The study area is located in the northeastern Apennines between Tuscany and Emilia-Romagna regions (Central Italy, Fig. 1). It encompasses 45 wetlands sites, ranging from 535 m up to 1,470 m a.s.l., partially located in the Foreste Casentinesi National Park and in some Special Areas of Conservation belonging to Natura 2000 network (Appendix I). These wetlands include artificial lakes, small ponds, pools, marshes, and wet meadows. The climate is generally submontane/montane, with mesic temperatures and moderate to heavy rainfall, depending on the elevation. The study area has a temperate oceanic bioclimate at higher elevations and a temperate oceanic-submediterranean bioclimate at lower elevations (Pesaresi et al. 2017). As for geological substrates, there are four main geological formations in the area (Carmignani et al. 2013): three on the Tyrrhenian-facing slopes, with two types of siliceous sandstones, with different percentages of limestone and silty schists (“Macigno del Chianti” and “Macigno del Mugello”), and limestone outcrops (“Alberese”); and one, a sandstone-marly flysch formation (“Marnoso-arenacea”) is widespread in the Adriatic-facing slopes. Other less extensive geological formations are also present (Carmignani et al. 2013).

Our dataset is composed of 123 relevés (N = 109 original; N = 14 published; Lastrucci et al. 2005) concerning plant communities dominated by palustrine species. Data have been collected in the years 2005-2019 following the phytosociological method (Braun-Blanquet 1932). Site names, site abbreviations used in the relevé tables, coordinates, elevation, inclusion in protected areas and references concerning published data, are available in Appendix I. We analysed a matrix of 123 relevés × 164 species using a cluster analysis in R environment (R Core Team 2020), using the chord distance of the function vegdist of ´vegan´ package (Oksanen et al. 2020) and median linkage of the function hclust of ´stats´ package (R Core Team 2020). Data was transformed using the Van der Maarel scale. Plant species names mainly follow the Portal to the Flora of Italy (2022), while the syntaxonomic nomenclature of classes, orders, and alliances follows mainly the Vegetation of Europe by Mucina et al. (2016), and the Italian Vegetation Prodrome (Biondi and Blasi 2015). The names of the syntaxa have been corrected and mutated when necessary in agreement with the 4th edition of the ICPN (Theurillat et al. 2021).

PHRAGMITETUM AUSTRALISSavič 1926nom. corr. (Suppl. Material S1, Table 1, rels 1–8, Group 13 in Fig. 2)(Phragmitetum communisSavič 1926nom. inept.)

Nomenclatural notes: The name reported by Savič (1926) is Phragmitetum communis according the taxon name Phragmites communis Trin. 1820. In the current floras of most countries worldwide (see Euro+Med 2023; POWO 2023) the accepted name of this taxon is Phragmites australis (Cav.) Steud. 1840, therefore we corrected the name in Phragmitetum australisSavič 1926nom. corr.

Phragmites australis forms dense species-poor stands, along submerged and emergent shores of lakes, swamps, pools, ponds, riverbanks, and channels (Landucci et al. 2013). The association is rather widespread in Italy (Landucci et al. 2013). In several wetlands of Central Italy, it seems affected by the die-back syndrome (Lastrucci et al. 2017a). In the study area, P. australis is not very common and we found it only at three sites, where it grows in temporarily submerged conditions. Less dense stands can be interpreted as transitional vegetation towards communities belonging to alliance Glycerio-Sparganion.

SCHOENOPLECTETUM LACUSTRISChouard 1924nom. mut. nov. (Suppl. Material S1, Table 1, rels 9–10, Group 2 in Fig. 2)

(Scirpetum lacustrisChouard 1924nom. inept.)

Nomenclatural notes: The name reported by Chouard (1924: 1136-1137) is “Association à Scirpus lacustris” according to the taxon name Scirpus lacustris L. 1753. Currently Scirpus lacustris is included in the genus Schoenoplectus and its name is Schoenoplectus lacustris (L.) Palla 1888 (Euro+Med 2023; POWO 2023). Therefore, we introduce the new name Schoenoplectetum lacustrisChouard 1924nom. mut. nov.

This association, with a strong pioneer feature, is reported for several habitat types such as on shores of mesotrophic to eutrophic lakes, ponds, or channels, usually growing in deeper water than other types of reed vegetation (Poldini 1989; Landucci et al. 2013; Lastrucci et al. 2019). In the study area, it grows catenal to the association Typhetum angustifoliae. Rarely, Schoenoplectus lacustris forms large dense stands, sometimes accompanied by Schoenoplectus litoralis, which can also reach high cover locally. S. litoralis usually forms stands in slightly to moderate halophilous habitats (e.g., Curcó i Masip 2001; Brullo and Sciandrello 2006), but the presence of this species in the freshwater wetlands of the Northern Apennines was highlighted by Lastrucci and Raffaelli (2006).

TYPHETUM LATIFOLIAE Eggler 1933 (Suppl. Material S1, Table 1, rels 11–14, Group 7 in Fig. 2)

Nomenclatural notes: The name Typhetum latifoliaeNowiński 1930 is actually invalid, as it was originally published not at the rank of association but as a subassociation of the Scirpo-Phragmitetum (see Nowiński 1930); the first validly published name for these communities resulted to be Typhetum latifoliae Eggler 1933.

This association is very common in Italy and develops in several different habitats, such as ponds, lakeshores, banks of slow-flowing streams, deltas, swamps, and channels (Landucci et al. 2013), and it tolerates the summer drying (Šumberová et al. 2011). In the study area, the association forms more or less dense stands around ponds. The association is often very poor in species or even monospecific (Hrivnák 2004; Fernez and Causse 2015). This feature is also confirmed within our study area.

TYPHETUM ANGUSTIFOLIAE Allorge ex Pignatti 1953 (Suppl. Material S1, Table 1, rels 15–17, Group 1 in Fig. 2)

This association is typical of several wetland types on mesotrophic to eutrophic waters, often monospecific or species-poor (Landucci et al. 2013). Though the association is rather common in Italy (Landucci et al. 2013 and references therein), and in Tuscany (Lastrucci et al. 2010a; Mereu et al. 2012; Lastrucci et al. 2017b), it was found only at two sites of our study area, forming stands on flooded soils. According to the ecological features of this association, the surveyed stands appeared monospecific or species-poor.

CARICETUM VESICARIAEChouard 1924 (Suppl. Material S1, Table 1, rels 18–21, Group 6 in Fig. 2)

Large sedge vegetation is not widespread in the study area. We found only one patch, corresponding to a community attributable to Caricetum vesicariae, typical of mesotrophic to eutrophic habitats, permanently flooded for most of the year (Landucci et al. 2013). Within the association, variants typical of marshlands and wet meadows can be often identified (Buchwald 1994; Hrivnák 2004; Lastrucci et al. 2008). In the study area, the association is catenal to communities of the alliance Glycerio-Sparganion (associations Glycerietum fluitantis and Glycerio-Sparganietum), but in some relevés, together with typical marsh plants, also a pool of species typical of wet meadows is present (Agrostis stolonifera, Rumex conglomeratus, Ranunculus repens).

GLYCERIO-SPARGANIETUM NEGLECTI Koch 1926 (Suppl. Material S1, Table 2, rels 1–14, Group 8 in Fig. 2; Fig. 3A)

According to Landucci et al. (2013), this association includes both Sparganium erectum subsp. erectum and S. erectum subsp. neglectum communities. However, a recent genetic study also highlighted a putative intraspecific hybridization among subspecies (Píšová and Fér 2020) The stands dominated by S. erectum s.l. can be attributed to this association (Šumberová et al. 2011; Landucci et al. 2013). S. erectum communities are usually located in the ecological transition between the Phragmition and Glycerio-Sparganion communities, so their attribution to the alliance level is not always univocal (Buchwald 1994; Landucci et al. 2013; Landucci et al. 2020).

In the study area, the association forms dense belts around ponds, developing in habitats with strong fluctuations of water levels, similar to Glycerietum fluitantis or Glycerietum notatae, and less flooded than those occupied by Phragmition communities, justifying our attribution to the alliance Glycerio-Sparganion. At some sites, the association also occurs in trampled and disturbed habitats, hosting species of wet meadows such as Poa trivialis, Ranunculus repens, and Rumex conglomeratus.

GLYCERIETUM NOTATAEKulczyński 1928nom. corr. (Suppl. Material S1, Table 2, rels 15–30, Group 12 in Fig. 2)

(Glycerietum plicataeKulczyński 1928nom. inept.)

Nomenclatural notes: The name reported by Kulczyński (1928) is “Glycerietum plicatae” according the taxon name Glyceria plicata Fr. 1839. Currently the accepted name for this taxon is Glyceria notata Chevall. 1827 (Euro+Med 2023; POWO 2023), therefore we corrected the name in Glycerietum notataeKulczyński 1928 nom. corr.

This association occurs in several habitat types such as riverbanks, channels in arable lands, natural and artificial ponds, and depressions in wet meadows, where it is often in contact with other communities of alliance Glycerio-Sparganion (Landucci et al. 2013).

This association is rather common in Italy (Landucci et al. 2013). Accordingly, in our study area, it represents one of the most widespread vegetation types. It has been generally found around small ponds or watering holes, but it can also develop in less humid and disturbed sites, showing, in this case, a higher floristic richness with species of wet meadows such as Carex hirta, Juncus inflexus, Poa trivialis, and Ranunculus repens.

GLYCERIETUM FLUITANTIS Nowinski 1930 nom. inval. (Suppl. Material S1, Table 2, rels 31–34, Group 4 in Fig. 2)

Nomenclatural notes: The name Glycerietum fluitantis Nowinski 1930 although extensively used in recent times and in the past, must be considered invalid according to the ICPN code (Theurillat et al. 2021) because published as a subassociation and not as association (see Nowińsky 1930). However, this nomenclature issue could not be solved in this study.

According to Landucci et al. (2013), this vegetation type is structurally and ecologically very similar to Glycerietum notatae, but Glyceria fluitans is less tolerant than G. notata to eutrophication and disturbance, leading the association Glycerietum fluitantis to be less common in Italy than Glycerietum notatae. This trend was also found in the study area and we recorded Glycerietum fluitantis at only two sites. Rarely, it forms stands in shallow waters with the presence of Ranunculus trichophyllus, or it is in contact with the association Caricetum vesicariae.

BERULETUM ERECTAERoll 1938nom. corr. (Suppl. Material S1, Table 2, rels 35–39, Group 11 in Fig. 2)

(Beruletum angustifoliaeRoll 1938nom. inept.)

Nomenclatural notes: The name reported by Roll (1938) is Beruletum angustifoliae according to the taxon name Berula angustifolia Mert. & W.D.J.Koch 1826. However this name is a nomen illegitimum. Therefore we corrected the name in Beruletum erectaeRoll. 1938nom. corr.

Berula erecta-dominated stands can be attributed to the association Beruletum erectae, though this species also tends to occur in other communities such as Helosciadietum nodiflori Maire 1924 (Lastrucci et al. 2005; Landucci et al. 2013). The association is typical of mesotrophic streams and channels characterized by slow-flowing waters (Landucci et al. 2013). In the study area, the association was found along two wetlands supplied by small streams. According to the cluster analysis, one relevé previously attributed to Phalarido-Petasitetum hybridi (Lastrucci et al. 2005), was attributed to Beruletum, being interpretable as a transition towards tall herb communities, present at the edge of the wetland.

ELEOCHARITETUM PALUSTRISSavič 1926 (Suppl. Material S1, Table 2, rels 40–48, Group 5 in Fig. 2)

This association is dominated by Eleocharis palustris and shows a typical pioneer behavior, often developing in the wet soils emerging during the dry season (Venanzoni and Gigante 2000). In our relevés, we only found E. palustris subsp. palustris, but in the area, the presence of other subspecies is likely (Lastrucci et al. 2020). This association, typically species-poor, is rather common in Italy (Landucci et al. 2013). Even in our study area, it is one of the most widespread vegetation type, colonizing, often in narrow strips, the muddy areas surrounding the small pools and drinking troughs, often in conditions of disturbance due to the presence of livestock. Our relevés show that the association is catenal to communities of hydrophytes of open waters (Chara vulgaris, Potamogeton nodosus, Ranunculus trichophyllus; see also Viciani et al. 2022) reaching the shallow shores of the pools colonized by Eleocharitetum palustris.

CARICETUM REMOTAE Kästner 1941 (Suppl. Material S1, Table 3, rels 1–9, Group 15 in Fig. 2)

This association is typical of flooded depressions with irregular water regimes and gravely beds such as small streams irrigating the forest roads, and forest springs disturbed by animals (Valachovič and Janovicová 1999). Both shade-tolerant and hygrophilous species are present in the floristic composition of the association, sometimes together with a high cover of bryophytes (Kliment et al. 2008). In the study area, we found the association in humid depressions at the forest margins or in mountain forests, watered by seasonal streams or rainwater. Our relevés show the presence of diagnostic species of the association, such as Carex remota (dominant), Schedonorus giganteus or Brachypodium sylvaticum, as well as several forest species such as Athyrium filix-femina and Ranunculus lanuginosus; hygrophilous species such as Juncus spp. and Galium palustre subsp. palustre; and nitrophilous and shade-tolerant species such as Urtica dioica subsp. dioica.

CARDAMINE AMARA community (Suppl. Material S1, Table 3, rels 10–16, Group 16 in Fig. 2)

Cardamine amara communities have often been attributed to the class Montio-Cardaminetea, sometimes considering it as C. amara community (e.g. Gerdol 1993; Mariotti 1995), attributed to different associations such as Cardaminetum amarae (Rübel 1912) Br.-Bl. 1926 (Braun-Blanquet 1949) or Cardamino-Chrysosplenietum alternifolii Maas 1959. The latter is an association typical of springs surrounded by forests with a partially-closed herb layer, often characterized by a species-rich bryophyte layer (Kliment et al. 2008). However, in the study area, C. amara-dominated stands were rather impoverished in species of Montio-Cardaminetea and they were often found at the edge of ponds and pools, sometimes in contact with aquatic vegetation, especially in some areas where small ditches enter the pools. These stands seem to replace the communities of the alliance Glycerio-Sparganion in semi-shaded habitats. In accordance with Hájková and Hájek (2011), also in our study area, the C. amara communities thrive better in wetter conditions than those belonging to the association Caricetum remotae.

CALTHA PALUSTRIS community (Suppl. Material S1, Table 3, rels 17–19, Group 9 in Fig. 2)

Caltha palustris is a very rare species within the study area. It was found only at two sites, typically along little streams where it forms stands rich in hygrophilous and shade-tolerant species. From a phytosociological and nomenclatural point of view, the syntaxonomic attribution of C. palustris communities is affected by the fact that in the past many infraspecific taxa, currently considered synonyms of C. palustris (e.g., C. laeta Schott, Nyman & Kotschy) were used to define the associations. Our communities show some ecological affinities with those reported by Valachovič and Janovicová (1999) and Kliment et al. (2008) in Central Europe under the name Carici remotae-Calthetum laetae Coldea 1978, typical of muddy alluvia of stream meanders, and small-sized forest springs on the low-elevation mountains of Slovakia. In addition, C. palustris can grow in different habitat types, such as the wet mown meadows of the alliance Calthion palustris (Mucina et al. 2016), including for example the association Chaerophyllo hirsuti-Calthetum palustris Balátová-Tuláčková 1985 (see Balátová-Tuláčková 2000). Nevertheless, the ecological features of C. palustris stands occurring in the study area, which grow in partially shaded habitats along rivulets originating from impluviums and springs, let us classifying our communities to the class Montio-Cardaminetea, where the presence of this species is rather frequent (Hájková and Hájek, 2011). The increasing forest coverage and the disturbance by anthropogenic activities and ungulates are critical factors for the occurrence of this vegetation type.

CARICI OTRUBAE-JUNCETUM INFLEXI Minissale et Spampinato 1985 (Suppl. Material S1, Table 4, rels 1–22, Group 18 in Fig. 2; Fig. 3B)

variant with Juncus effusus (Suppl. Material S1, Table 4, rels 11–16, Group 17 in Fig. 2)

variant with Equisetum palustre (Suppl. Material S1, Table 4, rels 17–22, Group 19 in Fig. 2)

The rushes with Juncus inflexus represent one of the most common types of plant communities in the study area. From a topological point of view, they generally occupy the outer belts of wet areas, frequently disturbed and trampled by livestock, or the humid depressions and lowlands temporarily flooded in winter at the edge of forest vegetation. From a phytosociological point of view, J. inflexus can rarely form communities in marsh environments such as Galio palustris-Juncetum inflexi described for Umbria by Venanzoni and Gigante (2000) or, more usually, wet meadows communities such as Junco inflexi-Menthetum longifoliae Lohmeyer 1953 (e.g., Pedrotti 2008) or Carici otrubae-Juncetum inflexi described from Sicily (Minissale and Spampinato 1985). For their floristic composition, and for the richness of Molinio-Arrhenatheretea species, the high frequency of Carex otrubae, and their ecological characteristics, we attribute our stands to the association Carici otrubae-Juncetum inflexi. This association, as reported by Minissale and Spampinato (1985) for Sicily, is in contact with the communities of the long submerged habitats (Eleocharitetum palustris or Glycerio-Sparganion communities). These communities are also known for southern Tuscany (Lastrucci et al. 2019). The analysis of the rush communities of the study area also shows two different aspects. The first one is represented by rush mixed relevés with the presence of J. effusus, lacking in the original relevés of the Carici otrubae-Juncetum inflexi (see Minissale and Spampinato 1985). The second one is represented by stands developing in depressions with water stagnation or with slight runoff at the edge of the forest. This vegetation type is differentiated by species of shady margins and/or indicators of high water availability, characterizing a more hygrophilous variant of the Carici-Juncetum, with high frequency/cover values of Equisetum palustre, E. telmateja, Mentha aquatica, and the sporadic presence of the rare Epipactis palustris. The two Equisetum species (particularly E. palustre) show sometimes high cover values, becoming the dominant species in this variant.

EQUISETO PALUSTRIS-JUNCETUM EFFUSI Minissale et Spampinato 1990 (Suppl. Material S1, Table 4, rels 23–25, Group 14 in Fig. 2)

This association was described for the higher stretches of an artificial channel in Sicily (Minissale and Spampinato 1990). The association is characterized by the dominance of Juncus effusus and by the presence of a conspicuous pool of wet meadow species of the class Molinio-Arrhenatheretea, but also of species requiring a high water availability such as Equisetum palustre. In the study area, the association was found only at one site on terraces along a stream. The J. effusus community of a recently restored wetland is also provisionally attributed to this association, despite some floristic differences, maybe due to the disturbance caused by restoration works.

HERACLEO TERNATI-PETASITETUM HYBRIDIPedrotti 2008 (Suppl. Material S1, Table 5, rels 1–6, Group 10 in Fig. 2)

We found Petasites hybridus-dominated communities along the main streams of the study area and at the edge of marshes shaded by forest vegetation. In the plain or submontane wetlands of Italy, the association Phalarido-Petasitetum hybridi Schwick 1933 was often reported (Biondi et al. 2004; Pedrotti et al. 2008; Lastrucci et al. 2010b). According to Pedrotti (2008), in the Apennine mountains, the presence, although rare, of Heracleum sphondylium subsp. ternatum (= H. sibiricum subsp. ternatum) in the P. hybridus communities allows to differentiate a new association, i.e. Heracleo ternati-Petasitetum hybridi. At many sites, the communities appear less floristically defined and they can be interpreted as an impoverished aspect of the association. As far as the alliance classification is concerned, the association was originally attributed to Aegopodion podagrariae of the class Galio-Urticetea (Pedrotti 2008). The name accepted by Mucina et al. (2016) for this class is Epilobietea angustifoliae. In the Italian vegetation prodrome (Biondi and Blasi 2015), the name Aegopodion podagrariae is synonymised with Petasition officinalis, which is attributed to the class Galio-Urticetea. In Mucina et al. (2016), the two alliances are instead both accepted and attributed to two different classes, Epilobietea angustifoliae and Mulgedio-Aconitetea, respectively. Moreover, the concept of Petasition officinalis in Mucina et al. (2016) is restricted to Carpathian and Central European areas. For this reason, we consider it appropriate to maintain the attribution of the association to Aegopodion podagrariae.

PEPLIS PORTULA community (Suppl. Material S1, Table 6, rels 1–2, Group 3 in Fig. 2)

The only surveyed therophytic hygrophilous community is represented by Peplis portula stands, occurring only at two sites. In both cases, this community develops on the edge of pools that are dry up during the summer season. This species acts as a differential or dominant species in various associations of the class Isoëto-Nanjuncetea, in the Mediterranean and in Central European areas (Brullo and Minissale 1998; Šumberová and Hrivnák 2013). The almost monophytic stands of the study area can be considered a “basal phytocoenon” according to Poldini and Sburlino (2005) and do not allow any better phytosociological attribution.

We found two additional small communities in the humid soils nearby the tall helophytic vegetation. The first community is a Carex hirta-dominated wet meadow (Suppl. Material S1, Table 4, rel. 26), with presence of hygrophilous species of the class Molinio-Arrhenateretea (Juncus effusus, J. articulatus, Ranunculus repens), and helophytic species (Carex pseudocyperus, Eleocharis palustris, Galium palustre) and forest species (Fragaria vesca, Geranium nodosum, Salix caprea). This small community shows some affinity to the Festuco-Caricetum hirtae O. Bolòs 1962 reported by Carreras et al. (1988), though other authors considered C. hirta a species with a low phytosociological diagnostic value (Tomaselli and Bernardo 2006). In our case, the limited extent of the stand suggests considering this vegetation as a transitional aspect between the more hygrophilous communities of the flooded areas and the nitrophilous and forest communities of the habitats further from the water.

The second community is a stand dominated by Urtica dioica, developing on shaded and deep soil near woody vegetation and reed bed (Suppl. Material S1, Table 5, rel. 7). This species often forms stands on eutrophic and semi-ruderal habitats (Biondi et al. 2004; Lastrucci et al. 2010b, 2010c, sub Urtico dioicae-Sambucetum ebuli (Br.-Bl. in Br.-Bl. et al. 1936) Br.-Bl. in Br.-Bl. et al. 1952) and it plays a role in differentiating a nitrophilous and emerging variant of Phragmitetum (Lastrucci et al. 2017a). In the study area, this vegetation type marks the boundary between the communities of wetland habitats (e.g. Phragmitetum australis) and the surrounding forests.