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

XIV. INSTRUMENTS AND METHODS FOR THE STUDY OF AQUATIC VEGETATION

Description and Mapping of Aquatic Vegetation

Before starting this work, it is necessary to review the literature and other Materials regarding the studied object. This will significantly expedite The Study of Water bodies. During preliminary reconnaissance route surveys, a general characterization of the water body's vegetation is conducted: the dominant flora in the plant cover formation and its distribution features. Detailed route-based field studies provide a comprehensive characterization of the water body's vegetation, including the identification and Classification of vegetation units, their composition, Structure, ecology, distribution, and area.

Studying aquatic vegetation is labor-intensive and requires specialized transport and tools. Simply observing the vegetation from the shoreline is insufficient. A rowboat is needed, along with a 2-3 m long pole with a fork at the end, which serves as an anchor while describing sample plots. It is best to work in pairs. For small water bodies, ponds, and pools, a rubber dinghy can also be used. A reconnaissance tour is conducted prior to the description. During this tour, stops are made to describe plant communities. The field diary records the patterns of vegetation distribution along the shoreline, its composition, physiognomy (appearance) and vitality, ecological conditions, and visual sketches of community distribution in specific areas of the water body. Ecological profiles and linear transects are established in various PARTS OF THE water body to describe and record the vegetation, and to determine the dimensions of phytocenoses and littoral vegetation belts. These materials are used to compile a schematic map of vegetation distribution within the water body. The number of descriptions depends on the degree of overgrown state, size, and purpose of the study.

Mapping. The specifics of aquatic vegetation mapping are described by A.P. Belavskaya [6]. When compiling schematic maps, one should not be limited to outlining visible vegetation boundaries; it is equally necessary to map the boundaries of submerged and bottom communities. Specialized tools are used for this purpose. The mapping of aquatic vegetation distribution is carried out visually from a boat, or by measuring distances between different vegetation types using poles, measuring cords, and near the shores - with a tape measure or measuring line. Conventional symbols are used to designate various vegetation units (associations, formations) when drafting vegetation distribution maps in water bodies. Each researcher uses their own unique symbols and hatching patterns. Emergent plants are designated with vertical lines, floating-leaved plants with circles, and submerged plants with triangles (pondweeds), squares, rectangles, etc. To indicate vegetation thickets through hatching: diagonal hatching to the right is proposed for emergent plant formations, wavy horizontal hatching for floating-leaved formations, and vertical hatching for submerged formations. Hatching is applied sparingly to designate plant community letters. The area of the water body's vegetation is calculated using the maps.

To determine the overgrowth status of ponds, the following indicators are used:

+ 5 - excessive overgrowth, vegetation covers more than 50% of the pond surface;

5 - extremely high - 36-50%;

4 - high - 21-35%;

3 - moderate - 11-20%;

2 - low - 3-10%;

1 - sparse - 1-2%.

Study of Aquatic Vegetation and Phytocenosis Structure. Below are some terms and concepts used in the study of aquatic vegetation. Geobotanists have interpreted METABOLISM/2.html">THE CONCEPT OF phytocenosis in various ways. In particular, the renowned Russian scientist V.N. Sukachev [84] characterized phytocenosis as follows: "A phytocenosis (plant community) should be understood as any assemblage of plants in a given territory that are in a state of interdependence and characterized by a specific Composition and Structure, as well as a specific relationship with the environment. This interdependence is determined by the fact that plants Struggle for Existence among themselves, which sometimes determines the possibility of certain plants existing within phytocenoses." While A number of other Definitions of phytocenosis could be cited, it is clear that a phytocenosis is an assemblage of plant organisms growing in a specific territory and interacting closely both with each other and with environmental conditions. As a result, new quantitative and qualitative relationships emerge among the Components of the phytocenosis, determining its floristic composition, structure, vitality, succession, stability, and productivity, and consequently its economic significance and biological value.

A synusia is an ecologically and spatially isolated part of a plant community. From the perspective of vertical stratification, each tier of a phytocenosis is essentially a synusia, as it possesses a clearly defined spatial expression and geomorphological affinity, which in turn is determined by the ecological characteristics of its habitat. A distinction is made between main or edificator synusias, which form the largest phytomass and shape the environment of the plant community, and subordinate synusias [51].

The components of a phytocenosis, based on their Participation in the creation of phytomass and projective cover, are divided into edificators - the community builders that determine the phytocenotic environment, and esectators - companion or filler species that have little influence on environmental formation from within [84]. Dominants are species that prevail and rule in the phytocenosis and its tiers. There may be several of them. Secondary dominants and edificators are called subdominants and subedificators. Lists of edificators and dominants for aquatic plant communities are provided by Ye.M. Lavrenko [51]. The aquatic cover edificator *Phragmites australis* has been studied in extreme detail [34].

Characteristic species are considered to be those that best reflect THE ECOLOGICAL AND phytocenotic environmental conditions and significantly influence them through their Abundance, projective cover, vitality, stability, mass, etc. There is no universally established concept of vertical stratification for aquatic plants.

O.O. Korchagin [44] proposed distinguishing 3 main tiers (with height sub-tiers) for aquatic vegetation: 1. Aerial. 2. Floating. 3. Submerged. B.O. Bykov (1957) distinguished 5 tiers: 5. Floating-leaved grasses. 4. Tall grasses. 3. Medium grasses. 2. Low grasses. 1. Bottom grasses. V.M. Katanskaya [37] identifies 7 tiers: emergent - tall, medium-tall, and low emergent plants (1st, 2nd, and 3rd magnitude grasses); floating - plants with floating leaves; submerged - tall and medium-tall submerged plants, and small, low-growing bottom plants - benthic tier.

Descriptions of aquatic vegetation and studies of phytocenosis structure are carried out on sample plots [99, 106, 107, 115]. The Methods used by geobotanists in studying mire and terrestrial vegetation are described in detail. During the study of aquatic vegetation, these issues have not received adequate attention [38, 60]. The sizes of sample plots are the same as those for terrestrial grass communities. The number and size of sample plots used to determine abundance, projective cover, and other Structural elements of the phytocenosis depend on the stand structure, its density, homogeneity, and other characteristics.

Descriptions of phytocenoses are carried out on sample plots measuring 100 sq. m, usually in the shape of a square (10 x 10 m), established in the most representative locations of the selected aquatic plant community with uniform ecological conditions. Boundaries are marked visually or using poles, tape measures, and measuring lines with buoys or range poles. Phytocenotic descriptions on sample plots must be recorded on special forms (see vegetation description form). These record: the general state of the phytocenosis, its physiognomy, floristic composition, abundance, distribution pattern (evenly, in patches, in groups, singly), stratification, plant height by tiers and the height of their emergent part, projective cover - general for the entire stand and for each tier separately (and if possible for individual species), vitality, phenological state (designation of phenophases: vegetative - v., budding - b., flowering - fl., fruiting including fruit ripening - fr., presence of ripe fruits and seed production - s., dying off - d.).

When determining abundance and frequency (occurrence), records are entered into the form. The same applies to describing the habitat CHARACTERISTICS OF THE phytocenosis: depth (at the upper and lower limits), water Temperature - at the bottom and near the surface, and visual properties of bottom sediments.

Floristic composition entails a complete list of plants forming the phytocenosis. All species encountered on the sample plot are entered into the form. Plants unfamiliar to the researcher are assigned a sequential number and collected for the herbarium, while the label indicates the assigned number and description number. Plant species should preferably be identified by tiers, starting from the upper - emergent tier. Water rakes or a viewing tube should be used to detect plant species.

Abundance refers to the degree of a species' participation in the phytocenosis. For this purpose, the Drude abundance scale is best used:

Drude's scale for assessing species abundance.

Soc. (*sociales*) - 6 (abundant, forms the Background, closed canopy);

Cop. (copiosae) - 5 (extremely abundant);

Cop 2 - 4 (abundant);

Cop 1 - 3 (fairly abundant);

Sp. (sparsae) - 2 (scarce, in small quantities, scattered among other plants);

Sol. (solitariae) - 1 (solitary);

Un. (unicum) - found as a single specimen;

Gr. (gregarius) - occurring in groups (this mark is placed alongside abundance categories).

In aquatic vegetation studies, volumetric plant abundance is also used (The ratio of the sum of the volumes of spaces enclosed within the branchings of each plant of a given species to the total volume of water occupied by the plant community).

Abundance (density, population density) is determined by counting plant specimens or their shoots (in rhizomatous species) per unit area.

Such counts are carried out per 1 m² in triplicate. The counted plants are marked by snapping. In communities of floating and submerged plants at shallow depths (0.5–0.6 m), counts are performed from a boat using a frame placed on the water surface. It is difficult to count the stems of brittle submerged plants (Ceratophyllum species) or those rooted at the bottom (dense thickets of Najas marina, etc.).

Stand density of a species is determined by measuring the distance between the bases of individual specimens or different species within the sample plot (distance method). A random individual is taken as the center, and the distance to the four nearest individuals of a given species is measured. Subsequently, the same Procedure is repeated from other individuals of the studied species. It is also recommended to determine the basal area of the plants.

Projective cover is the area of horizontal projections of plants onto the soil (bottom) surface, expressed as a percentage of the sample plot area, which is taken as 100%. A distinction is made between total projective cover, tiered cover, and projective abundance—the projective cover of individual species. True cover is the area of the bottom occupied by the bases of plant stems. Projective cover is determined using devices proposed by L. G. Ramensky [71] with the aid of a grid, mirror grid, or scale fork (Fig. 222). Projective cover can also be estimated visually. This method is widely used in reconnaissance surveys.

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Fig. 222. Ramensky devices for quantitative plant recording.

1 - grid; 2 - mirror grid; 3 - scale fork;

4 - transect fork. Dimensions in cm.

Frequency (constancy) - the frequency of occurrence of a species is determined using small sample plots established within the sample area in a phytocenosis. The size of the sample plot is 0.1-1.0 m, with a quantity of 25-50 units depending on the size of the phytocenoses. Frequency is determined as a percentage representing the ratio of the number of sample plots in which the species occurs to the total number of sample plots.

Vitality - the degree of development or suppression of a species in a phytocenosis. In geobotany, the following categories of species vitality are used:

3 - the species in the phytocenosis completes its full developmental cycle and grows, develops, vegetates, flowers, fruits, and disseminates fruits and seeds normally;

3 a - the species in the phytocenosis completes its full developmental cycle, where all its phases (vegetation, budding, flowering, and fruiting) conclude and seeds are formed, but with low activity in fruit and seed dispersal; the species has a somewhat weakened vitality and is passive;

3 b - the species in the phytocenosis goes through all Selection/3.html">Stages of development, but does not reach normal size and does not shed seeds;

2 - the species in the phytocenosis has optimally expressed and developed vegetative Organs, vegetates, and even flowers, but does not complete the full developmental cycle and does not form fruits or seeds;

1 - the species only vegetates, is in a depressed state, does not flower or fruit, does not develop Generative organs, and often dies off at the seedling stage.

Pattern of distribution - indicates how a species is distributed within the study area: it can be clumped (gr.), diffuse (diff.), continuous (cont.), patchy (patch.), or solitary (sol.).

Plant volumes are determined by immersing the plants in a graduated cylinder and calculating the volume of displaced water.