BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

XIV. TOOLS AND METHODS FOR THE STUDY OF AQUATIC VEGETATION

Determination of the coenotic composition of aquatic vegetation.

The coenotic composition is studied in the course of plant community Classification (syntaxonomy), which, unlike classification at the Organism level (Taxonomy), reflects not The history of the plant world's development, but rather the "ecological and successional Differentiation of the plant continuum" [62]. Numerous classifications have been developed, but most of them are based on two main approaches: the ecologo-physiognomic and the ecologo-floristic (the Braun-Blanquet approach).

The ecologo-physiognomic classification involves the delineation of syntaxa based on projective cover values and the biomorphological features of dominant species (or a species). Hierarchically, the classification is structured as follows: vegetation type – formation Class – formation group – formation – association. The fundamental units of classification are the association and the formation. V. M. Sukachev [85] suggested distinguishing ecological variants of associations, whereas A. P. Shennikov [99] proposed utilizing climatic, regional, successional, and edaphic features to identify various subassociations. In hydrobotany, such a subdivision was not widely adopted; instead, the association is considered the smallest taxonomic unit, uniting phytocoenoses that are homogeneous in their floristic composition, Structure, synusiae, and The Nature of interrelationships among themselves and with the environment.

When delineating associations, primary attention is paid to 2–3 dominant species (of the same or different tiers). A formation is a set of associations sharing a common dominant in the uppermost tier. Formation names are formed by adding the suffix "eta" to the ROOT of the Latin generic name (Potamogetoneta perfoliate, Nymphaeeta candidae). Associations are usually named according to a binomial nomenclature: the first word consists of the generic name of the dominant from the upper tier with the suffix "etum" added to its root, and the second consists of the generic name of the subordinate tier's dominant with the suffix "osum" added – for example, Nupharetum ceratophyllosum (demersi), Typhetum (angustifoliae) potametosum (perfoliatae). If two dominants prevail in the uppermost tier, both are used in the name (Typheto-Phragmitetum), and the same applies to the second part of the association name. In the case of a single-species association, the word "purum" is added to its name (Phragmitetum australis (purum)).

Since several species frequently dominate in aquatic coenoses, a simpler approach is to list their Latin names. Here, the sign "-" separates species of different ecological groups (tiers), while "+" separates species of the same tier. The list of species begins with emergent plants and ends with submerged ones (Phragmites australis + Typha angustifolia - Nuphar lutea - Potamogeton pectinatus). The projective cover of the species is also indicated. In Ukrainian names of associations, the subdominant is placed first and the dominant second; for example, the reed-cattail association denotes a cattail community with an admixture of reeds. Such a classification is extremely simple and convenient for preliminary data Processing. Syntaxa are established directly during fieldwork.

Currently, the majority of phytocenologists worldwide prefer ecologo-floristic classifications based on the similarity of the floristic composition of plant communities. This feature characterizes the response of species to environmental conditions and to each other better than others [129]. The primary, though not the smallest, taxonomic unit is also the association – a grouping of plant communities with a common combination of diagnostic units. Based on a block of diagnostic species, and taking into account additional criteria of habitat and appearance, associations are grouped into higher-ranking syntaxa: alliances, orders, and classes. For instance, physiognomic features take precedence in defining a class, with floristic composition coming second (the class LEMNETEA R. Tx. 1955 unites communities of free-floating unrooted plants on the Water surface and in the water Column; the class PHRAGMITI-MAGNOCARPICETEA Klika in Klika et Novak 1941 unites communities of bogs, swampy meadows, and coastal shallows). An order is a variant of a class, distinguished on The basis of floristic, physiognomic, and ecological criteria; within the class LEMNETEA, three orders are distinguished – Lemnetalia R. Tx. 1955, which unites communities of small pleustophytes of shallow waters with limited water exchange; Hydrocharitetalia (Rübel, 1933), uniting larger species freely floating On the surface and in the water column of predominantly swampy, eutrophic, weakly flowing water bodies; and Lemno-Utricularietalia (Passarge, 1978), representing coenoses of species floating in the water column and on The surface of swampy, closed eutrophic, and hyper-eutrophic water bodies with limited water exchange [60]. Taking into account edaphic, geographical, climatic conditions, and the successional stage of the association's development, it can be subdivided into smaller units: subassociations, variants, and facies.

Syntaxa are identified through complex processing of phytocenological tables and thus cannot be determined under field conditions. The Procedure for selecting sites for geobotanical descriptions, compiling and processing tables, establishing taxa of various ranks, and naming them is described in detail in the works of V. D. Aleksandrova [1], V. N. Sukachev [85], Tüxen [129], D. V. Dubyna, J. Hejný, Z. Grulich, et al. [57].

Although the association serves as the "foundation" of syntaxonomy, there are no clear criteria to state unambiguously that a given set of descriptions (phytocoenon) is specifically an association rather than a subassociation or an alliance. This can only be established by comparing the obtained data with already known ones. Any syntaxon acquires its name and is strictly documented using published phytocenological tables that initially contain at least 10 geobotanical descriptions with a complete list of species and their degree of Participation in the community. The name is also accompanied by the author's name and year of publication. In foreign literature, typing of existing syntaxa is ongoing, and new syntaxonomic solutions constantly emerge. In our country, a prodrome for vascular aquatic and wetland vegetation has been developed. The situation regarding communities of aquatic mosses and macroscopic Algae is considerably less advanced.

The Braun-Blanquet system is in a state of continuous development. Several classification variants may be applied in parallel for any given region. Each new publication of regional taxon lists can lead to a revision and updating of the classification: new units are simply integrated into the system, or the entire system begins to "shift" as the ranks of syntaxa change. The main rule in this process is to strictly follow the "Code of Phytosociological Nomenclature" (1988) and not to rename previously distinguished units while preserving their scope.

In the classification of aquatic and coastal communities with a depleted floristic composition, the dominance criterion is paramount. However, this is insufficient on its own, so A number of additional features are also utilized – habitat conditions, geographical position, dynamic status of the association, and Morphology/18.html">PLANT LIFE FORMS.