Tendencies of structure profile FOREST communities change in Recreational zone
Piskunov V.V., Davidenko T.N. (Saratov State University, Russia)
Рассмотрены основные направления изменения профильных характеристик и структурных компонентов лесных растительных сообществ в рекреационных зонах юга Приволжской возвышенности.
In forests of the Saratov Right bank from the moment of mass fading an oak trees processes of transformation of oak groves in other wood communities have begun. On sandy and loamy soils the lime-tree (Tilia cordata L.) began to occupy conducting positions. In other conditions the mixed forest stands began to be formed of an oak (Quercus robur L.), a lime-tree, a birch and aspens (Populus tremula L.).The maple (Acer platanoides L.), earlier not being dominant species, began to take root actively into these communities (Boldyrev, 2005). The phenomena of transformation in the most expressed kind are marked in forest stands of a recreational zone where there is a reduction of a share of participation of an oak and a lime-tree in structure of a wood and increase in the area of forest stands to a significant impurity of a maple. Now the most part of the area of suburban woods are represent transitive communities - borrow maple-oak groves, oak-maple, maple-lime-tree and lime-tree-maple. Invading of Acer platanoides results in formation of communities which structural components considerably differ from earlier existing and are characterized by some features.
During our research character of structure change of separate strata and all phytocoenosis profile in such forest community as lime-tree → maple-lime-tree → lime-tree-maple was studied and prominent features of their structural organization was revealed. In each type of communities it is incorporated on 15 sample plots in the size 400 m2, on which the description of structural characteristics with use standard phytocoenosesis (Korchagin, 1976) and the specialized techniques is lead (Blondel, Сurvillier, 1977; Erdelen, 1988).
By the greatest structural diversity are characterized lime-tree phytocoenosis. Significant vertical and horizontal heterogeneity, a variety of a projective covering of foliage at various high-altitude levels, a high projective covering of a underbrush and a herbage is marked in community of this group. In the majority of communities in structure of a stand as an insignificant impurity meet Acer platanoides, Populus tremula, less often - Ulmus laevis Pall. The average height of a forest stand makes 16,5 m. A density of crones - 70%. Acer platanoides is dominates in regrowth, less often - a lime, sometimes meet an elms (Ulmus laevis Pall., Ulmus glabra L.). The underbrush is more often rarefied, is submitted by Corylus avellana L. and less often - Euonymus verrucosa L. The general projective covering of a grassy reaches 85%, a herbage are rich, but low.
The most widespread variants lime-trees forests - Tilia cordata–Convallaria majalis and Tilia cordata–Aegopodium podagraria - borrowing bottom parts of slopes of northern exposition and the bottom of beams; they are characterized by the most complex strata organization and a variety of a projective covering of foliage at various high-altitude levels (Fig.).
Total density of foliage of the bottom profile reaches values of 85%. The greatest contribution to formation of such high values brings presence of a underbrush and regrowth which height does not exceed 1,5 м, forming practically uniform covering on a plot. As a whole for the given communities significant differences of a projective covering of foliage in various high-altitude intervals are characteristic. It defines significant heterogeneity of a vertical phytocoenosis structure and high values of an index of a total projective covering of foliage - 0,69.
Structure profiles lime-trees forests, slopes of northern exposition occupying average part differ from the previous communities smaller heterogeneity and lower values of a density of the bottom of the profile. For average and top parts of a profile (height 5-15 m) the big uniformity and higher total quantitative values of a projective covering of foliage is marked. Prominent feature of shrub is low density and monodominants. Prevailing Euonymus verrucosa, as a rule, does not reach height more 1,5 m, that determines presence in a high-altitude interval 1,5-2,0 m the lowest value of a projective covering of foliage. Total value of an index of a projective covering of foliage here is a little bit lower - 0,64.
Maple-lime-tree forests characterized by other structural organization. For all variety of these phytocoenosis typically same profile structure. The general density of foliage on all high-altitude intervals in 1,2-1,3 times is less, than in lime-tree forests. The low projective covering of the bottom stratum, and insignificant density of crones regrowth is marked. The maximal projective covering of foliage (up to 90%) is typical of heights 7-9 m (see Fig.). It is connected to smaller height of Acer platanoides in comparison with Tilia cordata and with features arhitecnonics its crones. Regrowth is submitted basically by a maple, which average height - 4,5 m. The least projective covering of foliage is registered at height 2,5-5,5 m. Distinctive feature of a structure maple-lime-tree forests is practically identical values of a density of foliage at heights 0-2м. It is connected to presence in regular distributed underbrush which is combined mainly by Acer tataricum L. and Euonymus verrucosa. A projective covering of a underbrush - 40-50%. A herbage more rarefied; despite of a high specific variety of a grassy, much less its total projective covering (on the average 53%).
The structure of lime-tree-maple forests is differ from the previous communities a little bit short vertical structure and characterized by significant change of a share of participation of components in addition of a total projective covering of foliage of the bottom circles. A density of crones is 45-60%. The monotony of a projective covering is typical of the low stratum of community. The basic contribution to formation of a high projective covering of foliage of the bottom profile - up to 70% - brings a maple which average height makes 3,5 m. Prominent feature - is high regrowth saturation (up to 15 экз/m2). The underbrush is combined by Euonymus verrucosa, is strongly rarefied and rather uniform on height (0,6-1,1 m). Its projective coverings is low - 20-30%. The herbage is very diversity by species, but not density. Prominent feature is practically full absence mosaic structure. The average projective covering of it makes 30%. The average height of a grassy makes 0,32 m. In comparison with maple-lime-tree forests, the structure of the given communities is characterized by the big total projective covering of foliage (0,58 against 0,52) and substantial growth of density of foliage in an interval 2,5-5,5 m.
Thus, by results of our research it was revealed, that during modern dynamics of wood vegetative communities changes of different structural components and a vertical structure phytocoenosis as a whole are observed. In a number lime-tree → maple-lime-tree → lime-tree-maple there is a reduction of height of a wood, reduction of a variety of a covering of foliage in various high-altitude intervals, decrease of a total density of foliage, increase regrowth density, decrease of a projective covering and heights of a herbage.
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