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

I. CONDITIONS FOR THE FORMATION AND GROWTH OF AQUATIC PLANTS

Siltation and Overgrowth of Water Bodies

Siltation and overgrowth are part of the accumulative process involving the continuous deposition of silt and the changing depth of a Water body. Siltation alters water depth and occurs As a result of the interaction between mineral-organic matter and the remains of aquatic macrophytes brought in by currents, which accelerates the process. In delta lakes, this role is played predominantly by the common reed (Phragmites australis). In lakes, oxbows, isolated channels, and ponds, accumulation is driven by species with high annual productivity and continuous autochthonous sedimentation of plant residues. These include rigid hornwort (Ceratophyllum demersum), spiked water-milfoil (Myriophyllum spicatum), and Canadian waterweed (Elodea canadensis).

The filling of a water body occurs primarily through plant debris (stem fragments, roots, rhizomes) that remain on the water surface as floating mats or small islands. A subsequent condition for The formation of such masses is the germination of seeds of helomorphic species, which produce juvenile individuals and develop into new plant clones, forming an accumulation of debris—an island—as a foundation for further plant colonization.

In the temperate zone of the Northern Hemisphere, in tundra and taiga water bodies, the main material for the formation of quaking bogs (schwingrasen) consists of floating substrates that detach from the main peat mass located at the bottom. The presence of living plants (primarily sphagnum mosses) is mandatory. In middle latitudes, and especially in southern regions, the primary material consists of reed beds and tussocks of large sedges.

There are A number of differences between an island (accumulation) and a mat. An island is a detached, solid substrate that reaches a depth of 30–60 cm or consists of roots and rhizomes forming the Skeletal Structure of reed stands, overgrowing with species of the alliance Cicution virosae or large sedge species.

A mat is a continuous substrate reaching a depth of 10–20 cm, homogeneous in terms of substrate and heterogeneous in terms of constituent vegetation. It forms a continuous "blanket" incapable of supporting objects weighing more than 50 kg. It originates both autochthonously and allochthonously.

When a mat connects with an island, a primary synecotline of unanchored soils emerges, functioning as an ecologically distinct habitat with phytocoenosis species of the alliance Cicution virosae. From a biocenological perspective, these communities are stenotypic because The ROOT System is located in both the bottom and floating substrates. Diagnostic species include Cicution virosae and Oenanthion aquatica (narrow ecological amplitude) alongside species of the orders Phragmitetalia and Magnocaricetalia (wide amplitude). Because some macrophytes have The ability to sprout on such substrates, the island and the mat thereby become connected.

Based on the germination of species seeds on unanchored substrates, 4 types are distinguished:

fern type — an entanglement of roots, rhizomes, and masses of decomposing above-ground shoots (paniculate sedge (Carex paniculata), lesser tussock sedge (C. diandra), slender tussock sedge (C. acuta), reed sweet-grass (Glyceria aquatica), etc.);

Cellulosic type — germination driven by the anchoring of seeds and diaspores within the intercellular spaces of stems and in wood crevices (narrowleaf cattail (Typha angustifolia), broadleaf cattail (T. latifolia), branched bur-reed (Sparganium erectum));

Combined type — a combination of the fern type and the cellulosic type (Phragmites australis);

Skeletal type — germination is driven by seeds and diaspores falling into sapropel On the surface of the Skeleton, or by the accumulation of rhizomes (Scirpus lacustris).

The base of small islets is formed by many species, most frequently including slender tufted sedge (Carex pseudocyperus), water hemlock (Cicuta virosa), water dock (Rumex hydrolapathum), skullcap (Scutellaria galericulata), as well as Representatives of the genera beggarticks (Bidens) and willowherbs (Epilobium).

The appearance of islets is typical of habitats where plant communities of the alliance Cicution develop for the sapropelic type. Under such conditions, they can originate both autochthonously and allochthonously on a dead substrate formed by species of the Caricetum paniculatae formation. Islets are formed mainly in channels by the anchoring of small fragments torn off from reed quagmires along the shores of lakes and bays (through the movement of small fragments from reed beds). The anchoring base for an islet is provided either by a skeleton of reed rhizomes or by a colony of phytocoenosis species belonging to the alliance Spargonio-Glycerion. The Emergence of islets is characteristic of the migratory type of development.

In the sapropelic type of unconsolidated soils, floating mats are formed when species spread via plagiotropic rhizomes, creating a substrate for the establishment of other species (such as bog arum, Calla palustris) and facilitating subsequent colonization by other taxa. In the migratory type, mat formation occurs when the quagmire possesses a relatively homogeneous skeleton consisting primarily of stems rather than rhizomes, or when the supporting skeleton is submerged in shallow water.

In ditches, floating mats are formed when species with plagiotropic rhizomes predominate, their growth directed by the current (bog arum (Calla palustris) + bittersweet nightshade (Solanum dulcamara) + water mint (Mentha aquatica)). They are also characteristic of the insular type of quagmire formation following the dieback of reed fragments. This process is more typical of ponds than of lakes.

In ditches, mats usually form directly through the overgrowth of the surface water layer and constitute a core element of the vegetation cover. The processes of anchoring, overgrowth, and the formation of quagmire vegetation have been the subject of numerous studies [21, 29, 82, 86], conducted primarily in the deltas of southern rivers. The initial stage of quagmire formation in the water bodies of the Northern Black Sea river deltas is the establishment of rhizome networks by common reed (Phragmites australis), narrowleaf cattail (Typha angustifolia), and other aquatic macrophytes such as water pepper (Polygonum hydropiper), water mint (Mentha aquatica), European bugleweed (Lycopus europaeus), marsh hedgenettle (Stachys palustris), and water hemlock (Oenanthe aquatica), among others. According to D.V. Dubyna and Yu.R. Shelyag-Sosonko (1989), 96 species of flowering plants have been identified in the wetlands of the Kilia Danube Delta, 86 in the Dniester Delta, 81 in the Dnieper Delta, 51 in the Kuban Delta, 54 in the Don Delta, and 24 in the Southern Bug Delta. The final stage of quagmire formation is their stabilization. Subsequently, plant communities begin to develop on these substrates, running parallel to the processes of reservoir siltation and overgrowth.

The overgrowth of floodplain eutrophic water bodies occurs more intensively and over larger areas. Among emergent and floating-leaved macrophytes, the main contributors to overgrowth in the water bodies of the Ukrainian Polissya are reed sweet-grass (Glyceria maxima) and lake bulrush (Scirpus lacustris), while true aquatic species include dark-green hornwort (Ceratophyllum demersum), clasping-leaf pondweed (Potamogeton perfoliatus), shining pondweed (Potamogeton lucens), and spiked water-milfoil (Myriophyllum verticillatum). In the Forest-Steppe zone, these same species are joined by common reed (Phragmites australis), narrowleaf cattail (Typha angustifolia), broadleaf cattail (Typha latifolia), branched bur-reed (Sparganium emersum), fennel pondweed (Potamogeton pectinatus), Eurasian water-milfoil (Myriophyllum spicatum), and thread-leaf water-crowfoot (Batrachium foeniculaceum), among others. In the Steppe zone, emergent species dominating the overgrowth include common reed (Phragmites australis), narrowleaf cattail (Typha angustifolia), Tabernaemontana bulrush (Scirpus tabernaemontani), and reed mannagrass (Glyceria arundinacea), alongside true aquatics such as fennel pondweed (Potamogeton pectinatus), Rion's water-crowfoot (Batrachium rionii), horned pondweed (Zannichellia palustris), and flat-spined hornwort (Ceratophyllum platyacanthum). The most typical generalized ecological zonation for water bodies in the northwestern Ukrainian Polissya (from the shore toward the center of the water body) can be represented by the following sequence: Omsk sedge (Carex omskiana) — sharp sedge (Carex acuta) — reed sweet-grass (Glyceria maxima) — unbranched bur-reed (Sparganium erectum) — dark-green hornwort (Ceratophyllum demersum) — clasping-leaf pondweed (Potamogeton perfoliatus) — yellow water-lily (Nuphar lutea). In the southern regions and the Left-Bank part of the Ukrainian Polissya, the following ecological series are more characteristic: sharp sedge (Carex acuta) — reed sweet-grass (Glyceria maxima) — common reed (Phragmites australis) — dark-green hornwort (Ceratophyllum demersum); shining pondweed (Potamogeton lucens) — clasping-leaf pondweed (Potamogeton perfoliatus) — yellow water-lily (Nuphar lutea).

The most typical generalized ecological overgrowth series for floodplain water bodies of the Left-Bank Forest-Steppe is as follows: sharp sedge (Carex acuta) — reed sweet-grass (Glyceria maxima) — branched bur-reed (Sparganium emersum) — Canadian waterweed (Elodea canadensis) — dark-green hornwort (Ceratophyllum demersum) — shining pondweed (Potamogeton lucens). For the Right-Bank Forest-Steppe: sharp sedge (Carex acuta) — water dropwort (Oenanthe aquatica) — arrowhead (Sagittaria sagittifolia) — Canadian waterweed (Elodea canadensis) — floating pondweed (Potamogeton natans) — yellow water-lily (Nuphar lutea). In the southern Regions of the Forest-Steppe, the following ecological series is characteristic: common reed (Phragmites australis) (broadleaf cattail (Typha latifolia)) — flowering rush (Butomus umbellatus) (arrowhead (Sagittaria sagittifolia)) — dark-green hornwort (Ceratophyllum demersum) — fennel pondweed (Potamogeton pectinatus) — Eurasian water-milfoil (Myriophyllum spicatum).

The most typical and generalized ecological overgrowth series for floodplain water bodies of the Steppe zone is represented by the following scheme: common reed (Phragmites australis) — narrowleaf cattail (Typha angustifolia) — dark-green hornwort (Ceratophyllum demersum) — Eurasian water-milfoil (Myriophyllum spicatum) — fennel pondweed (Potamogeton pectinatus).

The overgrowth of shallow waters in large reservoirs begins with monospecific communities of creeping bentgrass (Agrostis stolonifera), reed sweet-grass (Glyceria maxima), unbranched bur-reed (Sparganium erectum), narrowleaf cattail (Typha angustifolia), water-smartweed (Polygonum amphibium), and floating pondweed (Potamogeton natans) (Ukrainian Polissya); reed sweet-grass (Glyceria maxima), narrowleaf cattail (Typha angustifolia), flowering rush (Butomus umbellatus), arrowhead (Sagittaria sagittifolia), and clasping-leaf pondweed (Potamogeton perfoliatus) (Forest-Steppe); common reed (Phragmites australis), Eurasian water-milfoil (Myriophyllum spicatum), and fennel pondweed (Potamogeton pectinatus) (Steppe). Within 4–5 years, almost all shallow areas become overgrown with emergent and aquatic plant communities.

Generalized overgrowth series for large reservoirs are represented by the following schemes: common reed (Phragmites australis) — narrowleaf cattail (Typha angustifolia) — dark-green hornwort (Ceratophyllum demersum) — yellow water-lily (Nuphar lutea) (Ukrainian Polissya); common reed (Phragmites australis) — narrowleaf cattail (Typha angustifolia) — clasping-leaf pondweed (Potamogeton perfoliatus)

white water-lily (Nymphaea alba) (Forest-Steppe); common reed (Phragmites australis) — Ceratophyllum platyacanthum — Eurasian water-milfoil (Myriophyllum spicatum) — fennel pondweed (Potamogeton pectinatus) — white water-lily (Nymphaea alba) (Steppe).

The overgrowth of artificial water bodies with altered shorelines (modified for fishery needs) exhibits distinctive features. In water bodies with muddy-sandy bottom sediments (Polissia), the overgrowth is dominated by reed sweet-grass (Glyceria maxima), lesser bulrush (Typha angustifolia), and dark-green hornwort (Ceratophyllum demersum); in those with sandy-muddy sediments (Forest-Steppe), common reed (Phragmites australis), amphibious bistort (Polygonum amphibium), and Berchtold's pondweed (Potamogeton berchtoldii); and in muddy sediments (Steppe), sago pondweed (Potamogeton pectinatus), yellow floating-Heart (Nymphoides peltata), and spiked water-milfoil (Myriophyllum spicatum).

The overgrowth of shallow estuaries has its own specific characteristics, notably the degree of water mineralization and its connection to the sea. In brackish estuaries isolated from the sea, the ecological succession in the shallows of the middle section can be represented as follows: sago pondweed (Potamogeton pectinatus) - horned pondweed (Zannichellia palustris) - coastal widgeon-grass (Ruppia cirrhoza) - dwarf eelgrass (Zostera noltii) - eelgrass (Zostera marina); common reed (Phragmites australis) - sea club-rush (Bolboschoenus maritimus) - soft-stem bulrush (Scirpus tabernaemontani) - dark-green hornwort (Ceratophyllum demersum) - sago pondweed (Potamogeton pectinatus) - horned pondweed (Zannichellia palustris); common reed (Phragmites australis) - sea club-rush (Bolboschoenus maritimus) - dark-green hornwort (Ceratophyllum demersum) - clasping-leaf pondweed (Potamogeton perfoliatus); in areas of the maritime section: common reed (Phragmites australis) - sea club-rush (Bolboschoenus maritimus) - dark-green hornwort (Ceratophyllum demersum) - coastal widgeon-grass (Ruppia cirrhoza) - horned pondweed (Zannichelliapalustris).

Thus, the leading drivers of aquatic vegetation successions are hydrological, geological (alluvial), and anthropogenic factors. The most pronounced successions are those driven by fluctuations in water level, water mineralization (in southern regions), water body trophicity, and the composition and thickness of bottom sediments.