Ecologica Montenegrina 28: 8-19 (2020) This journal is available online at: www.biotaxa.org/em

Communities of the Bidentetea class of small coastal river valleys of the Western ()

EDYTA STĘPIEŃ1 & STANISŁAW ROSADZIŃSKI2

1Institute of Marine and Environmental Sciences, Faculty of Physical, Mathematical and Natural Sciences, University of , Wąska 13, 71-415 Szczecin, Poland; e-mail: [email protected]; corresponding author 2Department of Plant Ecology and Environmental Protection, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland; e-mail: [email protected]

Received 23 December 2019 │ Accepted by V. Pešić: 4 February 2020 │ Published online 11 February 2020.

Abstract The aim of work was to investigate the diversification, structure, physiognomy and floristic richness of riverside terophytes from Bidentetea tripartitae class in selected coastal river valleys. The investigates area encompassed the lower and middle section of the river valleys of Rega, Parsęta, , Słupia, Łupawa in the (Poland). 68 phytosociological records were made according to the system of Braun-Blanquet. A database was created with the help of the software Turboveg for Windows. The hierarchy classification with the MVSP package was used in order to arrange and group the collected phytosociological data and to single out the types of plant communities. In order to evaluate similarity of samples with respect to species composition the Bray Curtis was calculated and the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) was applied. Three plant communities belonging to one alliance Bidention tripartitae were identified: Bidenti-Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers., Bidentetum cernui Kobendza 1948, community with Polygonum minus, and one plant community belonging to the alliance Chenopodion glauci: Chenopodietum rubri Timar 1947. Given the natural origin of most of the patches, their structure, and the relatively small share of synanthropic species, including alien species, it should be emphasized that they constitute a spontaneous stage of succession of riparian vegetation. The presence of therophyte communities in the valleys of the coastal rivers, as well as their structure and physiognomy, testify to the preservation of their natural character.

Key words: riverside terophytes, riparian vegetation, Natura 2000 habitats.

Introduction

River valleys are often distinguished by abundance of flora and vegetation and are centers of biodiversity on the background of the surrounding landscape (Ward et al. 2002). Riparian zones are under the influence of natural disturbance such as flooding, erosion and sediment deposition, which create dynamic environmental conditions this specific heterogeneous habitat (Naiman & Decamps 1997). Communities of summer-annual pioneer vegetation are one of the components of the riparian zone. The habitats of riverside therophytes are protected as part of the European ecological Natura 2000 network (code 3270) (Borysiak 2004). These are

8 STĘPIEŃ & ROSADZIŃSKI pioneer communities of natural or anthropogenic character which occurs in wet and nutrient-rich habitats such as river banks, muddy alluvial sediments, desiccating oxbows, wet ditches and other man-made habitats (Šumberová & Lososová 2011). The habitats they occupy develop in river valleys during long periods of low water as a result of natural erosion and accumulation processes and are naturally characterized by rapid changes (Borysiak & Stachnowicz 2000). Their optimum occurrence is associated particularly with the low and middle course of large and medium rivers. River regulation combined with straightening and deepening of the river channel and human activities in the river valleys such us land use, recreation, logging, grazing, trampling eliminates habitats of riverside therophyte. Pollution, salification and hyperfertilisation of the habitats results in the recession of particularly sensitive communities, as well as the reshaping of the structure and physiognomy of the remaining phytocenoses (Brzeg & Ratyńska, 1983, Mucina et al. 1993, Richardson et al. 2007). In addition, riverside habitats are highly prone to invasion by alien plants, because of their dynamic hydrology and anthropogenic disturbances (Hood & Naiman 2000). For the full understanding and protection communities of riverside therophytes is necessary to examine the influence of habitat conditions on their state and species composition. The aim of work was to investigate the diversification, structure, physiognomy and floristic richness of riverside therophytes from Bidentetea class in selected coastal river valleys in Western Pomerania.

Study area

The research was carried out within the valleys of coastal rivers of West Pomerania (Figure 1) – the Rega (length 168 km, basin area 2725 km2), Parsęta (length 139 km, basin area 3145 km2), (length 112 km, basin area 683 km2), Słupia (length 139 km, basin area 1620 km2) and Łupawa (length 99 km, basin area 924 km2). They flow mainly through the Szczecin Coastland and Coastland (Pobrzeże Szczecińskie and Pobrzeże Koszalińskie) geographic macroregions in the South Baltic Coastland (Pobrzeże Południowobałtyckie) subprovince and the mesoregions of the Łobez and Polanów Uplands (Wysoczyzna Łobeska and Wysoczyzna Polanowska) in the West Pomeranian Lakeland (Pojezierze Zachodniopomorskie) macroregion of the South Baltic Lakeland (Pojezierze Południowobałtyckie) subprovince (Kondracki 2000).

Figure 1. Map of study area (the north of Western Pomerania, Poland).

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COMMUNITIES OF THE BIDENTETEA CLASS OF OF THE WESTERN POMERANIA

The rivers are classified as small (Bajkiewicz-Grabowska & Mikulski 2017) and carry their water directly to the . They flow from the high slopes of ground and terminal moraines and lake regions, with long stretches taking on the character of foothill rivers with well oxygenated, cold water and a bottom of stones or of stones and sand. Only near the estuaries where they empty into the sea do they acquire the features of lowland rivers with a bottom of sand and silt. Their characteristic feature is an uneven slope, sometimes reaching 2-3‰, and even 5‰ in short stretches. The catchment areas of the coastal rivers are mainly moraine plateaus used for agriculture, built on the surface of moraine clays of low permeability. Compared to rivers of other regions of Poland, fluctuations in water levels and flow are relatively small, which is linked to the high retention capacity of the land, in particular the abundance of lakes and endorheic basins and significant forest cover. The highest flow is usually noted in spring (20-60% more water than the yearly average) and the lowest in July and August, but they do not fall below half the average annual flow (Borówka et al. 2004).

Material and methods

Data sampling. The studies were conducted in summer and autumn in the years 2009–2012. The investigated area encompassed the lower and middle sections of the valleys of small coastal rivers – Rega, Parsęta, Wieprza, Słupia, Łupawa and their tributaries in Western Pomerania (Poland). The relevés placed in the patches of plant communities belonging to the Bidentetea class were performed according Braun-Blanquet (1964) with several additional categories (2m, 2a, 2b) (Barkman et al., 1964) for cover-abundance scale: r (one or few individuals), + (occasional), 1 (abundant and less than 5%), 2m (very abundant and cover about 5%), 2a (5-12.5%), 2b (12.5-25%), 3 (25-50%), 4 (50-75%), 5 (75- 100%). While choosing representative phytocenoses their homogeneity was a criterion taken into account (Matuszkiewicz 1972). 68 relevés were made. A database was created with the help of the software Turboveg for Windows (Hennekens & Schaminee 2001).

Statistical analysis. For a numerical analysis, the quantitative degrees in the Braun-Blanquet scale were transformed into van der Maarel scale (1979): ‘r’ – 1, ‘+’ – 2, ‘1’ – 3, ‘2m’ – 4, ‘2a’ – 5, ‘2b’ – 6, ‘3’ – 7, ‘4’ – 8, and ‘5’ – 9. The hierarchy classification with the MVSP package was used in order to arrange and group the collected phytosociological data and to single out the types of plant communities. In order to evaluate similarity of samples with respect to species composition the Bray Cutris was calculated (Gauch 1982) and the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) was applied (Sneath & Sokal 1973).

Nomenclature of plant species and plant communities. The classification of plant communities was taken from Brzeg & Wojterska (2001). The higher syntaxonomic units (alliances, orders, classes) were done according to Mucina et al. (2016). Vascular plant nomenclature was taken from Mirek et al. (2002) and bryophyte nomenclature was taken from Ochyra et al. (2003).

Results

In the research conducted on the banks of the coastal rivers of West Pomerania, 68 patches of summer therophytes of the class Bidentetea were identified. Based on the numerical classification (Figure 2), four communities belonging to two alliances were distinguished:

Bidentetea Tx. et al. ex von Rochow 1951 Bidentetalia Br.-Bl. et Tx. ex Klika et Hadač 1944 Bidention tripartitae Nordhagen ex Klika et Hadač 1944 Bidenti-Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers. (Group D) Bidentetum cernui Kobendza 1948 (Group C) The community with Polygonum minus (Group A) Chenopodion rubri (Tx. in Poli et J. Tx. 1960) Hilbig et Jage 1972 Chenopodietum rubri Timar 1947 (Group B)

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Figure 2. The numerical classification of relevés from rivers of the Wałcz Plain – dendrogram (1-68 – numbers of relevés; A – comm. with Polygonum minus; B – Chenopodietum rubri Timar 1947; C – Bidentetum cernui Kobendza 1948; Da-Df – Bidenti-Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers).

Bidenti-Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers. (Group D) (Table 1, 2) Physiognomy and structure – was exercised by Polygonum hydropiper (dominated species). Among characteristic species belonging to the class and alliance, very low constancy characterised the following: Polygonum minus, P. mite, P. lapathifolium, Bidens tripartita, B. cernua, Alopecurus aequalis, Rumex

Ecologica Montenegrina, 28, 2020, 8-19 11

COMMUNITIES OF THE BIDENTETEA CLASS OF OF THE WESTERN POMERANIA palustris, Rorippa palustris. In some patches these phytoceonoses are dominated by the neophyte Bidens frondosa. Moss layer was not usually observed in the investigated patches. Group Da – The phytocenoses exercised by Bidens frondosa (dominated species). Among characteristic species belonging to the class and order alliance, very low constancy characterized the following: Polygonum lapathifolium subsp. lapathifolium, Rorippa palustris, Polygonum hydropiper, Polygonum minus, Rumex palustris, and Ranunculus sceleratus with high constancy. There was observed a significant share of species belonging to the class Isoëto-Nanojuncetea (Juncus bufonius, Plantago intermedia, Gnaphalium uliginosum). Species from the Artemisietea vulgaris class also play an important role in patches of Group Da (such us: Urtica dioica, Epilobium roseum, Eupatorium cannabinum). These species pass from adjoining phytocenoses. This phytocenoses was observed only in one river valley (Rega). Habitats – on a flat, thin, sandy shoal covered with aggradate mud which developed on the edges of riparian forests, only one patch was found next to the rush communities complex. Group Db – Meadow species have significant share in these phytocoenoses such as Deschampsia caespitosa, Agrostis stolonifera, Ranunculus repens. Among characteristic species from class and alliances almost only Polygonum hydropiper with high coverage was recorded. Habitats – the patches were observed in shallow depression within anthropogenic coniferous forest in contact with mid-forest meadow fitocoenoses. Group Dc – A low share of characteristic species of Bidentetea class was observed in patches from this group. Species from adjoining phytocoenoses penetrated into the inside of pathes (especialy from Phragmito-Magnocaricetea and Molinio-Arrhenatheretea class). Habitats – The phytocenoses from this group have been observed in several types of habitat. Large group of patches developed at the edge of a footpath trodden by people and in watering places visited by animals. The other group of patches accompanied the outflow of subsoil water and were developing on a very soggy, watery surface. Several patches also developed in shallow terrace depressions filled with the stagnant water. Group Dd – Patches are characterized by considerable share of Bidens frondosa. A relatively high share of species from the class Molinio-Arrhenatheretea was observed (such as Ranunculus repens, Poa palustris, Equisetum palustre, Myosotis palustris). Habitats – on flat slimy river banks, within land depression behind natural levee, and along meander scroll. Group De – Patches belongs to this group are characterized by significant share of characteristic species from Bidentetea class in comparison to other groups. Habitats – on flat river banks of meanders where silt formation process was observed in the soil (black colour of soil surface) Group Df – has an anthropogenic character, patches were found on the ground road with stagnant water in contact with meadow fitocoenoses - hence the significant share of meadow species in patches. Characteristic species from class and alliances are sparsely represented. Floristic richness – floristically rich. In total, 153 plant species were identified in the investigated patches. The number of species in particular relevés varied only from 7 to 29 (average 15 species). Only 6 species belonged to the constancy classes III-V (Polygonum hydropiper, Urtica dioica, Glyceria fluitans, Phalaris arundinacea, Ranunculus repens, Veronica beccabunga). Size – from 1m2 to even 70 m2. Adjoining phytocenoses – rush communities, especially Phalaridetum arundinaceae and Caricetum acutiformis, and less frequently to Glycerietum maximae, Phragmitetum communis, Caricetum gracilis, Typhaetum lalifoliae, Caricetum paniculatae; tall herbs communities, mainly Urtico-Calystegietum sepium, less frequently Eupatorietum cannabini and comm. with Rubus caesius; riparian forests (Alnion incanae); meadow communities (Calthion palustris).

Bidentetum cernui Kobendza 1948 (Group C) (Table 2) Physiognomy and structure – the phytocenoses were based mainly on Bidens cernua, which in one patch was accompanied by Polygonum hydropiper. There was observed a significant share of species belonging to the class Phragmiteto-Magnocaricetea. The surface of one patch was underwater and then there was observed the presence of Lemna minor and there moss layer was absent. In comparison to other patches from investigated rivers the moss layer was significant in relevé No. 49. Floristic richness – not floristically rich. In total, 17 plant species were identified in the investigated patches.

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Table 1. Assotiation Bidenti-Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers. in coastal river valleys of the Western Pomerania (Poland) (Da-Df groups according to the numerical analyses; rivers: B – Bukowina, Ł – Łupawa, P – Parsęta, Ra – Radew, Re – Rega, Są – Sąpólna, Sk – Skotawa, Sł – Słupia, St – Stara Łupawa, Sd – Studnica, U – Ukleja, W – Wieprza; localities: B – Białogórzyno, D – Darnowo, K – Kępice, Ko – Korzybie, Kr – Krzynia, L – Lubuń, O – Osieczki, Os – Oskowo, P – Poganice, R – , S – Starniczki, T – Troszczyno, W – Wrzosowo, Z – Zgojewo, Ż – Żabówko, Że – Żelkowo).

No. of relevé 63 62 46 43 58 54 30 48 47 52 53 20 66 68 67 65 59 39 44 38 37 32 57 61 34 33 31 40 50 36 35 19 56 55 28 27 29 8 24 23 64 22 26 25 21 18 4 5 6 3 2 1

No. of relevé in field

72 71 40 70 36 37 38 35 34 33

263 262 246 243 258 254 221 248 247 252 253 522 524 523 521 259 230 244 229 228 223 257 261 225 224 222 240 250 227 226 256 255 108 107 109 104 103 520 102 106 105 101 Year 10 10 10 10 10 10 10 10 10 10 10 09 12 12 12 12 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 09 10 10 10 10 10 09 10 10 12 10 10 10 10 09 09 09 09 09 09 09 Month 08 08 08 08 08 08 08 08 08 08 08 08 07 07 07 07 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 07 07 07 08 07 07 07 07 07 07 07 08 08 08 08 08 08 08

Day 21 21 19 18 20 20 17 19 19 19 19 26 21 21 21 21 20 18 18 18 18 17 20 20 17 17 17 18 19 18 18 26 20 20 09 09 09 16 08 08 21 08 08 08 08 26 15 15 15 15 15 15 River Sł Sł B Ł Sk Sł Łu B B B B U W W St W Sk Ł Ł Ł Ł St Sk Sk St St St Ł B Ł Ł U Sł Sł P P P Re Ra Ra W Ra Ra Ra Ra U Są Są Są Są Są Są

Locality O O Os P S Kr Że Os Os Os Os T K D D Ko S P P P P Z S S Z Z Z P Os P P T L Kr W W W R B B Ko B B B B T Ż Ż Ż Ż Ż Ż stance 2

Area of relevé (m ) 15 8 5 12 7 8 12 4 3 6 4 10 8 15 7.5 6 7 20 10 20 20 5 5 6 2.5 3 1 9 2 4 5 5 20 20 4 3 3 2 4 6 10 3 8 7 3 3 2 2 2 3.5 2 2 Con Cover total (%) 80 60 60 65 70 80 95 65 65 60 60 85 75 95 90 90 70 70 70 70 75 60 70 60 60 70 60 60 70 70 70 60 60 55 70 70 70 85 60 55 65 90 90 90 75 80 55 65 35 65 90 90 Cover herb layer (%) 80 60 60 65 70 80 95 60 50 60 60 85 75 95 90 90 70 70 70 70 75 60 70 60 60 70 60 60 70 70 70 60 60 55 70 70 70 85 60 55 65 90 90 90 75 80 90 64 35 90 90 90 Cover moss layer (%) 15 20 0 6 0 0 0 10 25 0 0 0 0 1 0 0 0 1 2 1 1 1 0 0 0 1 0 1 1 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 1 0 25 0 0 1 8 1 No. of species 21 9 7 7 13 10 10 20 20 11 10 8 21 18 13 9 10 15 7 7 11 9 19 11 11 9 7 12 7 8 8 9 21 16 12 19 13 13 13 15 10 13 29 28 16 21 22 17 22 27 16 18 I. Ch. Ass. Db Db Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dc Dd Dd Dd Dd Dd Dd De De De De De De De De De De De De Df Df Polygonum hydropiper 4 4 4 4 4 4 5 3 3 3 3 5 4 4 5 4 4 4 4 4 5 3 3 3 4 3 3 3 3 3 3 4 3 3 2a 3 4 3 2b 3 3 3 3 4 3 3 2m 3 2a 1 4 4 V II. Ch. Bidention tripartitae Bidens tripartita . + ...... 2a 2a ...... + . 2a + 3 3 . 2m . . 1 1 2a 2m . 1 II Polygonum mite . . . . + ...... + ...... 1 ...... I Ranunculus sceleratus ...... + 1 2m 2m 1 1 + + . 2a 2a . . I Rumex maritimus ...... 2a ...... + . . 1 + + 1 . . I Bidens cernua . . . . 2m ...... + . r ...... 2m ...... 1 . . 1 . . 1 . . 2a 2m . . I Polygonum minus ...... 2a ...... + . . . . + ...... 1 . . . . . 2m . 1 . 2a + . I III. Ch. D* Chenopodion rubri Atriplex prostrata subsp. latifolia ...... r + ...... + 2m . . 2a 1 + 2a . . I Sporadic species: Chenopodium album* 5 (+); Chenopodium polyspermum 5 (+), 3 (+); Juncus tenageia 48 (+), 47 (2m); Matricaria maritima subsp. inodora* 26 (+). IV. Ch. Bidentetea Bidens frondosa ...... + + 2m + 2a 2a . . . . 2m . . . . . r . . . I Polygonum lapathifolium subsp. lapathifolium ...... 3 ...... 2m 2a 1 1 2a . . I Rorippa palustris ...... + ...... + 1 . + 2a 2m + . + . . 1 . . I V. Ch. Isoëto-Nanojuncetea Juncus bufonius ...... + ...... 1 . . . . . 2m + + + . 2b . 1 1 . 2b I Gnaphalium uliginosum ...... r ...... + . r . + . 1 + . 2a I Sporadic species: Plantago intermedia 26 (+), 1 (+). VI. Ch. Phragmiteteto-Magnocaricetea Veronica beccabunga ...... + + . . . 1 + . 1 + + . . . . + + 2a 2b 2a 2a 2b 3 2b 2m 1 + 2m ...... 1 r 2a 1 ...... III Phalaris arundinacea . . . . 2m 1 + + . . + + . . . 2m . . . . + . 1 1 . . 2a . + . . . . + + + 1 . 1 1 2a 2a 2a 2a . 1 2m 2b 2a 2a . . III Mentha aquatica . . . . + . . + + 2m + 1 + 2m . . + ...... + . + 1 . + . . 1 . . 1 . + 1 + 1 . + ...... II Glyceria fluitans . . 1 . . . . 2m . . . . 1 . . . . + . . . . + . + . . 2b . . . . + + . . 1 2a . . . 2m 2m + + 1 . . + + . . II Veronica anagalis-aquatica ...... + ...... + 2b . . 1 . 2a 2a . 2a 1 1 2m . . + . . . . II Galium palustre 1 + ...... + . . . . 1 + 1 . . . . + ...... 2a 1 . 1 + 1 1 . . . . + ...... II Carex acutiformis ...... 2a 2m + . + ...... + ...... 2m . . . . . + + + . . . I Alisma plantago-aquatica . . . . + 1 1 ...... + ...... + . . . . . 1 . . 2m 1 r . . . 1 . . . I Phragmites australis ...... + ...... 2a . . 2m ...... I Glyceria maxima . . 1 . . . + ...... 1 ...... 1 ...... I Equisetum fluviatile ...... + ...... + 1 ...... I Sparganium emersum ...... + + ...... + . + ...... I Berula erecta . . . . + ...... + ...... r ...... I Sium latifolium ...... + ...... + ...... + . . I Sporadic species: Carex pseudocyperus 18 (1), 3 (+); Cicuta virosa 66 (r); Iris pseudacorus 66 (+); Leersia oryzoides 23 (+); Rumex hydrolapathum 26 (+), 71 (+); Scrophularia umbrosa 34 (1), 18 (r); Scutellaria galericulata 63 (+); Sparganium erectum 67 (+), 22 (2m); Typha latifolia 30 (1).

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COMMUNITIES OF THE BIDENTETEA CLASS OF OF THE WESTERN POMERANIA

TABLE 1. Continued.

No. of relevé 63 62 46 43 58 54 30 48 47 52 53 20 66 68 67 65 59 39 44 38 37 32 57 61 34 33 31 40 50 36 35 19 56 55 28 27 29 8 24 23 64 22 26 25 21 18 4 5 6 3 2 1

VII. Ch. Molinio-Arrhenatheretea Agrostis gigantea . . 1 . . . . 2m 2m . . . 2m ...... 2m 2a 2m 2b 2a + 1 . . . + ...... 1 . . . + . . + . . . . II . Poa trivialis ...... 2b 2b 2m 2b 2m ...... 2b . . . . . 2a ...... I+ Ranunculus repens + 2m . . 1 2m . + + 1 . . + + 1 + + + . + + + 1 2b + . . 1 . . . . 2b 1 2b 2m ...... + + . . . . . + . III. Agrostis stolonifera 2a 2a . . 2m 2b . . . . 2a ...... 2m ...... + . I. Poa palustris ...... 1 ...... 2m ...... 2m 1 2m . . . . . 2a 2a . . . . + . 3 I. Myosotis palustris . . . . . 2a . + + . . . . 1 2m 1 ...... + ...... + . . . 2m + + ...... II. Deschampsia cespitosa 2a 2a + ...... + ...... I. Equisetum palustre + ...... + ...... + ...... + . 1 + . 1 ...... I. Juncus effusus 1 . + 2m . . . + ...... + + . 1 ...... 1 r . . . I. Scirpus sylvaticus 1 ...... + . . . + 2a . . . + . . 1 ...... 1 r ...... I. Caltha palustris . . . . . + . + + + + ...... + . . . + . . . . + . 2m ...... I. Geum rivale + ...... + ...... 1 ...... 1 I. Lysimachia nummularia ...... + ...... + . . 2a ...... I. Lythrum salicaria ...... + ...... + + ...... + ...... I. Sporadic species: Achillea millefolium 26 (+), 21 (1); Alopecurus geniculatus 1 (+); Alopecurus pratensis 22 (2m); Bromus hordeaceus 25 (+), 21 (r); Cardamine pratensis 18 (+); Carex hirta 66 (+); Cirsium oleraceum 56 (+); Crepis paludosa 47 (+); Filipendula ulmaria 63 (+); Holcus lanatus 63 (1); Lotus uliginosus 1 (1); Phleum pratense 1 (1); Poa pratensis 34 (1); Potentilla anserina 1 (1); Potentilla reptans 1 (2m); Ranunculus acris 2 (+); Taraxacum officinale 54 (+), 48 (+); Trifolium repens 4 (+), 1 (+). VIII. Ch. Artemisietea vulgaris Urtica dioica 1 . . . + . + . . . . . 1 2m 1 1 + + 1 + + + + . + + + . . + + + . . . 1 + 1 . . . . 1 1 2a 2a + 2m + 2m + IV . Epilobium roseum ...... 2m + . 1 + + ...... 1 2b 2m 2a 1 . . . . 2a ...... 1 1 . 2m . II. Myosoton aquaticum ...... 2m + 1 + 2m + I. Rumex obtusifolius . . . . + . . . . + . . + ...... + + 1 + + . . . . + . . . . . r . . . . . 1 2m . . . + . + . II. Glechoma hederacea ...... + . . 1 . . . . 1 ...... I. Epilobium parviflorum ...... + + . . + ...... I. Sporadic species: Alliaria petiolata 33 (r); Ballota nigra 18 (r); Calystegia sepium 27 (+); Carduus crispus 48 (+), 47 (+); Cirsium arvense 26 (r), 25 (+); Epilobium hirsutum 27 (r), 26 (+); Equisetum arvense 24 (+); Eupatorium cannabinum 18 (r); Galeopsis bifida 2 (1); Galeopsis pubescens 25 (r); Galeopsis speciosa 39 (+); Galium aparine 27 (1); Geranium robertianum 53 (+), 8 (+); Impatiens parviflora 31 (+); Rubus caesius 43 (+), 2 (1); Symphytum officinale 3 (+). IX. Ch. Papaveretea rhoeadis Stellaria media ...... + . . . . + ...... 2m . 1 . . 1 I. Sporadic species: Polygonum aviculare 1 (2m); Polygonum lapathifolium subsp. pallidum 26 (1), 6 (1); Sonchus asper 2 (+), 1 (+). X. Others Bryum ruderale ...... 2m . . + . I+ Cardamine amara . . . . . + . 2a 2a . 2b 2m + . . . + + 1 + + 2b . . . + . + 1 + . + 1 . . . . . 2m 2a ...... II. Callitriche cophocarpa . . . . . + ...... + + ...... I. Epilobium adenocaulon ...... + ...... + . + ...... + + . + ...... + + . . . . + 2a 2m II2a Festuca gigantea . . + ...... + ...... + . . . . + ...... I. Impatiens noli-tangere + ...... 1 . + . . + + . . + . . . . . + . + + 1 ...... I. Juncus articulatus ...... + ...... + . . 2aI Lemna minor . . . . 2m . 1 ...... + ...... I. Leptobryum pyriforme 2b . . 2a ...... 1 ...... 2b . . . . I. Lycopus europaeus 1 + . . . . . + + 1 . + + . + ...... + ...... 2a ...... + . . . . . II. Oxyrrhynchium hians ...... r . . . r 1 r r r . . . r . . r 1 ...... r . + . . . . II. Plagiomnium undulatum 1 ...... + 1 ...... r r ...... 2m ...... I. Scrophularia nodosa ...... r . + . . . + . I. Solanum dulcamara ...... + 1 ...... + . . + ...... + + . I. Stellaria nemorum . . . 2m + . . + + + . . . + . . . . + + + 1 + 1 + 2m + . . . . + ...... + ...... 2a II. Stellaria uliginosa ...... 1 ...... + ...... r ...... I. Sporadic species: Alnus glutinosa 4 (+); Anthoxanthum odoratum 63 (+); Barbarea vulgaris 25 (+); Brachythecium rivulare 62 (+), 40 (r); Brachythecium rutabulus 4 (+), 2 (+); Calliergon cordifolium 62 (2b); Calliergonella cuspidata 48 (2a), 47 (2b); Callitriche stagnalis 29 (1), 23 (2b); Carex nigra 62 (+); Carex remota 53 (+), 35 (+); Cerastium arvense 2 (+); Ceratodon purpureus 4 (+); Chrysosplenium alternifolium 39 (+), 44 (1); Cratoneuron filicinum 40 (r); Dicranella varia 4 (+); Epilobium adnatum 26 (+); Holcus mollis 43 (2m); Mentha x verticillata 57 (+); Moehringia trinervia 71 (1); Myosotis caespitosa 26 (2a), 25 (1); Oxalis fontana 2 (+); Plagiomnium affine 48 (+), 47 (1); Plantago major 27 (2a); Pohlia bulbifera 3 (1), 1 (1); Pohlia wahlenbergii 2 (2a); Polytrichastrum longisetum 43 (+); Potentilla erecta 63 (+); Sagina procumbens 4 (+), 1 (+); Salis cinerea 4 (1), 6 (+); Salix fragilis 55 (+); Spirodela polyrhiza 30 (1); Vicia tetrasperma 63 (+); Viola palustris 63 (+).

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Table 2. Communities of Bidentetea class in coastal river valleys of the Western Pomerania (Poland) (communities: A – comm. with Polygonum minus, B – Chenopodietum rubri Timar 1947, C – Bidentetum cernui Kobendza 1948, Da – Polygonetum hydropiperis (Miljan 1933) Lohmeyer in R.Tx. 1950 nom invers; other abbreviation are given in Table 1.).

No. of relevé 15 16 14 11 13 12 10 17 9 45 51 42 41 60 49 7 No. of relevé in field 47 48 46 43 45 44 42 49 41 245 251 242 241 260 249 39 Year 09 09 09 09 09 09 09 09 09 10 10 10 10 10 10 09 Month 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 Day 16 16 16 16 16 16 16 16 16 18 19 18 18 20 19 15 River Re Re Re Re Re Re Re Re Re Ł B Ł Ł Sk B Są Locality R R R R R R R R R P Os P P S Os Ż Area of relevé (m2) 8.0 18 2.0 3.0 12.0 17.5 2.5 20.0 2.0 10.0 2.5 20.0 30.0 1.0 2.0 3.0 Cover of herb layer (%) 70 90 75 85 80 75 80 100 90 80 50 85 85 60 90 100 Cover of moss layer (%) 0 0 0 0 10 0 min 0 min 1 0 3 1 0 10 0 No. of species in the relevé 13 16 20 19 25 24 21 17 17 8 8 8 9 9 16 15 I. Ch. Ass. Da Da Da Da Da Da Da Da Da A A A A C C B Polygonum hydropiper . . . . . + ...... + 2a . . Polygonum minus ...... 1 . 1 3 3 5 5 . . . Bidens cernua ...... 4 5 . Polygonum lapathifolium subsp...... 3 . . . . . 5 lapathifolium II. Ch. Bidention tripartitae Ranunculus sceleratus 2b . 1 + + + 1 . r ...... Polygonum mite ...... + . + . . + . . . Rumex maritimus . . + + ...... III. Ch. D* Chenopodion rubri Matricaria maritima subsp. inodora* . . . . . + . . r ...... + Chenopodium polyspermum . r . . . . . + ...... Atriplex prostrata subsp. latifolia . . . . . r . . r ...... Sporadic species: Chenopodium album* 7 (+), Echinochloa crus-galli* 7 (2a), Erysimum cheiranthoides* 13 (+). IV. Ch. Bidentetea Bidens frondosa 3 3 3 2b 3 3 3 5 4 ...... Rorippa palustris . . . 1 . 1 + ...... V. Ch. Isoëto-Nanojuncetea Juncus bufonius + 1 1 1 1 2m 1 ...... Gnaphalium uliginosum . . 2m + + + 1 ...... Plantago intermedia . r . . . . + ...... + Sporadic species: Ricia glauca d 45 (+). VI. Ch. Phragmiteto- Magnocaricetea Glyceria fluitans 1 2m + 1 2a 2m 2m . . . . + . . . . Phalaris arundinacea 1 . 1 . . . 2m 2a 2m . + . . . . . Scrophularia umbrosa . 1 1 1 2a 2a ...... Galium palustre . . . 1 + . . + ...... 2b . Veronica beccabunga 1 . 1 1 . . + ...... + . Mentha aquatica . . . . 2a ...... + 1 . Glyceria maxima ...... + . . . . . 2b + . Veronica anagalis-aquatica 2a . 2m ...... Carex gracilis ...... 1 1 . Berula erecta + + . . + + ...... + . . Sparganium emersum 1 . . . . + ...... Carex acutiformis . . + + ...... Sium latifolium ...... + . + ...... Alisma plantago-aquatica r . . . r ...... + . . Sporadic species: Iris pseudacorus 17 (+), Phragmites australis 14 (+), Sparganium erectum 14 (+). VII. Ch. Molinio-Arrhenatheretea Poa palustris . 1 2m 1 + . 1 2m . 1 . 2m 2m . . 2a Agrostis stolonifera ...... 2b 1 . . 1 . 2m . Ranunculus repens . + . 1 1 + 1 . 1 . 1 . . . . . Myosotis palustris . . + 2b . + ...... + . . Lysimachia nummularia . . . . + . . . . . + . . . . . Sporadic species: Agrostis gigantea 12 (2a), Caltha palustris 49 (+), Cirsium oleraceum 17 (r), Deschampsia cespitosa 49 (+), Equisetum palustre 14 (+), Holcus lanatus 45 (2a), Juncus effusus 10 (1), Lysimachia vulgaris 9 (+), Poa pratensis 51 (2m), Poa trivialis 17 (2a), Rumex crispus 13 (+), Stellaria palustris 49 (+), Trifolium repens 7 (+). VIII. Ch. Artemisietea vulgaris Urtica dioica . 2b . 2a . 2a 2a 2b 2a ...... 2a Epilobium roseum . . . . 2a 2m 2m . 2m ...... Eupatorium cannabinum . + + 1 + . 1 + ...... Carduus crispus . 1 . . r . . + ...... Myosoton aquaticum ...... 1 . + ...... Artemisia vulgaris . . . . . + + . r ...... Rumex obtusifolius . . . . r ...... + Sporadic species: Calystegia sepium 17 (2a), Glechoma hederacea 16 (r), Impatiens parviflora 41 (+), Symphytum officinale 17 (+).

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TABLE 2. Continued. IX. Ch. Papaveretea rhoeadis Stellaria media . . . . 1 r . . . . . + . . . 2a Sporadic species: Apera spica-venti 7 (2m), Fallopia convolvulus 7 (+), Polygonum aviculare 7 (2a), Polygonum persicaria 7 (2m), Vicia hirsuta 7 (+). X. Others Epilobium adenocaulon 1 2a 2m 1 ...... Leptobryum pyriforme . . . . 2a r . . . + ...... Callitriche stagnalis 1 . . . . + + ...... Cardamine amara . . . 2a ...... + . Juncus articulatus . . 1 ...... + . Lycopus europaeus . . + . + + 1 + ...... + . Oxalis acetosella ...... + + + . . . Plagiomnium undulatum ...... + . . . . . 1 . Salix cinerea + . . r ...... Solanum dulcamara . + . . . + ...... Stellaria nemorum . r . . r . . . . . + 1 2m . . . Sporadic species: Atrichum undulatum d 42 (+), Bryum pseudotriquetum 49 (2a), Carex remota 51 (+), Ceratodon purpureus d 42 (1), Chrysosplenium alternifolium 12 (+), Epilobium palustre 49 (+), Festuca gigantea 17 (+), Lemna minor 60 (4), Oxyrrhynchium hians d 9 (+), Plagiomnium affine d 41 (1), Plagiomnium elatum d 49 (1), Pohlia bulbifera d 45 (2m), Polygonum amphibium 13 (+), Quercus robur 13 (r), Scrophularia nodosa 9 (1).

Size – 1 and 2 m2. Habitats – Its patches were developing within the avulsions situated at the edge of peaty meadows, on the surfaces covered with a thick layer of soggy silt. Adjoining phytocenoses – rush communities (Caricetum gracilis, Caricetum paniculatae, Glycerietum maximae) and peaty meadows from Calthion palustris alliance.

The community with Polygonum minus (Group A) (Table 2) Physiognomy and structure – was distinguishable by the significant cover of Polygonum minus in the absence or min cover of other species belonging to the Bidention tripartitae. The cover of Poa palustris and Stellaria nemorum was also considerable. Moss layer was not significant. Floristic richness – floristically poor. In total, 15 plant species were identified in the investigated patches. Size – from 2.5 m2 to even 200 m2. Habitats – in places visited by animals and people on a flat, sandy shoal covered with aggradate mud and especially along the ground roads. Adjoining phytocenoses – rush communities (Phalaridetum), tall herbs communities (Urtico-Calystegietum sepium), anthropogenic forest with Picea abies and Pinus sylvestris).

Chenopodietum rubri Timar 1947 (Group B) (Table 2) Physiognomy and structure – One patch belong to this community. This phytocoenosis has a simplified structure. Physiognomy was distinguishable by the significant cover of Polygonum lapathifolium subsp. lapathifolium. Species from Stellarietea class was observed (such us: Chenopodium album, Echinochloa crus-galli, Apera spica-venti, Matricaria maritima subsp. inodora, Polygonum aviculare). Floristic richness – In comparison to other patches of Bidenteatea class – medium-rich (15 species). Size – 3 m2. Habitats – on sandy flat river bank along the route. Adjoining phytocenoses – tall herbs communities (Urtico-Calystegietum sepium).

Discusion

Phytocoenoses of summer therophytes observed by various authors in river valleys have been both anthropogenic and natural (Geißelbrecht-Taferner & Mucina 1993, Ratyńska 2001, Spałek 2008). Most of the patches (75%) of therophyte communities formed in the study area were of natural origin and were typical of riparian vegetation. They were most often formed on the flat banks of rivers and within alluvia, where there was a layer of fertile silt of varying thickness on the surface of the sandy material deposited by the river. They were dominated by patches of the Bidenti-Polygonetum hydropiperis association. They have been reported from the banks of small watercourses and streams, e.g. by Kępczyński

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(1965) from the Dobrzyń Upland (Wysoczyzna Dobrzyńska) and by Stuchlikowa (1972) from the valley of the River Skawa. An important element of the structure of the patches was species penetrating them from neighbouring phytocoenoses, which was often aided by their small area. Species of the class Phragmiteto- Magnocaricetea played a particularly important role, and to a lesser extent species of the classes Molinio- Arrhenatheretea and Artemisietea vulgaris. Authors such as Kępczyński, Peplińska (1998), and Felzines & Loiseau (2005) have observed a large contribution of species from neighbouring phytocoenoses. Compared to the communities described from large rivers, such as the (Borysiak 2002), (Brzeg & Ratyńska 1983), and Elba (Kiesslich et al. 2003), the patches observed were relatively poor in synanthropic species. In addition, only one patch on the edge of a dirt road was of the alliance Chenopodion rubri, which is represented in large numbers near large rivers. Similarly, Stępień (2010) observed patches of communities belonging only to the Bidention tripartitae alliance in the valleys of small rivers and streams of the Wałcz Plain (Równina Wałecka). Only 25% of the patches owe their origin to human interference. They have developed in the ruts of roads and on the edges of wooded roadsides, in whose depressions water had accumulated after flooding of rivers in the spring, as well as after rainfall. Therophyte communities accompanying roads have been noted by Wawer (1981) and by Fijałkowski & Adamczyk (1990). Therophyte patches have also developed in depressions and paths trodden by people, mainly anglers, near riverbeds and in peatlands. They were also observed on animal trails leading to watering holes and areas rooted by wild boar, where the destruction of the plant cover and the formation of a slight depression relative to the ground surface enabled longer water retention and the appearance of patches of summer therophyte communities (8.8% of the patches were created due to animal activity). Therophyte communities developing at watering holes have also been observed by Harasim (1978). Many authors note the contribution of alien species in patches of summer therophyte communities, especially Bidens frondosa, which has become a common element of therophyte phytocoenoses, influencing their physiognomy and structure. Its occurrence has been reported for years from large rivers (Borysiak 1994, Tokarska-Guzik 2005, Myśliwy 2019), but also from the valleys of small rivers. For example, Ratyńska (2003) observed it on the River Główna, which directly flows into the Warta. The presence of this species in the valleys of coastal rivers is particularly pronounced in the valley of the Rega and its tributaries. Other alien species were rarely recorded. Given the natural origin of most of the patches, their structure, and the relatively small share of synanthropic species, including alien species, it should be emphasized that they constitute a spontaneous stage of succession of riparian vegetation. The presence of therophyte communities in the valleys of the coastal rivers, as well as their structure and physiognomy, testify to the preservation of their natural character.

Conclusions

Contrary to communities from alliance Chenopodion rubri belonging to the class Bidentetea which are situated in the valleys of large rivers or places with anthropogenic pleasure, in the valleys of the small coastal rivers almost exclusively patches belonging to the alliance Bidention tripartitae were recorded. Very important components of the communities surveyed include the species from contact phytocoenoses, especially rush and meadow species. Contrary to the phytocoenoses described from river valleys with stronger antropopressure, synanthropic species as well as alien species played a marginal role in the most of the patches, which proved the natural origin of these phytocoenoses. The presence of Bidens frondosa is particularly pronounced only in the valley of the Rega and its tributaries. The presence of therophyte communities in the valleys of the coastal rivers, as well as their structure and physiognomy, testify to the preservation of their natural character.

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