricultural land with tree species before the restoration of coniferous forests. Also, ecotope conditions (soil richness, sufficient humidifying) promote increase the cover of nemoral (Aegopodium podagraria, Hepatica nobilis, Pulmonaria obscura, Milium effusum), hygromesophylous and hygrophylous herbs (Filipendula ulmaria, Athyrium filix-femina, Equisetum sylvaticum, Geum rivale, Oxalis acetosella, Deschampsia cespitosa). The presence of spruce in the tree stand, the abundance of Oxalis acetosella, nemoral and hygrophytic herbs shows that these forests of the associations Pinetum oxalidosо–еquisetosum, Pinetum nemoriherbosum and Pinetum filipendulosum when they are not affected by anthropogenic impacts may be restored to forests of the associations Piceetum oxalidosо–еquisetosum, Piceetum nemoriherbosum and Piceetum filipendulosum.