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

XIII. PLANT INDICATORS OF SURFACE WATERS

Tidal zones of marine coasts

The distribution of vegetation on low-lying sea coasts corresponds to the duration of tides [44]. Along the shores of the Mezen Bay of the White Sea, in areas subject to the longest and daily inundation by Water, marsh-saltmarsh vegetation predominates: communities of seashore water-milfoil (Hippuris maritima), whitish bentgrass (Agrostis albida), maritime bentgrass (A. maritima), one-scaled spikesedge (Eleocharis uniglumis), saltmarsh alkaligrass (Puccinellia maritima), and Swedish alkaligrass (P. suecica) [43]. Terrace areas that are flooded daily, but for a shorter period and are better drained, are occupied by meadow-saltmarsh vegetation: communities of subpolar plantain (Plantago subpolaris), Baltic rush (Juncus gerardii), seaside plantain (Plantago maritima), sea arrowgrass (Triglochin maritima), nodding foxtail (Alopecurus ventricosus), subspathulate sedge (Carex subspathacea), and creeping couch grass (Elytrigia repens), the distribution of which depends on soil salinity. Elevated sections of the marine terrace, remote from the coast and not subject to daily tides, are flooded about twice a month during high spring tides and severe storms. They are occupied by meadow-bog vegetation, where, depending on soil moisture and salinity, Norwegian sedge (Carex norvegica), red fescue (Festuca rubra), giant bentgrass (Agrostis alba), northern reedgrass (Calamagrostis neglecta), and common reed (Phragmites communis) predominate. The non-inundated coastal plain is occupied by terrestrial vegetation with grass-forb communities featuring red fescue (Festuca rubra), chives (Allium schoenoprasum), bog bean/white bog-orchid (Parnassia palustris), whorled lousewort (Pedicularis verticillata), and tufted vetch (Vicia cracca).

The Nature of tidal zone vegetation varies depending on geographical conditions [44]. As noted by A.A. Korchagin [44], marine terrace vegetation is characterized by the following zonal patterns: from north to south, waterlogging decreases, while the number of halophytes, conversely, increases. Of considerable interest is The Use of botanical features to determine the recurrence of tsunamis and the extent of wave-hazard zones. As observations by Miller in 1958 [133] in one of the bays of the southwestern coast of Alaska showed, strips of completely damaged tree stands, fallen trunks, washed-away shrubs, and herbaceous plants stretch along the shores subjected to the onslaught of giant waves in 1954. Traces of previous, even more powerful waves can be found on the coast. Thus, located higher up is a strip of young thickets of poplar, alder, and spruce, the age of which, judging by tree-ring counts, ranges around 14–17 years. Along the upper boundary of this strip, mechanical damage is observed on the trunks of the oldest trees, which can be dated to the same period by dendrometric Methods. This strip, about 60 m wide, marks the destruction zone of the giant wave of 1936. Situated still higher is a strip of dense, mature spruce forests about 600 m wide. At an altitude of about 24 m, it abruptly transitions into primeval spruce forests that are not subject to wave destruction from the sea.

The damage found on the trunks of old trees cast ashore by sea waves makes it possible to date that tsunami to 1850–1853. Consequently, through the analysis of coastal vegetation, wave-hazard zones can be reliably identified.

The distribution of vegetation reflects the duration of floodplain inundation by meltwaters. In the flatlands of the temperate zone in the European part of the former USSR [72, 99], low-lying floodplain areas flooded for a prolonged period (over 50 days) are occupied by structurally simple, unformed communities of hygrophilic forbs, sedges, and hygromesophytic grasses: floating mannagrass (Glyceria aquatica), slender tufted sedge (Carex gracilis), water sedge (C. aquatilis), reflected cup-grass (Beckmannia eruciformis), and reed canary grass (Digraphis arundinacea). Middle floodplain levels are flooded for shorter periods of 20–30 days. Here, complex mesophytic forb-grass communities are widespread: meadow foxtail (Alopecurus pratensis), giant bentgrass (Agrostis alba), timothy-grass (Phleum pratense), mountain clover (Trifolium montanum), and dyer's greenweed (Genista tinctoria). Upper levels and areas distant from the river are flooded for a short period (up to 10 days). They are occupied by sparse herb stands of low-growing floodplain plants: black sedge (Carex nigra), Schmidt's sedge (C. schmidtii), Delavigne's koeleria (Koeleria delavignei), red fescue (Festuca rubra), smooth meadow-grass (Poa pratensis), and others.

Indicators of non-floodplain areas are various groupings of dry-valley meadows, Lichens, and oligotrophic sphagnum mosses that cannot tolerate flooding. The lower limit of the appearance of epiphytic lichens on the bark of trees growing within the floodplain serves as an indicator of the maximum flood level.

The species most resistant to flooding—grey willow (Salix cinerea), white willow (S. alba), almond-leaved willow (S. triandra), Russian willow (S. rossica), and green ash (Fraxinus pennsylvanica)—withstand regular flooding for up to 6 months and irregular flooding throughout the entire year. Resistant to flooding for up to 3–5 months are black alder (Alnus glutinosa), downy birch (Betula pubescens), black poplar (Populus nigra), and narrow-leaved oleaster (Elaeagnus angustifolia); and for up to 3–4 months, purple osier (Salix acutifolia) and Caspian willow (S. caspica). Withstanding flooding for a duration of 1.5–3 months are European aspen (Populus tremula), salt-cedar (Tamarix ramosissima), glossy buckthorn (Frangula alnus), and bird cherry (Padus racemonas/Padus racemosa), among others. Negative indicators of flooding include many conifers, in particular Siberian larch (Larix sibirica), Siberian pine (Pinus sibirica), and Norway spruce (Picea excelsa), among others.

The specific conditions of the floodplain regime also affect the floodplain flora. In the meadows of the Middle Volga, A.P. Shennikov [100] notes A number of varieties exclusively confined to the floodplain: Eleocharis eupalustris var. glaucescens, great-flowered buttercup (Ranunculus polyanthemus) var. wolgensis, and dyer's greenweed (Genista tinctoria) var. latifolia.

Morphological features serve as indicators of periodic flooding. In trees and shrubs growing within the flooded floodplain, trunks and branches are often bent in the direction of the current. Traces of ice damage can be observed on tree trunks. The height of the damage corresponds to the water level during the flood.