CLASSIFICATION OF FORESTS USING A FIELD GUIDE OF FOREST TYPES OF THE EUROPEAN RUSSIA (EVIDENCE FROM KARELIA AND THE KARELIAN ISTHMUS)

Classification of forests of Karelia and the Karelian Isthmus was carried out using the field guide of the forest types of the European Russia developed by L. B. Zaugolnova and V. B. Martynenko. The studied forests were divided into five main sections: lichenous, green moss, sphagnous, grass and grassmarsh. The most common sections were the green moss and the sphagnous one. They include five groups of forest types each. The least diverse is the lichenous section: it consists of only two groups of forest types. In each group of forest types individual forest types were identified. The most common types of forest were bilberry-green moss pine and spruce forests.

Beta diversity is indicative of the variability of alpha diversity indicators in space during the transition from one type of forest to another. Beta diversity was estimated using the similarity index (Jaccard index) and the heterogeneity index (Whittaker index). In addition to these indices, vegetation beta diversity can be characterized by the set and number of forest types represented in a particular area.

RESULTS AND DISCUSSION
According to the geobotanical descriptions of the PLPs, the studied forests of the northern and middle taiga can be divided into 5 main sections depending on the general coverage of the moss-lichen layer and the ratio of lichens, green and sphagnum mosses in its composition: lichenous section (cladinosa), green moss section (hylocomiosa), sphagnous section (sphagnosa), grass section (herbosa), grass and marsh section (uliginosoherbosa). Let us have a more detailed look at them.
dominating therein. Due to the formation of leaf litter, the moss cover can fall to 40% and less, such communities are a transitional form between the green moss and grass sections. The grass-dwarf shrub layer consists mainly of boreal species: Vaccinium myrtillus, V. vitis-idaea, V. uliginosum, Empetrum hermaphroditum, E. nigrum, Linnaea borealis, etc. At the same time, species of the Empetrum genus are most often found in the forests of the northern taiga.
The green moss section includes forests of five groups of forest types: dwarf shrub-green moss birch forests, small grass-green moss spruce forests, dwarf shrub-green moss spruce forests, dwarf shrub-green moss pine forests and small grass-green moss pine forests (Fig. 3). The most common group of forest types is the group of dwarf shrub-green moss pine forests. They occupy about 50% of the PLPs belonging to the green moss section. The second most common group includes dwarf shrub-green moss spruce forests (about 30% of the PLPs of the green moss section).
The share of small grass-green moss spruce and pine forests as well as dwarf shrub-green moss birch forests is approximately the same. Let us consider the groups of forest types of the green moss section.

Figure 3.
Ratio of PLPs by forest type groups. Green moss section. The X-axis shows groups of forest types (1dwarf shrub-green moss pine forests, 2dwarf shrub-green moss spruce forests, 3 small grass-green moss spruce forests, 4small grass-green moss pine forests, 5dwarf shrubgreen moss birch forests), the Y-axis shows the percentage Dwarf shrub-green moss pine forests are the forests where the tree layer is dominated by Pinus sylvestris (geobotanical descriptionsee Table 1) with Betula pendula, B. pubescens, Picea abies, etc. as common admixtures (Fig. 4). Within the dwarf shrub-green moss pine forest group of forest types five forest types are identified: bilberry-green moss pine forests, cowberry-green moss pine forests, cowberry-heathergreen moss pine forests, bilberry-ledum-green moss pine forests, and heathberry-bilberry-green ______________________________________________________________________________________________ Forest Science Issues, Vol. 2 (2), 2019 moss pine forests. Of those, bilberry-green moss pine forests are predominant, with approximately the same share in the northern and middle taiga (Fig. 5). The northern taiga has two types of forests that are not found in the middle taiga: bilberry-ledum-green moss and heathberry-bilberry-green moss pine forests.
Dwarf shrub-green moss pine forests are almost ubiquitous and are very common in the northern and middle taiga. These forests usually result from repetitive fires. If there are no fires for a long time, the forests turn into pine stands with a large share of spruce, and laterinto spruce forests with singular pine trees.

Figure 5.
The ratio of forest types in the group of dwarf shrub-green moss pine forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The X-axis shows forest types (1bilberry-green moss pine forests, 2cowberry-green moss pine forests, 3cowberry-heather-green moss pine forests, 4bilberry-ledum-green moss pine forests, 5heathberry-bilberry-green moss pine forests), the Y-axis shows the percentage Small grass-green moss pine forests were seen only in PLPs located in the forests of the middle taiga (geobotanical descriptionsee Two forest types are subdivided within the group of dwarf shrub-green moss pine forests: bilberry-oxalis-green moss pine forests (8 PLPs) and hair grass-bracken-green moss pine forests (1 PLP).
Small grass-green moss pine forests grow on flat parts and slopes of lake terraces, on the slopes of the dividing ridge on the outwash sandy loam or sandy moraine.  1.6 28.6 18.6 7.9 Total projective cover of the grass layer (C), % 15.6 81.1 59.0 20.8 Total projective cover of the moss-lichen layer (D), % 0.9 31.4 11.1 11.2 Total projective cover of green mosses in the moss-lichen layer, % 0.9 31.3 9.7 11.3 Total projective cover of lichens in the moss-lichen layer, % 0.0 0.5 0.1 0.2 Total projective cover of sphagnum mosses in the moss-lichen layer, % 0.0 11.8 1.4 3.9 Number of PLPs 9 Comment. Legendsee Table 1. Dwarf shrub-green moss spruce forests (geobotanical descriptionsee Table. 3). Picea abies is dominating in the tree layer with the admixture of Betula pubescens (Fig. 6) Microdepressions are home to some species of Sphagnum genus. The share of lichens within this layer is small.
Three types of forests are subdivided within the group of dwarf shrub-green moss spruce forests: bilberry-green moss spruce forests, cowberry-green moss spruce forests and dwarf shrubgreen moss spruce forests. Of those, bilberry-green moss spruce forests are predominant, most often to be seen in the middle taiga (Fig. 7). Dwarf shrub-green moss spruce forests are virtually ubiquitous and rather common in the northern and middle taiga. Both spruce and pine forests often have post-fire origin.
Small grass-green moss spruce forests (geobotanical descriptionsee Table 4). In the entire network of PLPs located both in the northern and middle taiga this group of forest types was found on ten plots: one in the forests of the northern taiga and ninein the middle taiga. The tree layer is formed by Picea abies with a small admixture of Betula pubescens, B. pendula, Pinus sylvestris, and less frequently -Alnus incana (Fig. 8). A mixed tree layer of Picea abies and Pinus sylvestris may occasionally be formed. In this case, the structure and composition of lower layers  The ratio of forest types in the group of dwarf shrub-green moss spruce forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The Xaxis shows forest types (1bilberry-green moss spruce forests, 2-cowberry-green moss spruce forests, 3dwarf shrub-green moss spruce forests), the Y-axis shows the percentage Dwarf shrub-green moss spruce forests are virtually ubiquitous and rather common in the northern and middle taiga. Both spruce and pine forests often are of post-fire origin.
Small grass-green moss spruce forests (geobotanical descriptionsee Table 4). In the entire network of PLPs located both in the northern and middle taiga this group of forest types was found on ten plots: one in the forests of the northern taiga and ninein the middle taiga. Microdepressions are home to some species of Sphagnum genus. The share of lichens in the composition of the layer is insignificant. fern-green moss spruce forests. Of these, bilberry-small grass-green moss spruce forests dominate, being common in the middle taiga ( Fig. 9).   Small grass-green moss spruce forests often grow on drained habitats; they can be found on the slopes of moraine hills, on flat sections of dividing ridges, on the smooth slopes of the foothills ______________________________________________________________________________________________ Forest Science Issues, Vol. 2 (2), 2019 on both noncalcareous and calcareous moraine loams. This group of forest types has traditionally been regarded as representing zonal vegetation of the middle taiga; these forests, having higher floristic diversity differ from dwarf shrub-green moss spruce forests. Table 5). The forest stand is formed by Betula pubescens with a small admixture of B. pendula, Pinus sylvestris and Picea abies (Fig. 10). The layer of understorey of trees and shrubs consists mainly of Picea abies.  . The ratio of forest types in the group of small grass-green moss spruce forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The Xaxis shows forest types (1bilberry-small grass-green moss spruce forest, 2oxalis-fern spruce forest, 3small fern-green moss spruce forest), the Y-axis shows the percentage Two forest types are subdivided within the group of dwarf shrub-green moss birch forests:

Dwarf shrub-green moss birch forests (geobotanical descriptionsee
dwarf shrub-green moss birch forests and bilberry-green moss birch forests. The first forest type is found in the forests of the northern taiga, and the latter onein the middle taiga (Fig. 11).  . The X-axis shows forest types groups (1dwarf shrub-green moss birch forests, 2dwarf shrub-green moss spruce forests, 3small grass-green moss spruce forests, 4dwarf shrub-green moss pine forests, 5small grass-green moss pine forests), the Y-axis shows the number of plant species (vascular plants, mosses, lichens) Floristic diversity of the forests of the green moss section was estimated using alpha and beta diversity.
Evaluation of alpha diversity. Species density in different forest type groups of the green moss section varies within a rather broad rangefrom 24 to 47 species (Fig. 12). At the same time the majority of PLPs were found to have 20 to 40 plant species (Tables 6-10). The highest floristic diversity is typical for small grass-green moss pine and spruce forests: up to 80 plant species per PLP. Such forests represent more advanced stages of succession (Morozova et al., 2008). Dwarf shrub-green moss pine forests are the poorest in species density, as most often they result from repetitive fires. The number of plant species per PLP in such forests rarely exceeds 20. Species richness depends primarily on the number of PLPs belonging to a certain group of forest types, but generally it correlates with species density.
Evaluation of beta diversity. Beta diversity (Tables 11 and 12) within the green moss section is assessed using Jaccard index and Whittaker index. At pair-wise comparison of forest type groups of the green moss section Jaccard similarity index varies in the range from 0.2 to 0.6. Dwarf shrub-green moss pine and spruce forests demonstrate the biggest similarity (0.6), so do small grass-green moss pine and spruce forests (0.6); the lowest similarity is found between dwarf shrubgreen moss birch forests and small grass-green moss spruce forests (0.2). The value of Whittaker's index (10.2) here is significantly higher than for different groups of forest types within the section (2.7-5.9).  Comment. Legendsee Table 6.  (Zaugolnova, Morozova, 2004).  Table 6.
БКЗdwarf shrub-green moss birch forests, ЕКЗdwarf shrub-green moss spruce forests, ЕМЗsmall grass-green moss spruce forests, СКЗdwarf shrub-green moss pine forests, СМЗsmall grass-green moss pine forests. 2.7 5.7 3.9 5.9 3.1 10.2 Comment. БКЗdwarf shrub-green moss birch forests, ЕКЗdwarf shrub-green moss spruce forests, ЕМЗsmall grass-green moss spruce forests, СКЗdwarf shrub-green moss pine forests, СМЗsmall grass-green moss pine forests. The forests of the green moss section are very common both in the northern and the middle taiga. They are mostly various monodominant pine forests with a relatively high tree canopy density, the predominance of one or two types of dominants in the grass-dwarf shrub layer, and well-developed moss cover of boreal green mosses. In the long-term absence of fires or felling, spruce understorey can enter the tree layer, and pine forests with spruce are replaced by spruce forests with singular pine trees. At the same time, spruce forests quite often demonstrate post-fire origin as well (Volkov, 2008;Zaugolnova, Morozova, 2004). Birch forests usually represent a postfire or post-felling derivative version of pine and spruce forests of this section, which is proven by the floristic similarity of these forests.

Lichenous section (cladinosa)
Classification and characteristics of forests. Communities of the lichenous section are not common in the studied forests: of all the established PLPs only 8% belong to the lichenous section.
The majority of them was found in the forests of the northern taiga. They are different pine forests with a well-developed moss-lichen cover: as a rule, the coverage of the layer is at least 50%. The lichen coverage exceeds or is almost equal to that of mosses.
Only two forest types groups are represented in the lichenous section: lichen pine forests and lichen-green moss pine forests. Their share is equal. Let us look at the groups of forest types of the lichenous section.

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Lichen pine forests (geobotanical descriptionsee Table 13) were found only in the forests of the northern taiga. The tree layer is dominated by Pinus sylvestris with a small admixture of Betula pubescens (Fig. 14).   Three types of forests are subdivided within the group of lichen pine forests: heather-lichen pine forests, heathberry-cowberry-lichen pine forests and cowberry-lichen pine forests, with the domination of the heather-lichen pine forests (Fig. 15). Figure 15. The ratio of forest types in the group of lichen pine forests. The shaded columns stand for the northern taiga. The X-axis shows forest types (1-heather-lichen pine forests, 2heathberrycowberry-lichen pine forests, 3cowberry-lichen pine forests), the Y-axis shows the percentage Green moss-lichen pine forests (geobotanical descriptionsee Table 14). The tree layer consists of Pinus sylvestris with a small admixture of Betula pubescens and Picea abies. The shrubs layer and the understorey are relatively poorly developed (Fig. 16) Three types of forests are subdivided within the group of green moss-lichen pine forests: green moss-lichen heather pine forests, green moss-lichen bilberry pine forests, and green mosslichen cowberry pine forests. There are only a few PLPs for each forest type. Predominant forests are green moss-lichen heather pine forests, which are found both in the northern (2 PLPs) and middle (1 PLP) taiga (Fig. 17).  Comment. Legendsee Table 13.       The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The X-axis shows groups of forest types (1long-stem moss-sphagnum spruce forests, 2dwarf shrub-sphagnum pine forests, 3long-stem moss-sphagnum pine forests, 4long-stem moss-sphagnum birch forests,5eumesotrophic grass-sphagnum spruce forests), the Y-axis shows percentage The sphagnous section includes the forests belonging to five groups of forest types: longstem moss-sphagnum birch forests, dwarf shrub-sphagnum pine forests, long-stem moss-sphagnum pine forests, long-stem moss-sphagnum spruce forests, and eumesotrophic grass-sphagnum spruce forests. Among the listed groups of forest types the most common are long-stem moss-sphagnum spruce forests (Fig. 20). They account for about 50% of the PLPs belonging to the sphagnous section. The second most common are dwarf shrub-sphagnum pine forests and long-stem moss-

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A.V. Gornov 28/49 sphagnum pine forests. The share of long-stem moss-sphagnum birch forests and eumesotrophic grass-sphagnum spruce forests is insignificant. Let us consider the groups of forest types of the sphagnous section. Table 19). Picea abies dominates in the tree layer, Betula pubescens, Pinus sylvestris, etc. can be found as an admixture (Fig. 21) (Korchagin, 1940). It is associated with fires: after the trees death, evaporation drops dramatically, and the development of the haircap moss-based coverage further deteriorates of the hydrological regime. Two types of forest are subdivided within the group of long stem moss-sphagnum spruce forests: bilberry-sphagnum spruce forests and bilberry-long stem moss-sphagnum spruce forests (Fig. 22). Predominant are the bilberry-long-stem moss-sphagnum spruce forests, which are found only in the middle taiga.

Long-stem moss-sphagnum spruce forests (geobotanical descriptionsee
Long stem moss-sphagnum spruce forests grow on the flat depressions between the ridges in floodplain landscapes as well as in the heads of small rivers and mesorelief depressions. Long-stem-sphagnum pine forests (geobotanical descriptionsee Table 20)    . The ratio of forest types in the group of long-stem moss-sphagnum spruce forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The Xaxis shows forest types (1bilberry-long-stem moss-sphagnum spruce forests, 2bilberrysphagnum spruce forests), the Y-axis shows the percentage Figure 23. The ratio of forest types in the group of long-stem moss-sphagnum pine forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The Xline shows forest types (1bilberry-sphagnum pine forests, 2cloudberry-sphagnum pine forests, СЧЗСbilberry-green moss-sphagnum pine forests), the Y-axis shows the percentage Three types of forests are subdivided within the group of long-stem moss-sphagnum pine forests: cloudberry-sphagnum pine forests, bilberry-green moss-sphagnum pine forests, and bilberry-sphagnum pine forests. The predominant type is bilberry-sphagnum pine forests, which are found only in the middle taiga (Fig. 23). Bilberry-green moss-sphagnum pine forests are found both in the northern and in the middle taiga. They represent the initial stages of waterlogging of dwarf shrub-green moss forests.

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Long-stem moss-sphagnum pine forests grow on poorly drained areas of the plains, on the smooth slopes of ridges with peaty and peaty-gley soils. Table 21). The tree layer is formed by predominant Pinus sylvestris, with Betula pubescens, Picea abies etc. can occur as an admixture (Fig. 24)   Two types of forest are subdivided within the group of dwarf shrub-sphagnum pine forests:

Dwarf shrub-sphagnum pine forests (geobotanical descriptionsee
dwarf shrub-sphagnum pine forests and ledum-sphagnum pine forests. The predominant type is dwarf shrub-sphagnum pine forests, which are found both in the northern and the middle taiga (Fig.   25). Ledum-sphagnum pine forests were found only in the middle taiga.
Dwarf shrub-sphagnum pine forests are usually located in poorly drained relief depressions or on the margins of oligotrophic bogs.  . The ratio of forest types in the group of dwarf shrub-sphagnum pine forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The X-axis shows types of forests (1dwarf shrub-sphagnum pine forests, 2ledum-sphagnum pine forests), the Y-axis shows the percentage Eumesotrophic grass-sphagnum spruce forests (geobotanical descriptionsee Table 22) are represented by only one PLP (grass-cowberry-sphagnum spruce forest), which is located in the northern taiga. The trees layer is formed by predominant Picea abies with an admixture of Betula pubescens. The shrubs layer and the understorey have a low abundance of Betula pubescens, Juniperus communis, Sorbus aucuparia, Rosa acicularis, etc. The grass-shrub layer is characterized by the presence of boreal dwarf shrubs (Vaccinium vitis-idaea), eutrophic and mesotrophic grasses.

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In the moss-lichen cover species of the genus Sphagnum are constant. Green boreal mosses (Hylocomium splendens, Pleurozium schreberi) also occur, but with low abundance.   Table 22) are represented by only one PLP (horsetail-sphagnum birch forest), which is located in the middle taiga.

Long-stem moss-sphagnum birch forests (geobotanical descriptionsee
The tree layer is formed by Betula pendula, B. pubescens, and Populus tremula. The shrubs layer and the understorey consist of a young generation of trees (Picea abies) and adult shrubs (Sorbus aucuparia). The grass-dwarf shrub layer is dominated by Equisetum sylvaticum. Vaccinium myrtillus, Gymnocarpium dryopteris, Oxalis acetosella, etc. are found as admixtures. Sphagnum mosses dominate in the moss-lichen layer: Sphagnum girgensohnii.
Floristic diversity of forests of the sphagnous section was estimated using alpha and beta diversity indicators.
Evaluation of alpha diversity. Species density in different forest types groups of the sphagnous section is virtually the same: from 28 to 29 species (Fig. 26). On the majority of PLPs about 30 plant species were identified (Tables 23-26). Long stem moss-and dwarf shrub-sphagnum pine forests show the lowest values of floristic diversity, whereas long stem moss-sphagnum spruce forests are the most diverse.

Evaluation of beta diversity. Beta diversity (Tables 27 and 28) within the sphagnous section
is estimated using Jaccard index and Whittaker's index.
In the pair-wise comparison of forest type groups of the sphagnous section, the value of Jaccard index of similarity varies from 0.3 to 0.6. Most similar in floristic composition were longstem moss-sphagnum pine and spruce forests (0.6), as well as long-stem moss-sphagnum spruce and birch forests (0.5); least similar were long-stem moss-sphagnum birch forests and eumesotrophic grass-sphagnum spruce forests (0.2). Whittaker's index value (5.7) for the sphagnous section is higher than for the forest types groups within the section (2.6-4.0).      Table 23.    (Morozova et al., 2008). There are primary (multiple-aged) and derivative spruce forests. The latter arose due to the preservation of the understorey and thinners after fellings of the middle of the 20th century (Martynenko, 1999). Long-stem moss birch forests grow in clear cur areas and burnt areas instead of green moss spruce and pine forests or instead of long-stem moss spruce forests. It is proven by the similarity of their species composition.  ----1 Comment. БДСlong-stem moss-sphagnum birch forests, СКСdwarf shrub-sphagnum pine forests, СДСlong-stem moss-sphagnum pine forests, ЕДСlong-stem moss-sphagnum spruce forests, ЕТСeumesotrophic grass-sphagnum spruce forests 4.0 2.9 2.6 --5.7 Comment. БДСlong-stem moss-sphagnum birch forests, СКСdwarf shrub-sphagnum pine forests, СДСlong-stem moss-sphagnum pine forests, ЕДСlong-stem moss-sphagnum spruce forests, ЕТСeumesotrophic grass-sphagnum spruce forests There are 15% of the northern taiga forests, and 85%of the middle taiga forests among them, mainly various birch forests. The forests of the grass section are located on poorly or moderately moist habitats, and the grass-marshon excessively moist habitats (water can stay on the surface for a long time). At the same time, both sections are characterized by poorly developed moss and lichen covers (coverage is less than 20%, although in some places it can reach 50%).
The grass and grass-marsh sections include the forests belonging to four forest type groups: small grass birch/aspen forests, grassmarsh birch forests, tall grass birch forests and tall grass spruce forests (Fig. 28). The predominant group is small grass birch/aspen forests (about 60%). The share of other groups of forest types is insignificant. Let us look at the groups of forest types of the grass and grass-marsh sections. Table 29)  Figure 28. Ratio of PLPs by groups of forest types. Grass and grassmarsh sections. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The X-axis shows groups of forest types (1small grass birch/aspen forests, 2tall grass spruce forests, 3tall grass birch forests, 4grassmarsh birch forests), the Y-axis shows the percentage  bilberry aspen forests), which are in the majority found in the middle taiga. Forb-bilberry birch forests are predominant (Fig. 30).

Figure 30.
The ratio of forest types in the group of small grass birch/aspen forests. The shaded columns stand for the northern taiga, the unshaded columnsfor the middle taiga. The X-axis shows forest types (1forb-bilberry birch forests, 2bunchgrass-bilberry birch forests, 3horsetail birch forests, 4forb-bilberry aspen forests), the Y-axis shows the percentage This group of forest types unites birch forests that appeared on the site of small grass-green moss spruce forests of the middle taiga after logging and fires. These communities grow on drained habitats, and are found on the slopes of moraine hills, on flat sections of dividing ridges and slopes of river terraces on both noncalcareous and carbonate-rich moraine loams.  Tall grass spruce forests (geobotanical descriptionsee Table 30). The tree layer is formed by the predominant Picea abies with an admixture of Betula pubescens and Populus tremula. Alnus incana, Sorbus aucuparia, Picea abies etc. were found in the layer of shrubs and understorey of trees. The restocking of Picea abies is most common there. The grass-dwarf shrub layer is codominated by Aconitum septentrionale, Vaccinium myrtillus, Equisetum sylvaticum, Oxalis acetosella as well as tall ferns. Some nemoral species are present with low abundance. The mosslichen layer has low coverage.
Within the group of tall grass and small grass spruce forests one forest type was identifiedaconite-tall fern spruce forest.
Tall grass birch forests and grassmarsh birch forests in the studied forests are found within one PLP each (geobotanical descriptionsee Table 31). These forests are represented by communities with the tree layer dominated by Betula pubescens with a small admixture of Picea abies (Fig. 31). The shrubs layer and the understorey are formed by Picea abies, Sorbus aucuparia, etc. The total share of grasses in the grass-dwarf shrub layer exceeds boreal shrubs in terms of coverage. The moss and lichen layer is almost undeveloped. and smooth slopes. Since the understorey of Picea abies is almost always seen in birch forests, such forests can gradually be replaced by spruce forests with an admixture of birch.  stand for the total number of species in the forest type group (species richness); the unshaded columnsfor the average number of species per PLP (species density). The X-axis shows groups of forest types (1small grass birch/aspen forests, 2tall grass spruce forests, 3tall grass birch forests 4grassmarsh birch forests), the Y-axisthe number of plant species (vascular plants, mosses, lichens) The floristic diversity of forests of the grass and grass-marsh sections was estimated using alpha and beta diversity indicators. Evaluation of alpha diversity. Species density in different groups of forest types of the grass and grass-marsh sections varies: from 47 to 66 species (Fig. 32). At the same time, the majority of PLPs had 40 to 60 plant species (Tables 32-34). Tall-grass spruce forests and small-grass birch forests have the highest values of floristic diversity. The tall-grass spruce forests have lower species richness as compared to small-grass birch forests due to the sample size: birch forests were found on eight PLPs, whereas spruce forestsonly on two.
Evaluation of beta diversity. Beta diversity (Tables 35 and 36) within the grass and grassmarsh sections is assessed using the value of Jaccard index and Whittaker's index.
Pair-wise comparison of groups of forest types of the grass and grass-marsh sections shows that Jaccard index of similarity varies from 0.2 to 0.6. Tall grass birch and spruce forests demonstrated the highest similarity in floristic composition (0.6); while the lowest similarity was demonstrated by grassmarsh birch forests and small grass birch forests (0.2). The value of Whittaker's index (4.3) for the grass and grass-marsh sections is higher than for groups of the forest types within the section (1.5-3.4).    3.4 1.5 --4.3 Comment. Б/ОМ -small grass birch/aspen forests, ББТgrassmarsh birch forests, БВtall grass birch forests, EBtall grass spruce forests Ecological-coenotic structure of forests. The results of the floristic list-based calculation of the ecological-coenotic structure of species diversity have shown that forests of the grass and grass-marsh sections have a fairly diverse set of ecological-coenotic plant groups (Fig. 33). These forests are dominated by boreal forest species of all life forms: trees, shrubs, dwarf shrubs and grasses. The share of nemoral and wetland types is high. Nitrophilous plants were found. The share of meadow and forest-edge plants is insignificant, which is typical for the taiga forests.