Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River and a new bryophyte habitat for Italy

Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River and a new bryophyte habitat for Italy* Tiberio Fiaschi1, Leopoldo de Simone1, Francesco Mascia1, Ilaria Bonini1,2, Silvia Cannucci1,2, Bruno Foggi3, Matilde Gennai3, Giulio Pandeli3, Simona Maccherini1,2, Emanuele Fanfarillo1,2, Claudia Angiolini1,2 1 Department of Life Sciences, University of Siena, Siena, Italy 2 NBFC, National Biodiversity Future Center, Palermo, Italy 3 Department of Biology, University of Florence, Florence, Italy Corresponding author: Leopoldo de Simone ([email protected]) * Topical Collection: “Conservation and biodiversity of bryophytes in the ecosystems, and community variability”. Edited by Silvia Poponessi, Annalena Cogoni, Marko Sabovljevic, Marta Puglisi. Academic editor: Silvia Poponessi♦ Received 3 November 2025♦ Accepted 9 December 2025♦ Published 22 December 2025 Abstract Riverine habitats play a vital ecological role, offering key ecosystem services, regulating hydrology, and supporting high biodiversity, including species and habitats of conservation concern. This study aimed to identify Annex I habitats under the Habitats Directive (92/43/EEC) within a former protected area along the mid-upper Elsa River (Tuscany, central Italy). From 2021 to 2023, 85 vegetation relevés were collected to classify habitats, map their distribution, and assess major threats. Multivariate analyses revealed 15 Annex I habitats, including 32A0, reported here for the first time in Italy, and three priority habitats (7220*, 91E0*, 91AA*). Habitat 32A0, officially included in Annex I following the accession of Croatia to the EU, shows distinct ecological and structural features compared to habitat 7220*, despite sharing some bryophyte species. While the two often occur in close proximity or form mosaics, habitat 32A0 develops in active waterfalls with constant flow and low carbonate deposition, whereas habitat 7220* forms in slow-dripping areas with high tufa accumulation. The absence of habitat 32A0 from the Italian Habitat Manual underscores the need to revise national habitat classifications to improve identification accuracy and conservation strategies. Our study enhances knowledge of riverine habitats and stresses the importance of adaptive management to safeguard the Elsa River ecosystem. Key actions include continuous monitoring and control of invasive alien species. Incorporating the area into a nearby Special Area of Conservation would strengthen long-term protection in line with the EU Biodiversity Strategy for 2030. Keywords Biodiversity conservation, bryophyte-dominated vegetation, Natura 2000, tufa cascades, urban river, wetland habitats Introduction Rivers are hotspots of biodiversity, hosting a wide assemblage of species and provide irreplaceable services at both the ecosystem and societal levels (Albert et al. 2021; Faghihinia et al. 2021). Riverine habitats are characterised by species that are specifically adapted to fluctuating environmental conditions, such as seasonal changes in water levels, variable nutrient influxes and temperatures. They are often characterized by high levels of biodiversity, including a significant proportion of threatened or community-interest species, which highlights the necessity Vegetation Ecology and Diversity 62 (2025) e176908|DOI 10.3897/ved.176908 Copyright Tiberio Fiaschi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Italian Society of Vegetation Science (SISV) Topical Collection Tiberio Fiaschi et al.: Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River …2 of targeted conservation initiatives (Birk et al. 2020; Graziano et al. 2022). Despite their importance, riverine biodiversity in highly anthropized stretches of rivers is threatened from the direct and indirect effects of anthropogenic activities (Angiolini et al. 2023; de Simone et al. 2025). Urbanization, intensive agriculture, and the spread of both native and alien invasive species, degrade water quality, destabilize soils, and compromise the integrity of the habitats in these areas (Joy and Death 2013; Reid et al. 2019). Moreover, urban expansion often leads to physical changes in the riverine systems such as channelisation and alterations to the course of the riverbed, which in turn reduce soil water absorption, increase flood risk and accelerate erosion (Paul and Meyer 2001; Allan and Castillo 2007). Additionally, intensive agriculture produces nutrient and pesticide pollution, promoting water eutrophication with harmful effects for aquatic life (Bohus et al. 2023; Rivera-Pérez et al. 2023). Climate change further intensifies these pressures by causing more frequent and severe floods and droughts, which disrupt hydrological regimes and threaten specialised species (Schneider et al. 2013; Rivaes et al. 2022; Siddha and Sahu 2022). In this context, the study and preservation of riverine and freshwater habitats is not only ecologically important for biodiversity conservation, but also for the wellbeing of human communities. These habitats, in fact, provide essential ecosystem services, including hydrological regulation, nutrient cycling, and bank stabilisation, as well as serving as refuges for a wide diversity of plant and animal species (Lind et al. 2019; Riis et al. 2020). The protection of these habitats is then essential for the conservation of threatened species, as well as for enhancing ecological resilience. This, in turn, enables adaptive responses to climate change and anthropogenic pressures that threaten ecosystem stability (Reid et al. 2019; Valentim et al. 2024). Within the European Union, the Directive 92/43/EEC, more commonly referred to as the Habitats Directive (HD), demands that Member States identify and protect habitats of community interest and vulnerable ecosystems. The HD highlights the necessity of preserving areas with high ecological value through the Natura 2000 network (Ellwanger et al. 2018; Hödl 2018; Nucci et al. 2022; Spampinato et al. 2023). This regulatory framework recognizes the conservation value and the need for their protection and sustainable management of riverine habitats. Many of these habitats are therefore listed in the HD Annex I under three habitat macrotypes (e.g., macrotypes 3, 7, and 9). This is particularly important in the fragile context of freshwater connected habitats in the Mediterranean basin. Here, rivers are characterised by a high diversity of habitats and species (Stella et al. 2013; Fiaschi et al. 2023), being simultaneously exposed to strong anthropogenic pressures (Cramer et al. 2018; Fernández-Martínez et al. 2020, 2024). Consequently, a significant number of vegetation studies have been conducted in recent years, especially on rivers in central Italy (see Landi et al. 2009; Lastrucci et al. 2012; Angiolini et al. 2017). However, few authors have focused exclusively or even partially on habitats listed in Annex I of the Habitats Directive, highlighting the high vegetation diversity (i.e. Landi et al. 2009; Mereu et al. 2012; Fanfarillo et al. 2023), vulnerability, and significant conservation value of HD habitats found within rivers and streams (Carli et al. 2016; Gigante et al. 2018). To protect biodiversity and designate protected areas, one of the most widely used methods is the assessment of habitats under HD, which is a mandatory action in many cases. Under these premises, this work focuses on a riverine area of high ecological value (Calattini et al. 2025), the mid-upper stretch of the Elsa River (Tuscany, central Italy). The stretch, which flows through the town of Colle Val d’Elsa, has been investigated in terms of its vegetation (Angiolini et al. 1999), while HD habitats remain largely understudied. The only data currently available consist of recent records regarding the presence of some habitats (Rivieccio et al. 2022; Tavilla et al. 2022). Thus, our study firstly aims to provide knowledge on the HD habitats within the boundaries of the Ex ANPIL (Area Naturale Protetta di Interesse Locale) “Parco Fluviale dell’Alta Val d’Elsa” (Siena, Italy), hereafter named Ex-ANPIL-Elsa. This urban stretch of the Elsa River is currently threatened by several anthropogenic pressures, including agriculture, tourism, urbanization, pollution, hydroelectric projects, and water abstraction (Calattini et al. 2025). Hence, providing the necessary tools for a proper assessment of the Ex-ANPIL-Elsa conservation value for its potential inclusion in the Natura 2000 Network is a priority. The main focus of this research will be on riverine habitats, with a focus on evaluating their conservation status, distribution, and identifying the primary threats to their ecological stability. Secondly, the objective is to study the bryophyte-dominated vegetation occurring on the waterfalls along the Elsa River, in order to investigate its possible assignment to one or more habitats, given that these communities are poorly studied in Tuscany. Material and methods Study area The River Elsa is a watercourse in Tuscany (central Italy) that flows through the Val d’Elsa from south to north. It originates in the Montagnola Senese, at an elevation of approximately 580 metres above sea level. It has a length of about 75 km, and its drainage basin covers an area of approximately 867 km2. The Elsa flows through several municipalities, including Colle di Val d’Elsa, Poggibonsi, Certaldo, and Castelfiorentino, before merging into the Arno River. The study area (43°40.5793'N, 11°13.5088'E) is located in central Tuscany (Province of Siena, Italy; Fig. 1A) and is part of the “Parco Fluviale dell’Alta Val d’Elsa”, an ex-protected area designated by the Tuscany Region with Regional Council Resolution no. 256 of 16/07/1997 as an “Area Naturale Protetta di Interesse Locale” (ANPIL). It represents a key ecological corridor within the region, consisting of a riverine ecosystem (Fig. 1B, C) extending Vegetation Ecology and Diversity 62 (2025) e176908 3 along the course of the Elsa River for 7.7 km and covering approximately 203.6 hectares, in the municipalities of Colle di Val d’Elsa (Angiolini et al. 1999). Since the 11th century, the Elsa River has undergone extensive human modifications. Key interventions include the “gore”, artificial channels to divert water toward the town centre for mills, paper mills, forges, and other industries (Gelli 2009; Ulivieri 2017). Expanding agricultural, residential, and industrial infrastructures have exerted pressure on ecosystems, contributing to erosion and habitat fragmentation (Muzzi 1998; Moretti and Soldani 2007). The geology of the Elsa River reflects the interplay between water, tectonics, and erosion, with its deposits representing a significant natural and historical heritage (Barazzuoli et al. 2013). The study area is characterized by travertine deposits, formed by the precipitation of calcium carbonate from CO2-rich waters. These deposits can be classified into thermal travertines, associated with hot springs, and calcareous tufa, typical of fluvial-palustrine environments (Capezzuoli 2013). In addition to travertines, the region features Mesozoic limestones, which form the geological substrate, and alluvial and fluvial deposits composed of sands, gravels, and clays. These sediments, transported and deposited along the active course of the Elsa River, contribute to the geomorphological complexity of the area (Del Zanna 1901; Barazzuoli et al. 2013). Tectonic activity has played a key role in shaping structural depressions and springs, while fluvial erosion has sculpted terraces and steep escarpments. A notable geomorphological feature is the Diborrato waterfall, a 15-meter drop formed by differential erosion of travertine, where some important habitats were found during the field activities (Fig. 1C; Capezzuoli 2013). From a climatic perspective, the macrobioclimate of the study area is Mediterranean, and the bioclimate can be classified as Pluviseasonal oceanic (Mediterranean). The thermotype is upper mesomediterranean (Mediterranean) and the ombrotype is lower humid. From the perspective of continentality, the bioclimate is weak semicontinental (Pesaresi et al. 2017). Meteorological data from a station in the Municipality of Colle di Val D’Elsa, near the study area, recorded an annual average temperature of 13.8 °C, an average temperature of 25.1 °C in the warmest month (August) and 6.9 °C in the coldest month (January) over the period 2000–2024. The mean annual precipitation is 861 mm distributed over 87 days, with rainfall concentrated in autumn and winter, while the summer months (July and August) experience a marked aridity period, despite occasional localized rainfall events (SIR Toscana 2025). Over the centuries, the extent of anthropogenic landscapes has increased, driven by agriculture, residential settlements, and industrial activities, leading to a progressive transformation of the natural environment (Moretti and Soldani 2007). From a conservation point of view, the Ex-ANPIL-Elsa is currently undergoing evaluation for classification under Figure 1. Study area. Location of the study area in Italy (A). Examples of riverine habitats encountered in the Elsa River (B, C). Tiberio Fiaschi et al.: Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River …4 one of the categories outlined in Articles 2 and 6 of Regional Law 30/2015, while the only active protection currently in place is a municipal regulation (Comune di Colle di Val d’Elsa 2021). Vegetation survey Sampling was conducted between 2021 and 2023. The study primarily focused on aquatic and riparian habitats along the River Elsa, extending to adjacent areas including shores, forest fragments, and shrublands within the Ex-ANPIL-Elsa area. A total of 85 relevés were carried out across various HD habitats, using relevés sizes adapted to each habitat type based on the physiognomy, structure, ecology, and extent of the vegetation being studied. In line with the methodological guidelines of Biondi et al. (2009), Angelini et al. (2016), and Gigante et al. (2016), relevés sizes were selected according to the habitat macrotypes identified in the field: for macrotype 3 (standing and running water vegetation), relevés ranged from 2 to 4 m2; for macrotype 5 (shrub vegetation), relevés measured 25 m2; for macrotype 6 (grasslands), 16 m2; for macrotype 7 (spring habitats), relevés measured 0.49 m2 (70 cm × 70 cm) were used; and for macrotype 9 (forest habitats), relevés sizes ranged from 90 to 200 m2 (Chytrý and Otýpková 2003) An exception was made for the HD habitat of waterfalls (belonging to macrotype 3), for which the same relevés size as that used for macrotype 7 habitats was applied. The list of vascular plant and bryophyte species identified within each relevé was recorded, along with the estimated abundance of each species, expressed as visually assessed percentage cover. In addition, information on slope, aspect and water depth were recorded. More precisely, in the field, slope was measured using a digital clinometer, and aspect was measured using a field compass in °deg. For relevés in aquatic environments, water depth was estimated at the centre of each plot by inserting a rod to the bottom and subsequently measuring the wetted section with a measuring tape. Each relevé centre was geo-referenced using a phone GPS with an accuracy ranging from 5 and 10 m. For each relevé, data on elevation was subsequently extracted from the Digital Terrain Model of the study area (Regione Toscana 2025) using the open source sofware QGIS (QGIS.org 2021). To identify the main environmental drivers of the plots assigned to habitats 32A0 and 7220* in the waterfalls along the Elsa River, we measured two additional variables: northness, and water availability. Northness is a variable related to relevés aspect and slope, calculated following Amatulli et al. (2018). Water availability was estimated visually as the percentage proportion of the plot surface covered by flowing or dripping water. Vascular plants were identified according to Pignatti et al. (2017–2019), while mosses were identified according to Cortini Pedrotti (2001, 2005) and liverworts were identified according to Paton (1999). The taxonomic nomenclature follows Euro+Med PlantBase (2025) for vascular plants and for bryophytes. Syntaxonomic nomenclature follows the original authors for associations and sub-associations, Biondi et al. (2014a) for alliances, and sub-alliances, and Mucina et al. (2016) for classes and orders. Data analysis As a first step, the species × relevés compositional matrix (283 species × 85 relevés) was Hellinger-transformed and used to compute a Hellinger distance dissimilarity matrix of relevés with the aim to reduce the importance of species with high cover values (Legendre and Legendre 2012). We applied hierarchical agglomerative clustering (UPGMA) on the Hellinger distance matrix to summarise the compositional structure. To interpret and compare the dendrogram of the resulting relevés clustering, we selected four cluster groups, a number that permitted the best ecological interpretation of sites. The cluster grouping results were subsequently analysed in terms of floristic composition to identify their typical species and HD habitat codes (sensu 92/43/EEC Habitats Directive; Gigante et al. 2016) using both the Italian and European Interpretation Manual of Habitats Directive (Biondi et al. 2009; European Commission 2013); to analyse relevés belonging to the habitat 32A0, given its absence in the Italian Manual, only the guidelines from the European Union’s Habitats Directive (European Commission 2013) were used. Moreover, a Non-metric Multidimensional Scaling analysis (NMDS) based on the same Hellinger distance was performed to represent the relevés in a low-dimensional space by optimising the correspondence between original and in the ordination dissimilarities (Økland 1996). Finally, a Redundancy Analysis (RDA) was performed to measure the ecological differences in the constrained distribution of variance of sites pertaining to bryophyte-dominated HD habitats typical of flowing-dripping waters (habitat 32A0 and 7220*). For this purpose, we used the Hellinger distance dissimilarity matrix of relevés pertaining to habitat 32A0 and 7220*, accounting for the constraining variables slope, northness, water availability and total vegetation cover, to evaluate their role in shaping species composition, habitat structure, and the ecological differentiation between the two habitats. Slope and northness were selected because of their influence in driving riparian plant community composition (de Simone et al. 2025). Water availability was selected for its ability to disentangle habitat 32A0 from 7220* according to European Commission (2013). ANOVA-like permutations were performed to test the global significance of the RDA, its main axes of variation and the effect of each constraining variable (Legendre and Legendre 2012). Results and discussion The cluster analysis allows us to identify four distinct groups of relevés (Table 1), reflecting differences in their floristic composition and ecological characteristics (Fig. 2A). Overall, the clustering results confirm the Vegetation Ecology and Diversity 62 (2025) e176908 5 habitat subdivision carried out in the field based on expert ecological and phytosociological knowledge, although some habitats show strong floristic affinities reflecting their compositional and ecological similarity (Fig. 2A). These cluster groups corresponded to well-defined habitat types regulated by hydrological, structural, and environmental conditions. The first division separates Group 1, consisting of 17 relevés, from all the others. This group, defined as “Communities dominated by bryophytes”, includes relevés attributable to habitats of two different macrotypes (32 Running water, and 72 Calcareous fens), with plant communities pertaining to habitat 32A0 and 7220*, both characterized by a dominance of bryophytes in flowing-dripping water habitats. Their distinct clustering structure suggests that these habitats share a fraction of their species pools and have, to some level, similar specific abundances. Group 2 (27 relevés) includes relevés referable to habitats belonging to the macrogroup 3 (3140, 3150, 3260, and 3290) and named “Aquatic communities dominated by algae and hydrophytic species”. These habitats are all characterized by the presence and dominance of algae of the Characeae family or vascular hydrophytes. Their clustering structure confirms that these habitats are closely related, likely due to shared ecological factors such as standing or slow-moving waters, submerged conditions, and nutrient availability. Moreover, the distinction of aquatic communities dominated by algae and hydrophytic species (Group 2) from the communities dominated by bryophytes (Group 1) underscores their distinct ecological requirements, particularly in terms of water flow and substrate stability. Group 3 (19 relevés) encompasses habitats of macrohabitat 3 and 6 (3270, 3280, 6420, and 6430) and was named “Communities of tall-herb humid meadows”. This cluster group, well divided from the previous two, is characterised by the dominance of herbaceous species colonizing riverbanks and transitional zones between aquatic and terrestrial habitats. Floristic similarities of relevés belonging to this group reflect their shared influence by environmental conditions such as periodic flooding and moisture availability, which shape the composition of these river meadows. Moreover, their intermediate position between aquatic and terrestrial habitats highlights their role as ecotonal communities. Group 4 (22 relevés), named “Communities dominated by woody species,” includes forests and shrub-dominated habitats (macrohabitats 9 and 5; habitats 92A0, 91E0*, 91L0, 91AA*, 5130). These encompass both river woodlands and drier tree or shrub formations that are not directly influenced by the river. The clear separation of this cluster group from herbaceous (Group 3) and aquatic communities (Group 2) suggests a strong ecological differentiation, driven by factors such as substrate stability, soil depth, reduced hydric influence, and long-term successional processes. River woodland habitats (91E0*, 92A0, 91L0) cluster closely together, indicating their shared dependence on riverine conditions, whereas more detached formations (91AA*, 5130) are grouped separately, reflecting their adaptation to less humid and more stable habitats. The NMDS ordination (Fig. 2B), with a stress value of 0.12, is a good representation of relevés dissimilarities. The solution was obtained after 20 random starts, with species scores projected from site scores. The NMDS was able to distinguish the different habitat macrotypes along the aquatic to terrestrial gradient, in accordance with the results of the cluster analysis. All four cluster groups (1– 4) were clearly separated on the first and second axes. In NMDS, the stress value measures how well the ordination represents the observed dissimilarity data in a reduced number of dimensions. Lower stress values indicate a better fit. Along Axis 1, the relevés of Group 1, occurring in flowing or dripping water habitats and dominated by bryophytes, were grouped on the positive side, whereas those of Group 2, found in aquatic habitats, including both lentic and lotic environments, were positioned on the positive side. Along Axis 2, the relevés of Groups 1 and 2, associated with aquatic sites, were mainly grouped on the positive side, together with species such as Hydrogonium bolleanum, Apopellia endiviifolia, Myriophyllum spicatum, and Potamogeton spp.; by contrast, relevés from less humid sites (Group 4) were distributed on the negative side and were characterized by species such as Bromus erectus, Carex flacca, and Juniperus communis. Group 3, with transition habitats (3270, 3280, 6420, 6430) occupy an intermediate position between aquatic and terrestrial habitats, reflecting their ecotonal nature. Their placement in the ordination suggests a decreasing moisture gradient that influences floristic composition. The distribution of groups in both analyses suggests the influence exerted by key riverine environmental factors, such as water depth, flood duration, and hydrodynamic disturbance. For example, habitat 7220* and 32A0, both characterized by a bryophyte-dominated vegetation, are clearly separated from all the others, confirming a peculiar assemblage adapted to high oxygenation and Table 1. Summary of the four main vegetation groups identified by the cluster analysis, with corresponding habitat codes (according to the EU Habitats Directive 92/43/EEC) and the number of relevés per Habitat. Group habitat No. of relevés 1 Communities dominated by bryophytes 32A0 11 7220* 6 2 Aquatic communities dominated by algae and hydrophytic species 3140 6 3150 4 3260 12 3290 5 3 Communities of tall-herb humid meadows 3270 7 3280 5 6420 4 6430 3 4 Communities dominated by woody species 5130 3 91AA* 3 91L0 3 91E0* 8 92A0 5 Tiberio Fiaschi et al.: Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River …6 Figure 2. Results of the clustering and ordination of vegetation relevés. Results of the classification using UPGMA average agglomerative clustering (A). Results of the NMDS ordination (B). NMDS stress = 0.12. Ace.cam = Acer campestre, Adi.cap = Adiantum capillus-veneris, Aeg.pod = Aegopodium podagraria, Aeg.pur = Aegonychon purpurocaeruleum, Aln.glu = Alnus glutinosa, Ane.pip = Aneura pinguis, Bra.rup = Brachypodium rupestre, Bra.syl = Brachypodium sylvaticum, Bro.ere = Bromopsis erecta, Car.fla = Carex flacca, Car. pen = Carex pendula, Cha.vul = Chara vulgaris, Cle.vit = Clematis vitalba, Con.con = Conocephalum conicum, Cra.mon = Crataegus monogyna, Did.top = Didymodon tophaceus, Equ.tel = Equisetum telmateja, Fon.ant = Fontinalis antipyretica, Hyd.bol = Hydrogonium bolleanum, Hym.rec = Hymenostylium recurvirostrum, Jun.com = Juniperus communis, Lig.vul = Ligustrum vulgare, Mel.uni = Melica uniflora, Myr.spi = Myriophyllum spicatum, Pel.end = Pellia endiviifolia, Pel.epi = Pellia epiphylla, Pop.nig = Populus nigra, Pot.cri = Potamogeton crispus, Pot.nat = Potamogeton natans, Pot.nod = Potamogeton nodosus, Pty.pse = Ptychostomum pseudotriquetrum, Que. cer = Quercus cerris, Rub.ulm = Rubus ulmifolius, Sam.nig = Sambucus nigra, Ver.ana = Veronica anagallis-aquatica, Vio.alb = Viola alba. Vegetation Ecology and Diversity 62 (2025) e176908 7 specific hydrological dynamics. Their separation from aquatic habitats dominated by hydrophytes and Characeae (3140, 3150, 3260, 3290) underscores the importance of flow velocity and substrate stability in determining species distribution. Finally, woodland and shrub-dominated habitats relevès of cluster group 4 (91AA*, 91E0*, 91L0, 92A0, 5130) were in the lower right portion of the diagram, clearly separated from aquatic habitats. This distance indicates strong ecological differentiation, with the predominance of woody species adapted to more stable conditions, less directly influenced by fluvial dynamics. Overall, the NMDS confirms the ecological zonation of riparian and aquatic habitats, supporting the classification emerging from the cluster analysis. In the following sections, the communities and HD habitats are described and commented on. Group 1 – Communities dominated by bryophytes 32A0 Tufa cascades of karstic rivers of the Dinaric Alps (Suppl. material 1: table S1) Habitat 32A0, recently added to the European manual following the accession of Croatia to the EU (European Commission 2013), is not yet officially included in the Italian manual, and the plant communities it supports are often misclassified as habitat 7220* – Petrifying springs with tufa formation (Cratoneurion). Nonetheless, Biondi et al. (2014b) hypothesised its presence at the Marmore Falls and in several rivers of Italy. Specifically, these authors noted that the Habitat might be located in mountainous and hilly areas, and in karst zones of the Apennines and the Eastern Alps. This habitat falls under the broader category 32, “Running waters – stretches of watercourses with natural or semi-natural dynamics” and was originally described based on the waterfalls of Plitvice National Park (Topić and Vukelić 2009). Habitat 32A0 is typically found along stretches of rivers undergoing abrupt morphological changes that generate waterfalls, such as those in the Ex-ANPIL-Elsa, where it is quite frequent (Fig. 3). These environments are characterized by dripping and continuous water movement over most of the surface, which exerts physical and chemical stress on the vegetation. The habitat hosts plant communities dominated by bryophytes capable of withstanding strong water pressure, including both liverworts and mosses. Along the Elsa River, the most prevalent species include Fontinalis antipyretica, Apopellia endiviifolia, Rhynchostegium riparioides, and Didymodon tophaceus, all indicated as typical of habitat 32A0 (European Commission 2013). A frequent occurring species is Palustriella commutata, which is also found in habitat 7220*. Mosses display both pleurocarpous and acrocarpous growth forms; the pleurocarpous species, more sensitive to hydraulic force, often grow flattened against the rocky substrate (Glime 2021). The conservation status of this habitat appears generally good, but in a precarious balance, as is the case for many aquatic habitats. Since this is the first record in Italy and given the limited number of scientific studies available, it remains difficult to accurately assess its condition or make systematic comparisons. Figure 3. Diborrato waterfall (Colle di Val d’Elsa, Siena, central Italy), where habitats 32A0 and 7220* are present. Habitat 32A0 occurs in the lateral parts of the image, where more water is present, while habitat 7220* is found in the central, drier area. Tiberio Fiaschi et al.: Riverine ecosystem in central Italy: an insight into EU Habitats of the Elsa River …8 7220* Petrifying springs with tufa formation (Cratoneurion) (Suppl. material 1: table S2) This priority habitat, recognized under the Habitats Directive 92/43/EEC as 7220* develops near springs and on moist rock faces, where extreme environmental conditions support the establishment of distinctive communities dominated by non-vascular plants, particularly bryophytes (Onete et al. 2014; Couvreur et al. 2016). It can be found in a wide range of environments, including forests and open countryside, and is typically associated with the alliance Cratoneurion commutati. These formations are usually small in scale, either point-like or linear, and composed predominantly of hygrophilous and calcicolous mosses and liverworts. Through the absorption of carbon dioxide, these organisms facilitate the precipitation of calcium carbonate from water, leading to the formation of tufa or travertine, a biogenic rock (Couvreur et al. 2016; Denyer et al. 2023). In Italy, habitat 7220* is widespread across nearly all regions, although ecological and distributional studies remain limited. In Tuscany, as in other regions with active bryophyte specialists, it is relatively well documented but still generally underestimated (Rivieccio et al. 2024a). Due to the often small size of habitat patches and the need for specialist bryological knowledge, its identification is particularly challenging and requires both extensive fieldwork and subsequent laboratory analysis. In the Ex-ANPIL-Elsa area, it has been observed on humid rock faces and dripping surfaces, but not in sections with continuous water flow like those which are characteristic of habitat 32A0 (Fig. 3). These plant communities are physiognomically dominated by hygrophilous and calcicolous bryophytes such as Cratoneuron filicinum, Palustriella commutata, Hymenostylium recurvirostrum, Oxyrrhynchium hians, Didymodon luridus, Pellia epiphylla, and Fissidens fontanus, many of which are typical of habitat 7220* according to the European manual (European Commission 2013). Comparison of habitats 32A0 and 7220* and proposal for Elsa River as a 32A0 Site The only previous vegetation study on the Elsa River (Angiolini et al. 1999) focused exclusively on vascular plants and did not record any bryophyte-dominated communities. By contrast, our study identifies two distinct assemblages of non-vascular vegetation, attributable to two different Habitats Directive (HD) types: habitat 32A0 and habitat 7220*. Distinguishing habitat 32A0 from 7220* is challenging both from the ecological and taxonomic standpoints. Through the ecological process of absorption of carbon dioxide from light to continuous dripping waters, which could be also intermittent according to seasonality, the presence of habitat 7220* is often correlated with the abundant formation of tufa or travertine, a biogenic rock. This characteristic is a key ecological element which distinguishes habitat 7220* from habitat 32A0. Conversely, the latter occurs in areas affected by continuous dripping to flowing waters, less affected by seasonality, with a limited formation of biogenic rocks. Considering the taxonomic comparison, habitats 7220* and 32A0 can be confused when only species composition is examined. In fact, according to the Interpretation Manual of European Union Habitats (European Commission 2013), a group of species are characteristic of both habitat 7220* and 32A0, thereby allowing a partial comparative analysis. For this reason, analysing both the local ecological conditions and the composition of bryophytes within the community is mandatory to discriminate between these habitats. Habitat 32A0 includes bryophyte-dominated communities developing on waterfalls and in splash zones, where fast-flowing, aerated water imposes strong physical and chemical stress. These conditions select for specialized mosses and liverworts adapted to frequent submersion and high hydraulic energy like Fontinalis antipyretica, Apopellia endiviifolia, and Rhyncostegium riparioides. By contrast, habitat 7220*, is a priority habitat occurring around springs and dripping calcareous rock faces where water rich in calcium carbonate leads to tufa (travertine) formation. Bryophytes in these communities, such as Cratoneuron filicinum and Hymenostylium recurvirostrum, not only tolerate humid and calcareous conditions but also actively promote carbonate precipitation, contributing to biogenic rock development. The multivariate analysis of our dataset shows a clear separation of the two habitats based on their main environmental drivers (Fig. 4), confirming our interpretation. According to the permutation test, the Redundancy Analysis (RDA) was overall significant (p < 0.01), with only the first constrained axis significant (p < 0.05). The adjusted R2 of the RDA was 0.16, with a cumulative proportion of constrained variance explained by the first two axes of 76.2%. Water availability was the only significant constraint (p < 0.001) with a contribution to the constrained variance of 41.9%. For this reason, our results show that Habitat 32A0 and 7220* have a distinct separation based on hydrological characteristics: while habitat 32A0 develops within active waterfalls with continuous water flow and availability and low carbonate deposition, habitat 7220* is correlated with slow-dripping water and high tufa accumulation. Although similarities in species composition occur (e.g. Palustriella commutata and Eucladium verticillatum), our results show that, at least in the context of the Elsa River, the frequent co-occurrence or mosaic distribution of these habitats makes hydrology and carbonate dynamics critical factors for correct habitat classification. Moreover, species like Pellia epiphylla and Gymnostomum calcareum, characteristic of habitat 7220* relevés in our study area according to the Italian manual, are not listed as indicators for this habitat in the European manual. This discrepancy highlights the critical need for better harmonization between national and EU-level reference documents. Thus, based on our results, we propose recognizing Ex-ANPIL-Elsa as a site hosting habitat 32A0 “Waterfalls with bryophyte communities”, supporting its formal Vegetation Ecology and Diversity 62 (2025) e176908 9 inclusion in Annex I of the Habitats Directive for Italy, in line with the ecological and floristic evidence and the recommendations by Biondi et al. (2014b). Group 2 – Aquatic communities dominated by algae and hydrophytic species Habitat 3140 Hard oligo-mesotrophic waters with benthic vegetation of Chara spp. (Suppl. material 1: table S3) This is one of the few freshwater habitats dominated by green algae belonging to the Characeae family, which form dense underwater meadows (Stefanidis et al. 2019). This habitat is quite common throughout Italy but has been little studied due to the difficulty in species identification (Pagana et al. 2024). According to recent reports from Tuscany, it appears to be present in many areas, both in large lakes and in small ponds (Rivieccio et al. 2024a, 2024b, 2025). This habitat is present within the study area in association with habitat 3150 – Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation, occurring in pools within the dry branches of the Elsa River, as well as in ponds and certain temporary water bodies. Here, some plant communities attributable to this habitat are dominated by Chara vulgaris, a widespread perennial species in freshwater ecosystems that forms submerged meadows, providing essential refuge and foraging areas for numerous aquatic organisms (Schneider et al. 2015). Conversely, other communities are characterized by the dominance of Tolypella glomerata, an annual species adapted to aquatic environments with temporary or limited water levels (Schubert et al. 2024), which is relatively rare within the study area. Notably, Nitella tenuissima was recorded in just one relevé, a species of conservation concern with only a few documented occurrences in Tuscany (Ravera et al. 2024). Overall, within the study area this habitat is highly localized and in poor conservation status, a condition mainly linked to the local morphology and hydrological characteristics rather than to significant anthropogenic pressures. 3150 Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation (Suppl. material 1: table S4) Habitat 3150 includes species-poor plant communities growing in lakes and ponds, with azonal vegetation belonging to the Lemnetea or Potametea classes (Biondi et al. 2012). In Italy and Tuscany, it occurs in most water bodies and is commonly found in areas where it was previously unreported (Tavilla et al. 2022). Within the Ex-ANPIL-Elsa, azonal hydrophytic vegetation associated with this habitat develops in pools adjacent to the river, forming small and species-poor communities. 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Mediterranean Botany 39(1): 3–16. https:// doi.org/10.5209/MBOT.59040 Supplementary material 1 Original vegetation relevés Authors: Tiberio Fiaschi, Leopoldo de Simone, Francesco Mascia, Ilaria Bonini, Silvia Cannucci, Bruno Foggi, Matilde Gennai, Giulio Pandeli, Simona Maccherini, Emanuele Fanfarillo, Claudia Angiolini Data type: xlsx Explanation note: These are the original vegetation relevés used in the manuscript. Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/ odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/ved.176908.suppl1