Vegetation of the "Altipiani di Colfiorito" wetlands (central Apennines, Italy)

The "Altipiani di Colfiorito" catchment basin in central Italy features a wetland system of great interest for conservation, composed of seven plains. Considering that most of the relevés conducted in the past refer to one plain and date back to the 1960s, the research aim was to widen and update the vegetation knowledge in the whole wetland system. Two hundred and thirty-nine phytosociological relevés were carried out using the Braun-Blanquet method. On the basis of cluster analysis of the species data set and phytosociological interpretation, 39 vegetation types were classified, most of which of high conservation interest in central Italy, referred to the Potamogetonetea (6 communities), Bidentetea (2), Phragmito-Magnocaricetea (21), Molinio-Arrhenatheretea (9), and Epilobietea angustifolii (1) classes. The new subassociation Phalaridetum arundinaceae alopecuretosum bulbosi is also described. Twenty-two communities found in the past decades by other authors were confirmed, while 17 were new records for the study area. Ten communities were attributed to four habitats of community interest according to the 92/43/EEC Directive, coded as 3150, 3260, 3270, and 6510. Twenty-four communities were not confirmed (eight of Charetea, Lemnetea minoris, and Potamogetonetea, one of Bidentetea; seven of Phragmito-Magnocaricetea; three of Scheuchzerio-Caricetea fuscae, four of Molinio-Arrhenatheretea and one of Isoëto-Nanojuncetea). Three habitats of community interest (3140, 3170*, and 7230) were not confirmed.


Introduction
Wetlands represent important ecosystems at the European level (Landucci et al. 2015). The central Apennine (Italy) wetland systems of tectonic-karstic basins are important hotspots of plant and animal biodiversity (Ciaschetti et al. 2020), but management abandonment and such anthropic pressures as drainage, water extraction, tillage, and excavations have greatly reduced their extent and worsened their conservation status (Pedrotti 1965(Pedrotti , 1996(Pedrotti , 2019Ballelli et al. 2010;Catorci et al. 2010).
The "Altipiani di Colfiorito" catchment basin hosts one of the most important wetlands of central Italy and is highly worthy of conservation because of its landscape, plant and animal biodiversity, and ecology (Orsomando and Catorci 1998;Renzini 1998;Tardella 2007). This area includes a wetland protected by the Ramsar Convention, an Important Bird Area, three Special Areas of Conservation, and a Special Protection Area of the Natura 2000 network, according to the 92/43/EEC Directive. Since 1995, part of this wetland system has been included in the Parco di Colfiorito, a Regional Park of Umbria. Several authors (e.g. Pedrotti 1965Pedrotti , 1996Pedrotti , 2019Ballelli et al. 2001;Brusaferro et al. 2008;Catorci et al. 2010;Lastrucci et al. 2017aLastrucci et al. , b, 2019a pointed out the modifications of this wetland in the past decades, which have led to the reduction in extension, worsening of conservation status or local extinction of rare and endangered plant communities, some of which deemed habitats of community interest (Biondi et al. 2010). Moreover, this wetland system includes the Habitat "C1.6a Temperate temporary waterbody" that, although is qualified for Least Concern in the European Red List of habitats and, thus, is not deemed threatened at the European level, in Italy has a declining trend in extent and quality (Janssen et al. 2016).
Most of the studies about the vegetation of this district have been conducted at the Palude di Colfiorito, in the central part of the catchment basin, since the 1960s by Pedrotti, who published the vegetation map (Pedrotti 1975) and the related phytosociological relevés (Pedrotti 2019), which date back to the years 1963-1968, along with some new relevés (Pedrotti 2019;Pedrotti and Murrja 2020). Some other relevés at the Palude di Colfiorito have been published by Pedrotti (1979), Buchwald (1992Buchwald ( , 1994, and Lastrucci et al. (2017a). A few relevés are available for the other wetlands (Aleffi and Cortini Pedrotti 1995;Pedrotti 2019).
Considering that the plant sociology of plant communities in the whole system of the "Altipiani di Colfiorito" had never been exhaustively analysed and that most of the relevés conducted in the past refer to the only Palude di Colfiorito and date back to the 1960s, the research goal was to classify the plant communities that compose the vegetation of the wet environments, widening and updating the vegetation knowledge of the wetland system.
In terms of bioclimate, the study area is in the lower supratemperate bioclimatic belt, whose thermotype is lower supratemperate and the ombrotype is lower humid (Pesaresi et al. 2017); the mean annual temperature ranges from 11 to 13 °C and the mean annual precipitation from 1000 to 1100 mm .
The geological substratum is composed of limestones and the plains are covered by lake and marshy deposits, such as gravel, clay, silty clay, and peat (Materazzi and Pieruccini 2001). Soils are deep, hydromorphic, subacid, rich in organic matter, with silty clayey texture and scarce or absent skeleton (Giovagnotti et al. 2003).
The water supply is mainly provided by rainfall, which is maximum in autumn-winter-spring and minimum in summer, while only a small part derives from some torrent waterways and small springs. This rainfall trend determines significant water level fluctuations, namely the increase of the water-covered areas for short periods, followed by their drainage in summer. Swallow holes at the borders of the plains are the only form of natural drainage and are a surface effect of underground karstic phenomena. A hydric system composed of artificial canals and ditches of moderate depth drains water to swallow holes.
The plains are mainly covered by aquatic and marsh vegetation, humid hay meadows, and arable lands, cultivated mainly with wheat, barley, spelt, lentils, and potatoes, alternated with copses of woody hygrophilous vegetation. The areas between the plains and slopes of the surrounding mountains host agricultural land, small mixed woodlands with Quercus cerris and Carpinus betulus and with Q. cerris and Ostrya carpinifolia, hay meadows, and dry grasslands (Orsomando and Pambianchi 2002).

Land use history and anthropic pressure
The study area has a long land use history. Artificial underground drainage systems were built about two thousand years ago by the Romans and, more recently (1458-1464) by the Da Varano Dukes. The latter, called "Botte dei Varano", caused the complete drainage of the Piano di Colfiorito that until then had hosted a lake (Mengozzi 1781;Pedrotti 2019). Between 1492 and 1631 numerous attempts were carried out to drain the Palude di Colfiorito, by excavating and progressively enlarging the swallow holes, digging canals and ditches, but they never succeeded in the complete reclamation of the basin (Sensi 1998;Pedrotti 2019). Even in the last century, the Palude di Colfiorito was subjected to numerous attempts of reclamation to widen the extent of croplands (Lippi-Boncambi 1940;Pettorossi 1968, 1969;Pedrotti 2019). Photographic documentation of the Palude di Colfiorito shows that in the 1940s-early 1950s, this wetland was almost completely flooded during the rainy part of the year, appearing as a lacustrine area surrounded by a belt of Phragmites australis and Schoenoplectus lacustris, and was indeed called Lake of Colfiorito (Brusaferro et al. 2008;Catorci et al. 2010;Pedrotti 2019). The reed was contained by flame weeding to foster the presence of anatids for hunting purposes (Brusaferro et al. 2008). The extent of the coenoses of the Phragmition communis was changeable depending on the water amount and anthropic pressure, whereas, in the outer part of the basin, there was herbaceous vegetation (Pedrotti 2019). The free waters in the central part of the basin in the mid of the reed bed hosted hydrophytic communities characterized by Potamogeton lucens, Nymphaea alba, Persicaria amphibia, and Characeae (Pedrotti 2019).
Between 1964 and 1972, the vegetation of a peat bog, composed of Eriophorum latifolium, Carex panicea, and Juncus subnodulosus communities, along with Magnocaricion elatae communities and part of Ranunculion velutini hay-meadows, were destroyed to plant a poplar (Populus canadensis) cultivation, and then drained, tilled, and subjected to peat mining (Pedrotti 1965(Pedrotti , 1977(Pedrotti , 2019. From the early 1970s, when hunting was prohibited and the periodical flame weeding ceased, to the end of the 20th century, the reed doubled its surface to the detriment of hydrophytic communities and Schoenoplectetum lacustris (Pedrotti 1975;Orsomando 2002;Catorci et al. 2010), while the vegetation of Trifolio-Hordeetalia reduced its extent (Pedrotti 2019).
In the early 1990s, the thresholds of the bulkheads in front of the three main swallow holes were raised, and gaps in the helophytic vegetation were opened near the borders of the basin (Pedrotti 1996). This intervention had the positive effect of limiting the frequency of desiccation events during summer. However, in the last 20 years, the Palude di Colfiorito underwent several times desiccation, probably because of the reduction of precipitation and the increase in evapotranspiration due to the spread of the reed bed (Brusaferro et al. 2008;Catorci et al. 2010).
Since the institution of the Colfiorito Regional Park, the anthropic pressure ceased; however, the reed bed spread, closing some canals and ditches, and accumulated a great amount of litter, causing negative impacts on the wetland ecosystem (Brusaferro et al. 2008;. The Nymphaeetum albae spread as well, and a shrub formation now covers the area formerly covered by the peat bog vegetation (Pedrotti 2019).
Recently, Lastrucci et al. (2019a) recorded at the Palude di Colfiorito a net 18.8% increase in the surface of the reed bed between 1988 and 2012 due to the expansion of the reeds in terrestrial habitats formerly covered by different types of natural vegetation. However, they reported a retreat of the reed bed from the waterfront and an increasing fragmentation associated with the reed dieback process (Lastrucci et al. 2017b(Lastrucci et al. , 2019a. The privately-owned lands occupied by humid hay meadows around the marsh, as well as in the other plains, are traditionally mown twice during the year (late June/ early July and late August). The use of fertilizers in the surrounding arable lands has been deemed as the main cause of water eutrophication in the Palude di Colfiorito, where the quality of water between 2004 and 2011 was frequently considered as poor or bad, with low oxygen concentrations during summer (Regione Umbria 2015).
Finally, we compared the plant communities found in our survey with those found by other authors in the past in the study area and assessed their status as habitats of community interest sensu 92/43/EEC Directive following the Italian interpretation manual of the 92/43/EEC Directive habitats (Biondi et al. 2010).

Results
The cluster analysis of the phytosociological relevés showed the following nineteen main groups (Fig. 2), some of which were further divided into sub-clusters depending on their floristic characteristics: rooting hydrophytic communities dominated by Myriophyllum spicatum, Persicaria amphibia, M. verticillatum, Nymphaea alba (group 1, Suppl. material 1:  Table S19).

Phytosociological interpretation of plant communities
The phytosociological interpretation of plant communities highlighted by cluster analysis (Fig. 2) led to identifying 39 plant communities, described below according to their floristic, phytocoenological, and ecological features. POTAMOGETONO PECTINATI-MYRIOPHYLLETUM SPICATI Rivas Goday 1964 (group 1, Suppl. material 1: Table S1, rels 1-2) Hydrophytic vegetation characterized by the submerged species Myriophyllum spicatum, attributed to the Potamogetono pectinati-Myriophylletum spicati association (Potamogetonion pectinati alliance). This community, generally common in water bodies characterized by a high concentration of organic sediments (Barko and Smart 1986;Ceschin and Salerno 2008), is uncommon in the Palude di Colfiorito, where water depth exceeds 50 cm.
In 1967, Pedrotti found at the Palude di Colfiorito a Myriophyllum spicatum-dominated community, attributed to the Myriophylletum spicati association, which had a localized distribution (Pedrotti 2019).
We found this community of the Nymphaeion albae alliance, in the stagnant waters of the Palude di Colfiorito, with water depth ranging from a few centimeters to 50 cm during the year.
This community, attributed to the Myriophylletum verticillati association (Potamogetonion pectinati alliance), occurs in habitats in an advanced stage of terrestrialization (Šumberová 2011b) and is quite common in stagnant waters of the Palude di Colfiorito (water depth ranging from a few centimeters to more than half a meter). This community was sporadic at the end of the 1960s (Pedrotti 2019). In Italy, this association is uncommon, occurring in Latium (Ceschin and Salerno 2008), Tuscany (Lastrucci et al. 2016), and Sicily (Brullo et al. 1994(Brullo et al. , 2002Raimondo et al. 2000).
NYMPHAEETUM ALBAE Vollmar 1947 (group 1, Suppl. material 1: Table S1, rels 8-10) Species-poor hydrophytic vegetation, dominated by Nymphaea alba, sometimes with Myriophyllum verticillatum and Persicaria amphibia. Following Šumberová (2011a) and Tomaselli et al. (2006), we attributed this community to the Nymphaeetum albae Vollmar 1947 association (Nymphaeion albae alliance). We found this community in the stagnant waters of the Palude di Colfiorito, 0.5-1 m-deep, where it forms very extensive stands. This is consistent with Šumberová (2011a), who stated that this association significantly contributes to water body filling by its high biomass production.
We found this community in stagnant or slowly flowing waters of ditches; toward the banks, it was in contact with the helophytic vegetation of the Helosciadietum nodiflori, Nasturtietum officinalis, and Veronica anagallis-aquatica community.
Pedrotti (2019) found in the outer part of the Palude di Colfiorito, along spring-fed ditches, the Veronico beccabungae-Callitrichetum stagnalis Müller 1962, which differs from our relevés for the presence of Veronica beccabunga and Glyceria fluitans.
In accordance with some Italian authors (e.g. Corbetta and Pirone 1989; Baldoni and Biondi 1993;Venanzoni and Gigante 2000), we did not attribute C. stagnalis-dominated communities to the association Callitrichetum stagnalis Segal 1967, given their low floristic richness.
The association is uncommon in the stagnant or slowly flowing waters along ditches.
The association is widespread in the ditches, in contact with the Nasturtietum officinalis association and the Veronica anagallis-aquatica community. In the sections with slow flowing water, it was found at the border of the watercourse, toward the inside, in contact with the Potamogetono crispi-Ranunculetum trichophylli. Where water is stagnant for most of the year, the community occupies the ditch bed, together with the Caricetum vesicariae and Phalaridetum arundinaceae associations.
In the study area, it occurs along the ditches of the Palude di Colfiorito, near the banks of the deepest ones, where it is in contact with Helosciadietum nodiflori, towards the central part of the ditch section.
We found this community along the main ditch that crosses the Piano di Colle Croce.
The Catabrosa aquatica community found along the River Nera (Marche, central Italy) by Buchwald (1994), which was attributed to the Catabrosetum aquaticae Rübel 1911, should be referred to this association.
The community was found in stagnant or slightly flowing waters, 20-50 cm deep, in contact with Nasturtietum officinalis and the Callitriche stagnalis community.
This community, typical of sunny, quickly to slowly flowing, oligo-to eutrophic waters (Buchwald 1994), is distributed in small stands along the ditches that cross cultivated lands, in contact with Helosciadietum nodiflori, Glycerietum notatae, Callitriche stagnalis community, and Veronica anagallis-aquatica community.
We found this community along a short stretch of a ditch at the Palude di Colfiorito, in contact with Beruletum erectae and Nasturtietum officinalis, where water was 50-60 cm deep.
ELEOCHARITETUM PALUSTRIS Savič 1926 (group 5, Suppl. material 1: Table S5) Single-species or species-poor pioneer plant community, physiognomically characterized by Eleocharis palustris subsp. palustris, sometimes associated with species of the Molinio-Arrhenatheretea class, coming from the surrounding meadows. The community develops where the soil is subject to periodic cycles of submergence and emergence until the end of spring and can tolerate long periods of flooding, but it can also withstand periods with dry soil (Šumberová 2011a).
We found this association in small patches at the edge of Palude di Colfiorito, in contact with communities referred to Phragmition communis and Bidention tripartitae alliances.
The Schoenoplectetum lacustris is in close contact with other associations of the Phragmition communis alliance, especially in the Palude di Colfiorito, and sometimes occupies the whole section of unmanaged ditches.
We found this association inside depressions in the humid meadows and along some ditches of the Piano di Colfiorito.
Typhetum latifoliae occurs in stagnant or slowly flowing waters of marshes and ditches, less than 50 cm deep, in contact with other associations of Phragmito-Magnocaricetea and, to the inside of the basins and ditches, with the hydrophytic coenoses of Potamogetonetea.
It is very common in Italian wetlands (e.g. Martini and Poldini 1980;Corbetta and Pirone 1989;Baldoni and Biondi 1993;Biondi and Baldoni 1994;Buchwald 1994;Biondi et al. 1997;Bracco et al. 2000;Venanzoni and Gigante 2000;Viciani and Raffaelli 2003;Prosser and Sarzo 2004;Ceschin and Salerno 2008;Lastrucci et al. 2010aLastrucci et al. ,b, 2012. CAREX HIRTA community (group 6, Suppl. material 1: Table S6, rels 21-23) Species-poor plant community, with a dominance of Carex hirta. Due to the occurrence of elements of Potentillion anserinae and higher-rank syntaxa, we placed this community in the Potentillion anserinae alliance, even though the presence of some elements of the Phragmito-Magnocaricetea class marks its transition towards the coenoses of flooded habitats. Because of the lack of floristic characterization, we could not classify it at the association level.
Toward the inside of the basins, this community is in contact with helophytic communities of Phragmition communis and Magnocaricion gracilis, and toward the external areas, with Ranunculion velutini meadows.
In Tuscany, Lastrucci et al. (2019b) found a community characterized by Carex hirta and C. otrubae, in fresh, partially shaded and not submerged soils. Biondi and Ballelli (1995) described in Umbria a Carex hirta-dominated association, the Ranunculo acri-Caricetum hirtae, which was found by Ciaschetti et al. (2020)  Species-poor plant community of marshes and ditches, with a dominance of Glyceria maxima, which is associated with other species of the Phragmition communis alliance and higher syntaxa, including Phragmites australis, Phalaris arundinacea, Alisma plantago-aquatica, Sparganium erectum, and Lycopus europaeus.
The community forms more or less extensive stands in the outer part of the Palude di Colfiorito basin, where, according to Pedrotti and Murrja (2020) is reducing its extent, and in small parts of some ditches in other plains, in contact with the associations of the Phragmition communis and Glycerio-Sparganion alliances.
The association is uncommon in the study area and occurs along a short stretch of the main ditch of the Piano di Arvello.
The species composition of this community differs from that of Galio palustris-Juncetum inflexi, described by Venanzoni and Gigante (2000), because of the absence of Galium palustre and Scutellaria galericulata and the prevalence of species of the Molinio-Arrhenatheretea class. It also differs from the Mentho longifoliae-Juncetum inflexi Lohmeyer ex Oberdorfer 1957 asssociation because Mentha longifolia, characteristic of the association, is absent. Because of the dominance of the helophyte Juncus inflexus subsp. inflexus and the presence of Carex otrubae, we attributed this community to the Carici otrubae-Juncetum inflexi, described at Lake Gurrida in northeastern Sicily by Minissale and Spampinato (1985) and found in Calabria (Maiorca et al. 2005) and Tuscany (Lastrucci et al. 2019b).
The association is in contact with some communities of Phragmition communis, i.e. Phalaridetum arundinaceae, Schoenoplectetum lacustris, Glycerietum maximae, and with the humid meadows of the Ranunculion velutini alliance. The other contact vegetation is the Carex otrubae community, toward the banks of some ditches subjected to periodic desiccation.  Table S9) Thermo-heliophilous and nitrophilous association, characterized by Sambucus ebulus, with Urtica dioica and species of the Balloto-Conion maculati alliance and higher syntaxa, such as Conium maculatum, Rubus caesius, Cruciata laevipes, Galium aparine, and ingressive species from Molinio-Arrhenatheretea.
The association occurs sporadically on nitrogen-rich soils, at the edge of roads, paths, and hedges around the wetlands.
This community is very fragmented and forms dense stands in marshy meadows and ditches, in contact with the communities of the Phragmition communis and Magnocaricion gracilis alliances.
Because of the dominance of Cyperus longus and the presence of species of the Phragmito-Magnocaricetea and Molinio-Arrhenatheretea classes, following Landucci et al. (2020), this plant community fits with the Cyperetum longi association (Phragmition communis alliance).
This community is uncommon in the study area, where it forms small and dense stands, in periodically flooded soils, in contact with Phragmitetum australis and the communities of the Ranunculion velutini alliance.
It is the dominant type of vegetation in the Palude di Colfiorito, where it develops in stagnant eutrophic waters with ground flooded from autumn to early summer and not drying in summer. In the other plains, this association occurs in the bed of the ditches.
If it is not subjected to periodic disturbance (mowing or tillage), this community tends to colonize the marshy and humid meadows in the outer vegetation band of the Palude di Colfiorito and the uncultivated lands in contact with the wetland vegetation . Lastrucci et al. (2019a) documented the increasing fragmentation related to the dieback process of the reed bed along the waterfront and the expansion of the reeds in terrestrial habitats formerly occupied by different types of natural vegetation. Phragmites australis is in fact a highly competitive species, which can invade other plant communities in the absence of disturbance. This colonization process was observed for the Carex panicea peaty meadow community, which once had spread over a large area in the south-western part of the Palude di Colfiorito (Pedrotti 1975) and has disappeared as a consequence of competition with Phragmites australis. In fact, relevés carried out in the area formerly occupied by the C. panicea community (Pedrotti 2019), with very rare and interesting species from a biogeographical and conservation viewpoint, such as Dactylorhiza incarnata and Epipactis palustris, were grouped by the cluster analysis among those of Phragmitetum australis, indicating a dynamic stage of vegetation. Nowadays, this area is almost completely invaded by shrubs (Pedrotti 2019).
To the inside of the basin, the community is in contact with the hydrophytic communities of the Nymphaeion alliance, while to the outside of the basin, it is in contact with other Phragmito-Magnocaricetea and Molinio-Arrhenatheretea communities, with which it sometimes forms compenetrations.
The very fragmented stands of this association (sometimes extended a few square meters) occur on the external edge of humid meadows, in contact with croplands.
The very fragmented stands of this association, sometimes extended a few square meters, occur at the edge of marshy and humid meadows, which are flooded until late spring-early summer and emerge in mid-late summer.
Two variants of this association, characterized by Persicaria lapathifolia and Chenopodiastrum murale were found by Pedrotti and Murrja (2020) in the eastern part of the Palude di Colfiorito.
EPILOBIUM HIRSUTUM community (group 12, Suppl. material 1: Table S12, rel. 1) Epilobium hirsutum-dominated nitrophilous community found at the edge of the humid meadows of Ranunculion velutini. Given that most of the species of this community are characteristic of Potentillion anserinae and higher syntaxa, e.g. Ranunculus repens, Galega officinalis, and Lotus corniculatus, we placed it in the Potentillion anserinae alliance.
This community occurs along the banks of ditches at the borders of the plains, periodically flooded during the year, with alternation of a flooding phase in winter and spring and a summer emergence phase. Venanzoni and Gigante (2000) described in the Lakes Trasimeno and Alviano (Umbria) the Cirsio triumfetti-Galegetum officinalis association, placed in the Potentillion anserinae alliance. Compared to that association, our relevés lack Cirsium creticum subsp. triumfettii, Convolvulus sepium, and Lotus tenuis, characteristic species of this association. However, we did not find enough elements to describe a new association. Pedrotti and Murrja (2020) found a similar community in the eastern part of the Palude di Colfiorito and referred it to the Cirsio triumfetti-Galegetum officinalis association; however, in our opinion, this attribution is doubtful be-cause it lacks the characteristic species except C. creticum subsp. triumfettii. DISTANTIS Pedrotti 1976 (group 13, Suppl. material 1: Table S13) Thick-sward wet meadows, dominated by Deschampsia cespitosa. The occurrence of Ranunculus velutinus, Lolium arundinaceum subsp. arundinaceum, Orchis laxiflora, Bellevalia romana, Trifolium resupinatum, and Alopecurus rendlei justifies placing the community in the Ranunculion velutini alliance and the Trifolio-Hordeetalia order. The occurrence of Carex distans, besides Deschampsia cespitosa, allows its attribution to the Deschampsio-Caricetum distantis association, described by Pedrotti (1976) in the nearby Piani di Montelago (Marche).

DESCHAMPSIO-CARICETUM
This community, found in depressions flooded until early summer and moist until the end of summer, is in contact with Hordeo-Ranunculetum velutini meadows, inside which it sometimes forms more or less extended patches, and with communities of the Phragmitetalia and Nasturtio-Glycerietalia orders.
We found the plant community in stagnant waters, 10-50 cm deep, in contact with Phragmitetum australis and Glycerietum maximae.
The association occurs where the soil is frequently flooded from autumn to spring and remains muddy during summer, often in contact with other communities of the Phragmito-Magnocaricetea class.
The prevalence of floristic elements of Potentillion anserinae and higher syntaxa (Potentilla reptans, Rumex crispus, Oenanthe fistulosa, and Thalictrum lucidum) led us to place this community in the Potentillion anserinae alliance.
This community differs in species composition from Rorippo amphibiae-Potentilletum reptantis described in Valdichiana (Tuscany, Italy) by Lastrucci et al. (2010a), because of the absence of Rorippa amphibia, R. prostrata, Bolboschoenus maritimus, and Oenanthe silaifolia; however, there are no elements to describe a new association.
The typical form of this community was found in sites with stagnant eutrophic waters, at the edge of ditches and swallow holes, characterized by seasonal fluctuations, in contact with other helophyitic coenoses of Phragmito-Magnocaricetea to the inside of the basin and the main ditches, and with wet meadows of Trifolio-Hordeetalia, hygro-nitrophilous communities and croplands to the outside.
In the areas where water is drained more rapidly by larger canals to foster the mowing of the surrounding hay meadows, and the soil remains waterlogged and humid for a shorter period, the species composition of the community changes, increasing species from the Molinio-Arrhenatheretea class. The occurrence of this group of species indicates the transition from Phalaridetum arundinaceae to humid meadows of Ranunculion velutini and allows us to describe the new subassociation Phalaridetum arundinaceae alopecuretosum bulbosi, whose differential species are Alopecurus bulbosus subsp. bulbosus, A. rendlei, Oenanthe fistulosa, Trifolium resupinatum, Centaurea jacea subsp. jacea, Galium debile, and Plantago lanceolata.
In small depressions of few centimeters or in contact with marsh vegetation of the Magnocaricion gracilis, where water stands for more time during the year, Carex acuta tends to become codominant with Phalaris arundinacea. We attributed this aspect to a Carex acuta variant of the subassociation Phalaridetum arundinaceae alopecuretosum bulbosi.
CAREX OTRUBAE community (group 19, Suppl. material 1: Table S19, rels 1-5) Species-poor plant community of the stagnant waters dominated by Carex otrubae, present exclusively along the banks of ditches of modest depth, which during the year undergo periods of submergence (winter-early spring) and emergence (summer), depending on the variability of the water supply resulting from rainfall. Carex otrubae communities found by Venanzoni and Gigante (2000) at Lakes Trasimeno and Alviano (Umbria), Minissale and Spampinato (1995) and Brullo et al. (2002) in Sicily, by Cortini Pedrotti et al. (1973) and Pedrotti (1982a) at the Pian Grande of Castelluccio di Norcia (Umbria), attributed to Cypero longi-Caricetum otrubae or Caricetum otrubae, were placed in the Magnocaricion elatae alliance, while Buchwald (1994) placed the Carex otrubae coenoses found at Pian Grande and Pian Piccolo (Sibillini Mountains, Umbria) in the Potentillion anserinae alliance; instead, Lastrucci et al. (2014) attributed the C. otrubae community found at Lake Montepulciano to the Cypero longi-Caricetum otrubae association, in the Mentho-Juncion inflexi. Because of the absence of species of Magnocaricion elatae, and the prevalence of floristic entities of Potentillion anserinae and higher syntaxa (Ranunculus repens, Gratiola officinalis, Carex hirta, and Galium album subsp. album), we considered it more appropriate to place this plant community in the Potentillion anserinae alliance.
The Carex otrubae community is in contact, toward the center of the ditch section, with the Oenantho aquaticae-Rorippetum amphibiae, Carici otrubae-Juncetum inflexi, Glycerietum notatae, and Caricetum vesicariae associations, while toward the external areas, it is in contact with the humid meadows of the Ranunculion velutini.
We found this community inside depressions 20-30 cm deep, surrounded by the humid meadows of Ranunculion velutini alliance.
Because of the different floristic composition and biogeographic contexts, the abovementioned syntaxa do not seem suitable for interpreting the analyzed community; however, there are no elements to describe a new association. Given the high frequencies of species of Potentillion anserinae and the higher syntaxonomic units, we propose placing this community in the Potentillion anserinae alliance. The occurrence of species such as Gratiola officinalis, Ranunculus repens and Rumex conglomeratus indicates an early dynamic stage of this community, which will probably lead to progressive terrestrialization, testified by the Rorippa amphibia community, extremely species-poor and mainly composed of nitrophilous and ruderal species, found at the border of the Palude di Colfiorito by Pedrotti and Murrja (2020).
The plant community develops in stagnant or slowly flowing waters, less than 50 cm deep, in contact with communities of the Phragmition communis alliance. It is indicated in northern and central Italy (e.g. Pedrotti 1977;Baldoni and Biondi 1993;Marchiori et al. 1993;Biondi and Baldoni 1994;Marchiori and Sburlino 1997;Lastrucci et al. 2007;Pedrotti and Murrja 2020).

Changes in the occurrence of the habitats of conservation interest
As far as habitats of community interest are concerned, 19 plant communities found by Pedrotti in the 1960s/1970s can be ascribed to seven habitats of community interest (Suppl. material 2: Table S20). Three of these habitats (3140 -Hard oligo-mesotrophic waters with benthic vegetation of Chara spp.; 3170* -Mediterranean temporary ponds; and 7230 -Alkaline fens) have not been confirmed in our research. In particular, habitat 7230, related to the peat bog, has completely disappeared. In the early 2000s, there was still a residual area characterized by Carex panicea, Epipactis palustris, and Dactylorhiza incarnata (Tardella, pers. obs.), which was invaded by Phragmites australis in the subsequent years (see Suppl. material 1: Table S10, relevés 6-7) and, then, by shrubs (Pedrotti 2019). The habitats that can be confirmed, also in the light of the most recent available relevés are: 3150 -Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation (two communities of the Potamogetonion and two of the Nymphaeion alliances); 3260 -Water courses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation (two communities of the Ranunculion aquatilis); 3270 -Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation (one community of the Bidention tripartitae and one of the Chenopodion rubri); and 6510 -Lowland hay meadows (Alopecurus pratensis, Sanguisorba officinalis) (two communities of the Ranunculion velutini).

Conclusions
We found a considerable richness in plant communities (39 vegetation units, belonging to five vegetation classes). Most of them are of high conservation interest in central Italy because they are endemic to the central and southern Apennines (meadows of the Ranunculion velutini alliance), rare or endangered in peninsular Italy (hydrophytic and helophytic vegetation of Potamogetonetea and Phragmito-Magnocaricetea classes), and deemed habitats of community interest according to the 92/43/EEC Directive. However, we did not confirm 24 plant communities found in the past, most of which can be attributed to habitats of community interest. The studied wetland system underwent several alterations over time and is still threatened by the reduction of precipitation due to climate change, anthropic activities outside or bordering on the basins, such as tillage of croplands, circulation of agricultural vehicles, cropland fertilization that causes eutrophication of the water bodies, and unauthorized water collection for irrigation purposes. The lack or the discontinuity of management and maintenance interventions in part of the study area, especially the lack of management of the reed beds, canals, and ditches, could further negatively impact the biodiversity of the wetland system. The reed expansion to the outside of the basins, the increase in the extent of the Nymphaeetum albae, and the filling of small artificial watercourses is threatening rare species (e.g. Ranunculus ophioglossifolius, R. flammula, Equisetum fluviatile, and Ophioglossum vulgatum, see Ballelli et al. 2010) and fragmenting or substituting plant communities of small extent, such as some hydrophytic and therophytic communities. Moreover, these pressures are exacerbated by the absence of buffer zones covered by meadows between arable lands and wetlands.
To preserve plant species and vegetation diversity of these wetlands, besides the implementation of the usual maintenance activities (cleaning of ditches and mowing of the hay meadows), some conservation actions are advisable, such as the periodical mowing of the reed bed to contain its expansion outwards, and the removal of dead material from the bottom of water pools and canals. Finally, the monitoring of the species composition of plant communities, and of changes in the vegetation mosaic, periodically updating the vegetation maps, is of great importance for the management of the wetland system.