The Role of Vegetation Monitoring in the Conservation of Coastal Habitats N2000: A Case Study of a Wetland Area in Southeast Sicily (Italy)

1. Introduction

Mediterranean wetlands and their adjacent areas are extremely important for biodiversity and human wellbeing, but their integrity has often been compromised [1]. Fortunately, in recent times, opinion movements and policy actions aimed to wetlands recovery and protection have arisen up [2]. Wetlands are essential ecosystems for preserving animal and plant diversity in the Mediterranean region [3,4]. These biotopes host highly specialized plant communities linked to the substrate type, water quality, flooding time and bioclime, in which grow rare species with specific ecophysiological adaptations [5]. These habitats are disappearing due to human pressure, especially when these regions are subject to land reclamation [6]. This is the case of southern Italy, Sicily and nearby islands, where numerous coastal wetlands have been subjected to severe degradation in recent decades [7 – 10]. In Sicily, coastal wetlands are located mainly in the western, between Trapani and Mazara del Vallo and the south-eastern sectors of the island, and along the coastal strip between Siracusa and Catania. The knowledge about the coastal saltmarsh vegetation in Sicily was investigated by several phytosociological studies [7 – 8, 11 – 18]. In the south-eastern Sicily, the Special Area of Conservation (SAC) “Saline di Priolo” (ITA090013), despite the several environmental changes occurred in the last 70 years, is distinguished by a significant diversity of habitats and plant species. This area includes the Natural Reserve “Saline di Priolo” and comprises different environments, including beach, cliffs, brackish marshes, grasslands, temporary ponds, etc. The SAC “Saline di Priolo”, besides an extensive system of coastal wetlands and salt marshes, also includes the “Magnisi” peninsula, the archaeological sites known as Thapsos and “Biggemi” lagoon. This area is under considerable anthropogenic pressure from nearby industrial activity; in fact, immediately near the protected area rises the Syracuse petrochemical hub. It is a vast industrialized area (the Italian largest petrochemical hub, the second in Europe) created in the 1950s and which extends over an area of forty square kilometers on the east coast of Sicily, including the territory of the municipalities of Augusta, Priolo Gargallo and Melilli up to the gates of Syracuse, and exerting a dramatic environmental pressure on the surrounding territories [19]. As regards the flora and vegetation of the Priolo wetland only few significant investigations have been carried out [13, 17, 20–22]. This study is aimed to provide a comprehensive and updated picture of the flora and fauna present in the area, also including species of conservational interest and alien species, with new insights for future management activities of the territory. A diachronic approach, using mapping and monitoring of the flora, vegetation, and habitat of the Nature Reserve and SAC "Saline di Priolo" over the last 70 years have been carried out, as part of the "MEDISWET" project of the MAVA foundation (Action Activity 7.1.18). Moreover, quantifying the landscape’s spatial structure provides a better understanding of the undergoing impact on ecological processes. In this framework, Landscape Metrics (LM) are an essential tool to analyze the spatial arrangement of the landscape structure over time [23 – 24]. The application of LM is particularly suitable to coastal areas because these landscapes are prone to rapid transformations [25,26]. In summary, the objectives of this research were to: 1. Analyze the structure and floristic composition of the plant communities; 2. Assess the conservation status of the habitats; 3. Analyze the spatiotemporal changes of the wetlands/coastal dune system and assess the loss/reduction of the habitats over the last 70 years.

2. Materials and Methods

The study area is located in the coastal side of the Hyblean plateau (south-eastern Sicily), which is one of the northernmost promontories of the African plate. The Hyblaean plateau (or Hyblaean-Maltese Plateau) is a crust of a continental type isostatically raised and well defined on its edges, different from the other ones in Sicily, and extending south to the Maltese Islands, from which it is separated by a continental shelf [27]. From a floristical point of view, the Hyblean territory hosts a lot of peculiar endemic and rare species, such as, among others, Urtica rupestris Guss., Zelkova sicula Di Pasq., Garfì & Quézel, Trachelium lanceolatum Guss., Anthemis pignattiorum Guarino, Raimondo & Domina, L. pachynense Brullo, Romulea variicolor Mifsud, Elatine macropoda Guss., Solenopsis laurentia (L.) C. Presl. subsp. hyblaea Brullo et al. [28 – 31]. Moreover, it is an area extremely rich in terms of vegetation, hosting a great variety of vegetation types, as well as numerous habitats types according to the Annex I of the 92/43 EEC Directive (or Habitat Directive), including several priority habitat types such as 3170* “Mediterranean Temporary Ponds” [32].

The “Saline di Priolo” SAC extends over 252,5 ha and its perimeter falls within the Priolo Gargallo municipal area. Average annual rainfall is around 500 mm and average annual temperatures arount 18°C [33]. From a bioclimatic point of view, the area under investigation falls within the thermo-Mediterranean zone, with a dry ombrotype [34]

The field surveys were carried out mostly from spring 2021 to autumn 2022, according to the Braun-Blanquet phytosociological approach [35]; these relevés were integrated with other data previously collected in 2008, thus achieving a data set consisting in a total of 128 relevés. Specimens were identified following the second edition of the Flora d’Italia [36 – 39], while the nomenclature of vascular plants follows Portal of the Flora of Italy and subsequent updates [40 – 41], and the regional distribution "rarity" follows Giardina et al. [42]. For vegetation classification and identification of plant communities, a hierarchical clustering was performed by using Euclidean coefficient and beta-flexible algorithm in the program PC-ORD 6 [43]. Syntaxonomic classification follows Biondi et al. [44] and Mucina et al. [45]. Natural vegetational types were classified in habitat types according to the Italian interpretation Manual of the habitats [46]. To evaluate the conservation status of the vegetation and habitat types throughout the last 70 years, a diachronic analysis using aerial ortophotos taken in 1955 and 2015 has been carried out, with the production of vegetation and habitat maps with ArcGis 10.3 software.

Finally, in order to analyze and evaluate vegetation mosaics and changes in spatial arrangement of the landscape structure over the considered timespan, a set of Landscape Metrics (LM) was selected and applied to the two habitat maps (1955 and 2015). Considering the differences in spatial and thematic resolution between the two years of observation, implying a certain level of uncertainty in identifying the single plant associations in the 1955 orthophotos, the landscape metrics were applied to the habitat maps, which have a thematic resolution less detailed than the phytosociological vegetation map. In selecting the most appropriate landscape metrics for the fragmentation assessment in coastal Mediterranean environments, we referred to Cushman et al. [47] and to Tomaselli et al. [25]; a limited set of metrics was selected, and precisely: CA (Class Area), NumP (Number of Patches), MPS (Mean Patch Size), MPAR (Mean Perimeter-Area Ratio), MSI (Mean Shape Index), AWMSI (Area-Weighted Mean Shape Index), and run by using the Patch-Analyst extension of ArcGis.

3. Results and Discussions

The Vascular Flora: Traits Analysis

A total of 304 taxa were recorded, of which 196 for the “Saline di Priolo” and 178 for the Magnisi peninsula (Floristic Appendix 1). Overall, 59 families were recorded, with the most represented being Asteraceae with 15% (45sp.), followed by Poaceae with 13% (39sp.) and Fabaceae with 12% (38sp.). The life forms detected show the typical Mediterranean pattern. In fact, the therophytes, with 123 species, represent 40% of the whole flora, followed by the hemicryptophytes with 31% (94sp.). The percentage of geophytes is also considerable with 13% (39sp.), followed by phanerophytes (16sp.) with 6%, nanophanerophytes (6sp.) with 2% and hydrophytes (4sp.) with 1%. The chorological analysis shows the clear prevalence of the Mediterranean chorotype, that represents 42% of the taxa (129 sp.); whereas the Euro-Mediterranean (62sp.) and Cosmopolitan (33sp.) form respectively 20% and 11% of the flora. The Mediterranean-Turanian and Paleotemperate chorotype follow (each with 14 sp.) with 15%, while the endemic species (6sp.) constitute 2%, which is still relevant considering the limited size of the study area.

Taxa of Relevant Interest

Field surveys highlighted some rare or endemic species (Figure 1), such as Limonium syracusanum Brullo, Ziziphus lotus (L.) Lam., Poterium spinosum L., Bulliarda vaillantii (Willd.) DC., Damasonium bourgaei Coss. (Magnisi peninsula), Teucrium scordium L. subsp. scordioides (Schreb.) Arcang., Limonium narbonense Mill., Euphorbia hirsuta L., and Cressa cretica L. (“Saline di Priolo”).

The most interesting ones are briefly commented in the following paragraphs.

Limonium syracusanum Brullo (Plumbaginaceae)

Suffruticose chamaephyte endemic to the Hyblean Ionian coast, between Augusta and Capo Passero (south-eastern Sicily) [18, 48]. The species characterizes the halophilous phytocoenoses of the rocky coasts of the Crithmo-Limonietea class, together with Crithmum maritimum L. and Arthrocaulon meridionale Es. Ramírez, Rufo, Sánchez Mata, V. Fuente. It is included in the red list of Italian flora [49] with the status of least concern (LC). The species has been observed along the reefs of the north and north-eastern sector of the Magnisi peninsula, near the lighthouse.

Ziziphus lotus (L.) Lam. (Rhamnaceae)

Xerophilous deciduous shrub species with a southern Mediterranean-Saharan range. Reported in the red list of Italian flora [49] with the status of Least concern (LC). In Sicily, the species is rather rare and, in addition to the studied site, it was reported only for the western sector in M. Pellegrino and Mazara del Vallo [42]. Recently, La Mantia and Scuderi [22] gave a more detailed distribution of the species, confirming the location close to “Saline di Priolo”. At regional level, Conti et al. [50] reported this species as vulnerable, while Orsenigo et al. [51] listed it as near threatened (NT). In the Magnisi Peninsula, the species was observed for the first time by Zodda [52]; at present it is represented by a few individuals, limited to a small area on the limestone plateau.

Poterium spinosum L. (Rosaceae)

Thorny chamaephyte with East-Mediterranean distribution. In Italy, the species is present in Apulia, Basilicata, Calabria, Sicily and Sardinia. In Sicily, the species is localized exclusively in the Hyblaean area preferring both carbonate and volcanic substrates [53]. Gargano et al. [54 – 55] classified the species as endangered at the national level (EN). Recently, Orsenigo et al. [51] confirmed the status Endangered (EN) for the Italian territory. In the study area, the species was sporadically observed, along the coast, in the southern part of the peninsula, in the garrigues dominated by Thymbra capitata and Micromeria graeca.

Bulliarda vaillantii (Willd.) DC. (Crassulaceae)

Small therophyte with Mediterranean-tropical distribution. It is an amphibious species typical of Mediterranean temporary ponds (Habitat 3170*: Mediterranean temporary ponds). It is a characteristic species of the annual amphibious communities referable to Lythro hyssopifoliae-Crassuletum vaillantii of the Isoeto-Nanojuncetea class [30]. In Italy it is present in Sicily, Apulia, Basilicata, Lazio, Tuscany, Liguria and Sardinia. In the study area, the species is localized in the small temporary ponds in the central part of the Magnisi peninsula.

Damasonium bourgaei Coss. (Alismataceae)

Rooting hydrophyte with an Atlantic-Mediterranean distribution. Annual species typical of Mediterranean temporary ponds, growing on carbonate and volcanic substrate [56]. It characterizes the annual amphibious communities of the Isoeto-Nanojuncetea class (Habitat 3170*: Mediterranean temporary ponds). In Italy it is present in Apulia, Basilicata, Sardinia and Sicily. D. bourgaei was reported for various coastal sites of Sicily, but at present it can be considered quite rare [30]. In the Magnisi peninsula the species is rather localized.

Teucrium scordium L. subsp. scordioides (Schreb.) Arcang. (Lamiaceae)

Scapose hemicryptophyte with a Euro-caucasican to NW Africa distribution range. It typically grows on wet meadows, where it forms hygrophilous communities together with Juncus subulatus Forssk., Lotus corniculatus L. subsp. preslii (Ten.) P.Fourn., Phyla nodiflora (L.) Greene and Potentilla reptans L.. In Sicily it is threatened by the reduction of its natural habitat [42]. In the study area “Saline di Priolo” it is very localized.

Limonium narbonense Mill. (Plumbaginaceae)

Rosulated hemicryptophyte with Euri-Mediterranean distribution. Perennial halophilous species typical of the coastal saltmarshes. This species together with other halophytes, such as Arthrocaulon meridionale Es. Ramírez, Rufo, Sánchez Mata, V. Fuente, Salicornia perennis Mill. subsp. alpini (Lag.) Castrov., Halimione portulacoides (L.) Aellen, characterizes the perennial halophilous vegetation belonging to Salicornietea fruticosa Br.-Bl. & Tx. ex A. Bolòs y Vayreda & O. de Bolòs 1950 class [57]. In the “Saline di Priolo” L. narbonense is quite common.

Euphorbia hirsuta L. (Euphorbiaceae)

Rhizomatous geophyte with Mediterranean-Macaronesian distribution. The species mainly grows in wet meadows. In the Saline di Priolo, it thrives together with Teucrium scordium L. subsp. scordioides (Schreb.) Arcang., Lotus corniculatus L. subsp. preslii (Ten.) P. Fourn., Phyla nodiflora (L.) Greene and Potentilla reptans L.. In the Saline di Priolo, the species is very localized, on the edges of small wet areas in contact with Tamarix africana. In the last 50 years the species has undergone a strong reduction of its range along the Sicilian coast, in fact today there are few areas where the species is conserved [42].

Cressa cretica L. (Convolvulaceae)

It is a thermo-cosmopolitan halophilous species growing on sandy or muddy saline habitats [58]. In the study area, the species is rare due to reduction or alteration of its natural habitat (1310 “Salicornia and other annuals colonizing mud and sand”). Cressa cretica, together with other annual succulent plants with a summer cycle, characterizes the Cressetum creticae, halo-subnitrophilous and termophilous vegetation colonizing abandoned fields after farming on clayey and salty soils [8]. According to Oresenigo et al. [51], it is classified as "endangered" (EN) in Italy.

Figure 1. Photo plate illustration of some species of the “Saline di Priolo” SAC: (A) Limonium syracusanum; (B) Poterium spinosum; (C) Ziziphus lotus; (D) Damasonium bourgaei; (E) Euphorbia hirsuta; (F) Bulliarda vaillantii; (G) Convolvulus soldanella; (H) Limonium narbonense.

Figure 1. Photo plate illustration of some species of the “Saline di Priolo” SAC: (A) Limonium syracusanum; (B) Poterium spinosum; (C) Ziziphus lotus; (D) Damasonium bourgaei; (E) Euphorbia hirsuta; (F) Bulliarda vaillantii; (G) Convolvulus soldanella; (H) Limonium narbonense.

Plant Communities Description

A total of 28 plant communities (7 annuals and 21 perennials) belonging to 18 phytosociological classes has been identified by cluster analysis (Appendix 2, Table S1).

4. Coastal Dunes Vegetation (Figure 2,4)

The psammophilous vegetation immediately adjacent the aphytoic belt is characterized by annual herbaceous communities ascribable to the association Salsolo-Cakiletum maritimae Costa & Manzanet 1981 nom. mut. propos. in Rivas-Martínez et al. 2002 (habitat 1210 “Annual vegetation of drift lines”). On the embryonic dunes it is possible to distinguish two different associations: the first one is the perennial herbaceous vegetation of the Cypero capitati-Agropyretum juncei Kühnholtz-Lordat (1923) Br.-Bl. 1933, with the dominance of Thinopyrum junceum (habitat 2120 “Embryonic shifting dunes”); the second one is the Sileno coloratae-Ononidetum variegatae Gèhu & Gèhu-Franck 1986, annual vegetation characterized in particular by Ononis variegata and Silene niceensis (habitat 2230 “Malcolmietalia dune grasslands”). In the backdune, where the substrate is more stable and richer in organic matter, a chamaephytic vegetation occurs, the Centaureo sphaerocephalae-Ononidetum ramosissimae Br.-Bl. e Frei in Frei 1993. In Sicily, these psammophilous communities are quite widely represented [15 – 16, 18, 59], although their bad conservation status.

Figure 2. Cluster analysis of coastal dunes communities. Plant communities: 1. Cypero capitati-Agropyretum juncei; 2. Centaureo sphaerocephalae-Ononidetum ramosissimae; 3. Sileno coloratae-Ononidetum variegatae.

Figure 2. Cluster analysis of coastal dunes communities. Plant communities: 1. Cypero capitati-Agropyretum juncei; 2. Centaureo sphaerocephalae-Ononidetum ramosissimae; 3. Sileno coloratae-Ononidetum variegatae.

5. Rocky Coasts Vegetation (Figure 3,4)

The coastal rocky outcrops of the Manghisi peninsula are colonized by halophytic communities belonging to the classes Salicornietea fruticosae, Crithmo-Staticetea and Saginetea maritimae. The first belt closest to the sea and subjected to salt spray, as well as the brackish rocky pools periodically inundated behind the cliffs, are home to a vegetation dominated by Arthrocaulon meridionale, a succulent chenopod shrub usually linked to seasonally inundated salt marshes, and by Limonium virgatum and Limbarda crithmoides. This vegetation is atributable to the Limonio virgati-Arthrocnemetum macrostachyi, an association belonging to the class Salicornietea fruticosae, described by Biondi et al. [60] from southern Apulia and already reported for Sicily by Minissale and Sciandrello [16] and by Sciandrello et al. [18]. Immediately inwards follows the Limonietum syracusani (habitat 1240 “Vegetated sea cliffs of the Mediterranean coasts with endemic Limonium spp.”), perennial association of the Crithmo-Staticetea and dominated by Limonium syracusanum and Crithmum maritimum, with a few other halophilous/subalophilous species. On corroded surfaces, more or less flat, with thin soil, subjected to disturbance, a prostrate perennial vegetation dominated by Lotus cytisoides and Frankenia hirsuta develops, taking the place of the Limonietum syracusani. The subhalophilous ephemeral communities characterized by small therophytic, xerophilous plants with a short spring cycle growing in the small limestone rocky pools covered by a thin layer of sandy-loamy soil rich in salts and nitrates and periodically interested by salt water, are here referred to the Parapholido incurvae-Spergularietum marinae, new association here described (Rel.2,Tab.1) characterized by the dominance of Parapholis incurva and Spergularia marina (=S. salina), and belonging to the Sileno sedoidis-Catapodion balearici de Foucault & Bioret 2010 corr. Tomaselli et al. 2020 alliance (class Saginetea maritimae Westhoff, Van Leeuwen & Adriani 1962, order Saginetalia maritimae Westhoff, Van Leeuwen & Adriani 1962; [58]). This annual spring vegetation is in catenal contact with the perennial communities belonging to the Crithmo-Staticetea class.

Figure 3. Cluster analysis of rocky coast communities. Plant communities: 1. Limonietum syracusani; 2. Limonio-Arthrocnemetum macrostachyi; 3. Lotus cytisoides and Frankenia hirsuta comm.; 4. Parapholido incurvae-Spergularietum marinae ass. Nova.

Figure 3. Cluster analysis of rocky coast communities. Plant communities: 1. Limonietum syracusani; 2. Limonio-Arthrocnemetum macrostachyi; 3. Lotus cytisoides and Frankenia hirsuta comm.; 4. Parapholido incurvae-Spergularietum marinae ass. Nova.

Table 1. Parapholido incurvae-Spergularietum marinae ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1	2*	3	4	5	6	7	8	9	10	11
Original relevé number	17	18	19	20	21	22	23	24	25	26	27
Numbers Cluster	4	4	4	4	4	4	4	4	4	4	4
Surface (mq)	2	2	3	3	2	2	2	2	2	2	2
Coverage(%)	60	70	80	60	100	80	70	85	85	85	85
Altitude (m a.s.l.)	2	3	2	3	2	2	8	6	6	6	6
Floristic richness	6	8	10	4	11	14	4	7	6	7	7	presence
Char. Ass.
Parapholis incurva (L.) C.E. Hubb.	2	2	3	3	3	2	2	4	3	4	3	11
Char. Sileno sedoidis-Catapodion balearici de Foucault & Bioret 2010 corr. Tomaselli et al 2020
Catapodium balearicum (Willk.) H. Scholz	+	1	.	.	.	.	.	.	.	.	.	2
Silene sedoides Poir.	.	+	.	.	.	.	.	.	.	.	+	2
Char. Saginetea maritimae Westhoff, Van Leeuwen & Adriani 1962, Saginetalia maritimae Westhoff, Van Leeuwen & Adriani 1962
Spergularia marina (L.) Besser	3	4	+	1	+	3	1	1	+	1	2	11
Beta vulgaris subsp. maritima (L.) Arcang.	+	+	1	.	+	1	.	1	+	1	.	8
Medicago littoralis Rohde ex Loisel.	+	+	+	.	3	1	.	.	.	+	+	7
Plantago coronopus L.	+	1	1	1	.	.	.	.	.	.	.	4
Mesembryanthemum nodiflorum L.	.	.	1	.	.	.	.	+	.	.	.	2
Matthiola tricuspidata (L.) W.T. Aiton	.	.	.	.	.	+	.	.	.	.	.	1
Other species
Lotus cytisoides L.	.	.	+	1	+	.	+	+	1	+	.	7
Frankenia hirsuta L.	.	.	+	.	+	.	2	1	1	+	1	7
Trifolium resupinatum L.	.	1	.	.	+	+	.	+	+	+	+	7
Anthemis arvensis L.	.	.	1	.	1	+	.	.	.	.	.	3
Silene colorata Poir.	.	.	.	.	+	+	.	.	.	.	.	2
Glaucium flavum Crantz	.	.	.	.	+	+	.	.	.	.	.	2
Crithmum maritimum L.	.	.	.	.	.	+	.	.	.	.	.	1
Plantago macrorhiza Poir.	.	.	.	.	.	+	.	.	.	.	.	1
Trifolium nigrescens Viv.	.	.	.	.	.	+	.	.	.	.	.	1
Medicago truncatula Gaertn.	.	.	+	.	.	.	.	.	.	.	.	1
Lotus ornithopodioides L.	.	.	.	.	.	+	.	.	.	.	.	1
Reichardia picroides (L.) Roth	.	.	.	.	+	.	.	.	.	.	.	1
Sonchus asper (L.) Hill	.	.	.	.	.	+	.	.	.	.	.	1
Tamarix africana Poir.	.	.	.	.	.	.	.	.	.	.	+	1

Table 1. Parapholido incurvae-Spergularietum marinae ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1	2*	3	4	5	6	7	8	9	10	11
Original relevé number	17	18	19	20	21	22	23	24	25	26	27
Numbers Cluster	4	4	4	4	4	4	4	4	4	4	4
Surface (mq)	2	2	3	3	2	2	2	2	2	2	2
Coverage(%)	60	70	80	60	100	80	70	85	85	85	85
Altitude (m a.s.l.)	2	3	2	3	2	2	8	6	6	6	6
Floristic richness	6	8	10	4	11	14	4	7	6	7	7	presence
Char. Ass.
Parapholis incurva (L.) C.E. Hubb.	2	2	3	3	3	2	2	4	3	4	3	11
Char. Sileno sedoidis-Catapodion balearici de Foucault & Bioret 2010 corr. Tomaselli et al 2020
Catapodium balearicum (Willk.) H. Scholz	+	1	.	.	.	.	.	.	.	.	.	2
Silene sedoides Poir.	.	+	.	.	.	.	.	.	.	.	+	2
Char. Saginetea maritimae Westhoff, Van Leeuwen & Adriani 1962, Saginetalia maritimae Westhoff, Van Leeuwen & Adriani 1962
Spergularia marina (L.) Besser	3	4	+	1	+	3	1	1	+	1	2	11
Beta vulgaris subsp. maritima (L.) Arcang.	+	+	1	.	+	1	.	1	+	1	.	8
Medicago littoralis Rohde ex Loisel.	+	+	+	.	3	1	.	.	.	+	+	7
Plantago coronopus L.	+	1	1	1	.	.	.	.	.	.	.	4
Mesembryanthemum nodiflorum L.	.	.	1	.	.	.	.	+	.	.	.	2
Matthiola tricuspidata (L.) W.T. Aiton	.	.	.	.	.	+	.	.	.	.	.	1
Other species
Lotus cytisoides L.	.	.	+	1	+	.	+	+	1	+	.	7
Frankenia hirsuta L.	.	.	+	.	+	.	2	1	1	+	1	7
Trifolium resupinatum L.	.	1	.	.	+	+	.	+	+	+	+	7
Anthemis arvensis L.	.	.	1	.	1	+	.	.	.	.	.	3
Silene colorata Poir.	.	.	.	.	+	+	.	.	.	.	.	2
Glaucium flavum Crantz	.	.	.	.	+	+	.	.	.	.	.	2
Crithmum maritimum L.	.	.	.	.	.	+	.	.	.	.	.	1
Plantago macrorhiza Poir.	.	.	.	.	.	+	.	.	.	.	.	1
Trifolium nigrescens Viv.	.	.	.	.	.	+	.	.	.	.	.	1
Medicago truncatula Gaertn.	.	.	+	.	.	.	.	.	.	.	.	1
Lotus ornithopodioides L.	.	.	.	.	.	+	.	.	.	.	.	1
Reichardia picroides (L.) Roth	.	.	.	.	+	.	.	.	.	.	.	1
Sonchus asper (L.) Hill	.	.	.	.	.	+	.	.	.	.	.	1
Tamarix africana Poir.	.	.	.	.	.	.	.	.	.	.	+	1

Figure 4. Photo plate illustrating different habitat types: (A-B) Psammophylous vegetation of the coast dunes (Saline di Priolo); (C-D) Rocky coast vegetation with Limonium syracusanum and Crithmum maritimum. (Penisola di Magnisi), (E) Rocky coast with Artemisia arborescens vegetation mixed with Hyparrhenia hirta dry grassaland; (F) Garrigues with Tymbra capitata (Penisola di Magnisi); (G-H) Subhalophilous ephemeral communities with Spergularia marina e Parapholis incurva (Penisola di Magnisi).

Figure 4. Photo plate illustrating different habitat types: (A-B) Psammophylous vegetation of the coast dunes (Saline di Priolo); (C-D) Rocky coast vegetation with Limonium syracusanum and Crithmum maritimum. (Penisola di Magnisi), (E) Rocky coast with Artemisia arborescens vegetation mixed with Hyparrhenia hirta dry grassaland; (F) Garrigues with Tymbra capitata (Penisola di Magnisi); (G-H) Subhalophilous ephemeral communities with Spergularia marina e Parapholis incurva (Penisola di Magnisi).

6. Coastal Wetlands Vegetation (Figure 5,7)

Helophytic and Herbaceous Perennial Communities of Fresh and Brackish Waters

The wetland areas close to the industrial area, subjected to long periods of submersion, are covered by perennial vegetation dominated by helophytes, referable to the class Phragmito-Magnocaricetea Klika in Klika et Novác 1941. In particular, according to the flooding period and water depth, the following zonation has been observed: in deeper waters (60-80 cm) the Typhetum domingensis Brullo, Minissale & Spamp. 1994; in shallow waters (50-60 cm) the Eleocharido-Alismetum lanceolati Minissale & Spampinato 1987, characterized by the dominance of Eleocharis palustris and Alisma lanceolatum; in correspondence of small ponds in proximity of the sea, with 40-50 cm water depth, drying in summer, with clayey-sandy soils, the Bolboschoeno-Alismetum lanceolati occurs, a new association described here (Rel.6, Tab.2), characterized by the dominance of Alisma lanceolatum and Bolboschoenus maritimus, and which can be referred to the Glycerio-Sparganion neglecti Br.-Bl. & Sissing in Boer 1942 (Nasturtio-Glycerietalia fluitantis Pignatti 1953). The edges of the “Saline di Priolo” are covered by monophytic vegetation dominated by Phragmites australis, belonging to the Phragmitetum communis (Gams, 1927) Schmale 1939. This latter association is widespread in Sicily along both the coastal strip, the middle and final stretch of watercourses, where there is stagnant water with a certain degree of eutrophication. Often, when favoured by waters rich in nitrates, it replaces the natural halophilic vegetation of the Salicornietea fruticosae class [8, 18].

Figure 5. Cluster analysis of coastal wetlands vegetation. Plant communities: 1. Junco subulati-Sarcocornietum alpini/Arthrocaulo meridionalis-Juncetum subulati/Suaedo-Salicornietum patulae; 2. Lythro hyssopifoliae-Crassuletum vaillantii; 3. Agropyro scirpei-Inuletum crithmoidis/ Halimiono-Suaedetum verae; 4. Phragmition/ Scirpion compacti/Glycerio-sparganion; 5. Euphorbio hirsutae-Lotetum preslii/Juncus acutus comm.; 6. Limbardo crithmoidis-Tamaricetum africanae.

Figure 5. Cluster analysis of coastal wetlands vegetation. Plant communities: 1. Junco subulati-Sarcocornietum alpini/Arthrocaulo meridionalis-Juncetum subulati/Suaedo-Salicornietum patulae; 2. Lythro hyssopifoliae-Crassuletum vaillantii; 3. Agropyro scirpei-Inuletum crithmoidis/ Halimiono-Suaedetum verae; 4. Phragmition/ Scirpion compacti/Glycerio-sparganion; 5. Euphorbio hirsutae-Lotetum preslii/Juncus acutus comm.; 6. Limbardo crithmoidis-Tamaricetum africanae.

Table 2. Bolboschoeno-Alismetum lanceolati ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1		2	3	4	5	6*	7	8
Original relevé number	22		23	24	26	27	30	31	32
Numbers Cluster	4		4	4	4	4	4	4	4
Surface (mq)	16		16	16	16	16	16	16	16
Coverage(%)	80		75	85	90	100	90	90	90
Altitude (m a.s.l.)	5		5	5	5	3	2	2	2
Floristic richness	8		17	11	9	10	12	11	7	presence
Char. Ass.
Bolboschoenus maritimus (L.) Palla	4		1	2	1	4	2	4	2	8
	Char. Glycerio-Sparganion neglecti Br.-Bl. & Sissing in Boer 1942
Alisma lanceolatum With.	2		4	4	4	3	4	4	4	8
	Char. Phragmito-Magnocaricetea Klika in Klika & Novák 1941
Phragmites australis (Cav.) Trin. ex Steud.	+		.	.	1	.	+	1	1	5
Veronica anagallis-aquatica L.	+		1	+	.	.	+	.	+	5
Eleocharis palustris (L.) Roem. & Schult.	.		+	.	.	1	1	.	.	3
Typha domingensis (Pers.) Steud.	.		.	.	.	.	.	1	1	2
Carex otrubae Podp.	.		+	.	.	.	.	.	.	1
Transgr. Molinio-Arrhenatheretea R.Tx.1937
Potentilla reptans L.	.		+	+	+	+	1	+	.	6
Lotus corniculatus L. subsp. preslii (Ten.) P.Fourn.	.		1	+	+	.	1	1	.	5
Lythrum junceum Banks & Sol.	+		1	1	+	.	.	.	.	4
Phyla nodiflora (L.) Greene	.		.	.	.	.	2	1	1	3
Juncus articulatus L.	.		.	.	.	.	2	+	1	3
Trifolium fragiferum L.	.		+	+	.	.	.	.	.	2
Other species										8
Symphyotrichum squamatum (Spreng.) G.L. Nesom	.		+	+	+	+	+	+	.	6
Mentha pulegium L.	+		1	+	+	+	.	.	.	5
Ranunculus trilobus Desf.	.		+	1	+	+	.	.	.	4
Tamarix africana Poir.	1		.	.	.	1	.	1	.	3
Plantago media L.	.		+	.	.	.	+	+	.	3
Holcus lanatus L.	.		1	+	.	.	.	.	.	2
Juncus hybridus Brot.	.		+	.	.	.	.	.	.	1
Isolepis cernua (Vahl) Roem. & Schult.	.		.	.	.	.	+	.	.	1
Juncus acutus L.	.		.	.	.	+	.	.	.	1
Carex extensa Gooden.	.		+	.	.	.	.	.	.	1
Vitex agnus-castus L.	.		.	.	.	+	.	.	.	1
Rumex pulcher L.	.		+	.	.	.	.	.	.	1
Chara sp.	1		.	.	.	.	.	.	.	1

Table 2. Bolboschoeno-Alismetum lanceolati ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1		2	3	4	5	6*	7	8
Original relevé number	22		23	24	26	27	30	31	32
Numbers Cluster	4		4	4	4	4	4	4	4
Surface (mq)	16		16	16	16	16	16	16	16
Coverage(%)	80		75	85	90	100	90	90	90
Altitude (m a.s.l.)	5		5	5	5	3	2	2	2
Floristic richness	8		17	11	9	10	12	11	7	presence
Char. Ass.
Bolboschoenus maritimus (L.) Palla	4		1	2	1	4	2	4	2	8
	Char. Glycerio-Sparganion neglecti Br.-Bl. & Sissing in Boer 1942
Alisma lanceolatum With.	2		4	4	4	3	4	4	4	8
	Char. Phragmito-Magnocaricetea Klika in Klika & Novák 1941
Phragmites australis (Cav.) Trin. ex Steud.	+		.	.	1	.	+	1	1	5
Veronica anagallis-aquatica L.	+		1	+	.	.	+	.	+	5
Eleocharis palustris (L.) Roem. & Schult.	.		+	.	.	1	1	.	.	3
Typha domingensis (Pers.) Steud.	.		.	.	.	.	.	1	1	2
Carex otrubae Podp.	.		+	.	.	.	.	.	.	1
Transgr. Molinio-Arrhenatheretea R.Tx.1937
Potentilla reptans L.	.		+	+	+	+	1	+	.	6
Lotus corniculatus L. subsp. preslii (Ten.) P.Fourn.	.		1	+	+	.	1	1	.	5
Lythrum junceum Banks & Sol.	+		1	1	+	.	.	.	.	4
Phyla nodiflora (L.) Greene	.		.	.	.	.	2	1	1	3
Juncus articulatus L.	.		.	.	.	.	2	+	1	3
Trifolium fragiferum L.	.		+	+	.	.	.	.	.	2
Other species										8
Symphyotrichum squamatum (Spreng.) G.L. Nesom	.		+	+	+	+	+	+	.	6
Mentha pulegium L.	+		1	+	+	+	.	.	.	5
Ranunculus trilobus Desf.	.		+	1	+	+	.	.	.	4
Tamarix africana Poir.	1		.	.	.	1	.	1	.	3
Plantago media L.	.		+	.	.	.	+	+	.	3
Holcus lanatus L.	.		1	+	.	.	.	.	.	2
Juncus hybridus Brot.	.		+	.	.	.	.	.	.	1
Isolepis cernua (Vahl) Roem. & Schult.	.		.	.	.	.	+	.	.	1
Juncus acutus L.	.		.	.	.	+	.	.	.	1
Carex extensa Gooden.	.		+	.	.	.	.	.	.	1
Vitex agnus-castus L.	.		.	.	.	+	.	.	.	1
Rumex pulcher L.	.		+	.	.	.	.	.	.	1
Chara sp.	1		.	.	.	.	.	.	.	1

The edges of depressed areas, with clayey-sandy soils periodically flooded, develop a perennial herbaceous vegetation enriched by floristic elements typical of the Molinio-Arrhenatheretea Tx. 1937, such as Lythrum junceum, Potentilla reptans, Juncus articulatus, Oenanthe globosa, Trifolium fragiferum, Euphorbia hirsuta, Teucrium scordium, Kickxia commutata, Phyla nodiflora, etc. Due to its ecological and floristic features, a new association with the name Euphorbio hirsutae-Lotetum preslii is here described (Rel.2, Tab.3), characterized by the dominance of Lotus corniculatus subsp. preslii and Euphorbia hirta, which is referred to the Paspalo-Agrostion semiverticillati Br.-Bl. in Br.-Bl. Roussine & Negre 1952 (Paspalo-Heleochloetalia Br.-Bl. ex Rivas Goday 1956).

Table 3. Euphorbio hirsutae-Lotetum preslii ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1	2*
Original relevé number	40	41
Numbers Cluster	5	5
Surface (mq)	16	16
Coverage(%)	100	90
Altitude (m a.s.l.)	2	6
Floristic richness	18	20	presence
Char. Ass.
Lotus corniculatus L. subsp. preslii (Ten.) P.Fourn.	3	3	2
Euphorbia hirsuta L.	2	2	2
Char. Paspalo-Agrostion semiverticillati Br.-Bl. in Br.-Bl. Roussine & Negre 1952 and Paspalo-Heleochloetalia Br.-Bl. ex Rivas Goday 1956
Symphyotrichum squamatum (Spreng.) G. L. Nesom	1	+	2
Char. Molinio-Arrhenatheretea R.Tx.1937
Phyla nodiflora (L.) Greene	1	3	2
Lythrum junceum Banks & Sol.	3	1	2
Potentilla reptans L.	+	2	2
Juncus articulatus L.	1	+	2
Scirpoides holoschoenus (L.) Soják	1	+	2
Teucrium scordium L.	+	+	2
Oenanthe globulosa L.	.	+	1
Kickxia commutata (Bernh. ex Rchb.) Fritsch	.	1	1
Trifolium resupinatum L.	+	.	1
Other species
Bolboschoenus maritimus (L.) Palla	+	+	2
Dipsacus fullonum L.	+	.	1
Rubus ulmifolius Schott	1	.	1
Tamarix africana Poir.	1	.	1
Schenkia spicata (L.) G. Mans.	.	2	1
Cynodon dactylon (L.) Pers.	.	2	1
Daucus carota L. subsp. maritimus (Lam.) Batt.	+	.	1
Xanthium italicum Moretti	.	1	1
Ranunculus trilobus Desf.	1	.	1
Mentha pulegium L.	.	1	1
Plantago media L.	.	1	1
Carex extensa Gooden.	1	.	1
Juncus acutus L.	2	.	1
Phragmites australis (Cav.) Trin. ex Steud.	.	+	1
Alisma lanceolatum With.	.	+	1
Typha domingensis (Pers.) Steud.	.	+	1

Table 3. Euphorbio hirsutae-Lotetum preslii ass. nova hoc loco–Sampling plots main features of plant community investigated.

Relevé number	1	2*
Original relevé number	40	41
Numbers Cluster	5	5
Surface (mq)	16	16
Coverage(%)	100	90
Altitude (m a.s.l.)	2	6
Floristic richness	18	20	presence
Char. Ass.
Lotus corniculatus L. subsp. preslii (Ten.) P.Fourn.	3	3	2
Euphorbia hirsuta L.	2	2	2
Char. Paspalo-Agrostion semiverticillati Br.-Bl. in Br.-Bl. Roussine & Negre 1952 and Paspalo-Heleochloetalia Br.-Bl. ex Rivas Goday 1956
Symphyotrichum squamatum (Spreng.) G. L. Nesom	1	+	2
Char. Molinio-Arrhenatheretea R.Tx.1937
Phyla nodiflora (L.) Greene	1	3	2
Lythrum junceum Banks & Sol.	3	1	2
Potentilla reptans L.	+	2	2
Juncus articulatus L.	1	+	2
Scirpoides holoschoenus (L.) Soják	1	+	2
Teucrium scordium L.	+	+	2
Oenanthe globulosa L.	.	+	1
Kickxia commutata (Bernh. ex Rchb.) Fritsch	.	1	1
Trifolium resupinatum L.	+	.	1
Other species
Bolboschoenus maritimus (L.) Palla	+	+	2
Dipsacus fullonum L.	+	.	1
Rubus ulmifolius Schott	1	.	1
Tamarix africana Poir.	1	.	1
Schenkia spicata (L.) G. Mans.	.	2	1
Cynodon dactylon (L.) Pers.	.	2	1
Daucus carota L. subsp. maritimus (Lam.) Batt.	+	.	1
Xanthium italicum Moretti	.	1	1
Ranunculus trilobus Desf.	1	.	1
Mentha pulegium L.	.	1	1
Plantago media L.	.	1	1
Carex extensa Gooden.	1	.	1
Juncus acutus L.	2	.	1
Phragmites australis (Cav.) Trin. ex Steud.	.	+	1
Alisma lanceolatum With.	.	+	1
Typha domingensis (Pers.) Steud.	.	+	1

The large wetland area of the “Saline di Priolo”, permanently flooded by more or less deep salt and brackish waters, is characterized by the hydrophytic submerged communities of Enteromorpho intestinalidis-Ruppietum maritimae Westhoff ex R.Tx. & Böckelmann 1957; this vegetation is characterized by the dominance of Ruppia maritima, which occasionally grows with green algae as Enteromorpha intestinalis. In the study area these communities are quite frequent, favoured by waters rich in nitrates from the surrounding agricultural fields, and are ussually in catenal contact with the bank vegetation generally represented by annual halophilous communities of the Thero-Suaedetea Rivas-Martínez 1972 (habitat 1310 "Annual pioneer vegetation in Salicornia and other species of muddy and sandy areas") and by perennial halophilous communities of Salicornietea fruticosae Br.-Bl. & Tx. ex A. Bolòs y Vayreda & O. de Bolòs 1950 (habitat 1420 "Mediterranean and thermo-Atlantic grasslands and fruit groves (Sarcocornetea fruticosi)”). These last communities are characterized by the presence of perennial Amaranthaceae species, and differ in species composition and cover in relation to the flooding period, thus characterizing a typical zonation from the innermost to the outer part of the brackish basin. Usually, in the inner part area of the salt marsh, subjected to long periods of submersion, the Junco subulati-Sarcocornietum alpini Brullo & Sciandrello in Giusso Del Galdo et al. [15], and the Arthrocaulo meridionalis-Juncetum subulati Brullo & Furnari 1976 nom. corr. Sciandrello et al. 2019 are found; in the more peripheral part of the saltmarsh, rarely subjected to submersion, the Agropyro scirpei-Inuletum crithmoidis Brullo in Brullo et al. 1988 and the Halimiono-Suaedetum verae Molinier et Tallon 1970 corr. Géhu 1984 communities occur. These latter, are halo-nitrophilic communities that, at present, have a very scattered distribution in the study area. The innermost parts of the salt marshes, drying up in the summer-autumn period, are interested by succulent annual species of Amarantaceae with summer cycle, such as Salicornia perennans (= Salicornia patula) and Suaeda maritima, ascribable to the Suaedo-Salicornietum patulae Brullo & Furnari ex Géhu et Géhu-Franck 1984 association. This vegetation is typical of salty soils rich in organic matter. Usually, it alternates with Ruppia maritima communities over the growing season, with Ruppietum maritimae hydrophytic communities growing during the flooding period, and the Suaedo-Salicornietum patulae in summer/autumn, on the dried up substrata. On soils rich in sandy-silty components and subjected to short periods of submersion it is significant the presence of Juncus acutus communities. This pythocoenosis comprises hygro-halophilous hemicryptophytes and geophytes, such as Scirpoides holoschoenus, Juncus subulatus, Carex extensa, which allow us to refer it, despite the absence of Juncus maritimus, to the Juncetum maritimo-acuti Horvatic 1934. Small marginal areas rarely subject to flooding, on sandy soils, are covered by an herbaceous dense vegetation dominated by Elytrygia atherica, species that forms dense and paucispecific populations. In correspondence of depressed areas characterized by a periodic supply of sandy-silty material, a sub-halophilous arboreal vegetation characterized by Tamarix africana and T. gallica develops. In some stretches this woody vegetation is enriched with halophilous species typical of the class Salicornietea fruticosae. In particular, the presence of Limbarda crithmoides allows us to ascribe this phytocoenosis to the Inulo crithmoidis-Tamaricetum africanae Gamisans 1992. This association included in the Tamaricion africanae Br.-Bl. et O.Bolòs 1958, alliance of the Nerio-Tamaricetea Br.-Bl. et O.Bolòs 1958, has already been reported for the saltmarshes of south-eastern Sicily [8]. Moreover, in the “Saline di Priolo”, close to the industrial area, grows a patch of woody vegetation dominated by Ulmus minor, probably of anthropogenic origin, in contact with Juncus acutus community.

Temporary Ponds

On the carbonatic substrata of the Magnisi peninsula, in correspondence of small carbonate rocky pools with silty soil periodically flooded, this amphibious ephemeral vegetation occurs during the winter-spring period. From a phytosociological point of view this vegetation type falls within the Isoëto-Nanojuncetea class, referable to habitat 3170* “Mediterranean temporary ponds” habitat. The pools with shallow waters and thin soil, subjected to early drying in spring, are covered by amphibious vegetation dominated by Bulliarda vaillantii and Lythrum hyssopifolia and referrable to the Lythro hyssopifoliae-Crassuletum vaillantii association. In the nearby area of “Capo Murro di Porco”, the association Pulicario grecae-Damasonietum bourgaei Minissale, Santo & Sciandrello 2011 has been described [61], which is very similar to the Lythro hyssopifoliae-Crassuletum vaillantii community detected in the Magnisi peninsula due to the presence of Damasonium bourgaei.

7. Dry Grasslands and Garrigues/Shrubs (Figure 6,7)

The degradation of the Mediterranean maquis with Pistacia lentiscus allows the expansion of garrigues with Tymbra capitata or grassland dominated by Hyparrhenia hirta (habitat 6220 “Pseudo-steppe with grasses and annuals of the Thero-Brachypodietea”). From a phytosociological point of view, the grassland is very rich in thermo-xerophilous floristic elements typical of the Hyparrhenion hirtae Br.-Bl., P. Silva & Rozeira 1956 alliance, such as Hyparrenia hirta, Andropogon distachyos, Asphodelus ramosus, Ferula communis, Lathyrus clymenum, Thapsia garganica, Foeniculum vulgare subsp. piperitum, Carlina corymbosa, Daucus carota, Eryngium campestre, Moraea sisyrinchium, Lobularia maritima, etc. The habitat includes arid Mediterranean grasslands, typical of shallow oligotrophic soils, characterized by a high number of hemicryptophyte species, generally mixed with annual herbaceous species. This environment is also occupied by therophytic spring vegetation, linked to small layers of soil placed on rocky ledges or in small corrosion pools, and usually forming mosaic with the perennial herbaceous vegetation or garrigues. It is dominated by the presence of some annual Crassulaceae, such as Sedum caeruleum, S. stellatum, Crassula tillaea, etc. This plant community is referable to the Thero-Sedetum caerulei Brullo 1975 association, a pioneer coenosis in contact with garrigue vegetation dominated by Tymbra capitata. On the Magnisi peninsula, the Tymbra capitata vegetation occupies small and limited areas, on carbonate rocky outcrops, due to the frequent summer fires which hinder the evolutionary process of these chamaephytic communities towards the evergreen Mediterranean shrub. For these reasons, there are few diagnostic species of Cisto-Micormerietea, such as Micromeria graeca subsp. tenuifolia, Poterium spinosum and Phagnalon saxatile. The rocky slopes facing west of the Magnisi peninsula are home to communities dominated by Artemisia arborescens that, for their ecological, structural, and floristic features, can be referred to the Atriplici halimi-Artemisietum arborescentis association [62], despite the lack of the characteristic species Atriplex halimus. This vegetation is in contact towards the coast with the halophilous coastal vegetation of the Crithmo-Limonieta, while landwards with the Hyparrhenia steppe grasslands. It can be considered as a permanent edaphic halo-nitrophilous community whose evolution is prevented by anthropic disturbance, combined with the action of coastal winds. Similar communities have been found in the Lachea island, near Catania [63]. Furthermore, the peninsula is affected by extensive annual meadows dominated by Stipellula capensis mainly favored by summer fires and by perennial herbaceous formations dominated by Oloptum miliaceum linked to grazing.

Figure 6. Cluster analysis of dry grasslands, garrigues and shrubs. Plant communities: 1. Artemisia arborescens comm./Hyparrhenietum hirto-pubescentis/ Thymbra capitata comm.; 2. Thero-Sedetum caerulei; 3. Oloptum miliaceum comm.; 4. Stipellula capensis comm.

Figure 6. Cluster analysis of dry grasslands, garrigues and shrubs. Plant communities: 1. Artemisia arborescens comm./Hyparrhenietum hirto-pubescentis/ Thymbra capitata comm.; 2. Thero-Sedetum caerulei; 3. Oloptum miliaceum comm.; 4. Stipellula capensis comm.

Figure 7. Photo plate illustrating different habitat types: (A) Saline di Priolo during the summer (B) Juncus acutus community (Saline di Priolo); (C) Phragmites australis community in contact with wetlands of Saline di Priolo, (D) Tamarix sp pl. vegetation, (E) Bolboschoeno-Alismetum lanceolati ass. nova (Saline di Priolo); (F) Suaedo-Salicornietum patulae (Saline di Priolo); (G) Euphorbio hirsutae-Lotetum preslii ass. nova (Saline di Priolo); (H) Elymetum atherici (Saline di Priolo).

Figure 7. Photo plate illustrating different habitat types: (A) Saline di Priolo during the summer (B) Juncus acutus community (Saline di Priolo); (C) Phragmites australis community in contact with wetlands of Saline di Priolo, (D) Tamarix sp pl. vegetation, (E) Bolboschoeno-Alismetum lanceolati ass. nova (Saline di Priolo); (F) Suaedo-Salicornietum patulae (Saline di Priolo); (G) Euphorbio hirsutae-Lotetum preslii ass. nova (Saline di Priolo); (H) Elymetum atherici (Saline di Priolo).

Diacronic Analysis – Landscape Composition and Configuration

The photointerpretation of the oldest aerial photos (1955) allowed the identification of 10 main types of plant communities, that is a limited number of classes if compared to the number of types (19) derived from the photointerpretation of the recent aerial photos (2015) (Figures 8,9). This discrepancy is partly due to a greater spatial and thematic resolution of the aerial images and then of the map in 2015, but also to the presence of artificial, synanthropic and semi-natural classes which were not present in 1955, the landscape being completely natural at that time. In fact, the comparison of the two periods highlights that the anthropogenic transformations and the almost complete occupation of the coastal environments by industrial settlements have caused the sharp reduction of the dune and wetland systems, due to the leveling and removal of sand and to the reclamation activities (Tab. 5). In particular, the results show a reduction of the aquatic vegetation (Ruppion maritimae) of the Saline di Priolo which decreased from 85 ha (22,6%) in 1955 to only 26 ha (7,4%) in 2015, and the disappearance of the Priolo salt-works, an ancient system for the production of sea salt from sea water, which once occupied an area of 5 hectares. As well known, salt-works and salt pans are anthropic modifications of coastal lagoons and, although of anthropic origin, they maintain some of the floristic and faunal peculiarities of the natural systems. The saltmarsh communities (Juncetea maritimi, Salicornietea fruticosae), in catenal contact with aquatic vegetation, have also undergone a strong reduction from 93 ha (37%) in 1955 to only 25 ha (8%) in 2015. The annual habitats of the costaline (Euphorbion peplidis/Maresion nanae) and perennial dune habitat characterized by Elytrigia juncea (Elytrigienion junceae) suffered a reduction from 40 ha (11%) to 12 ha (3,5 %). The industrial transformation of the area has been a very important driver of changes affecting the coastal environments, mainly because of the massive installation covering a surface of 87 ha (25%); it is the widest land-use typology of the studied area together with reforestation 44 ha (12,6%) and uncultivated/abandoned lands colonized by pioneer grassland vegetation (Echio-Galactition) with a surface of 96 ha (27%). A surprising data concerns the current extension of the woodland cover (about 7 ha), in the Saline di Priolo, of Tamarix sp. pl. vegetation, which in the past was not present, probably due to the high salt concentrations in the soil linked to the activities of salt extraction (salt-works).

Figure 8. Current vegetation map (2015).

Figure 8. Current vegetation map (2015).

Figure 9. Historical vegetation map (1955).

Figure 9. Historical vegetation map (1955).

Table 5. Surfaces comparison from the historical stereophoto (1955) and current aerial photos (2015).

	1955	%	2023	%
Driftline (Euphorbion peplidis)	29	7,8	8	2,3
Shifting dunes (Elytrigienion junceae)	11	2,8	4	1,2
Saline	19	5,2	0	0,0
Aquatic vegetation (Ruppion maritimae)	85	22,6	25,9	7,4
Salt marshes vegetation (Salicornietea fruticosae)	53	14,1	2,2	0,6
Hygrophylous vegetation with Juncus acutus (Juncetea maritimi)	40	10,6	23	6,5
Phragmites australis vegetation (Phragmito-Magnocaricetea)	0	0,0	5,89	1,7
Woods with Tamarix sp. pl. (Nerio-Tamaricetea)	0	0,0	6,6	1,9
Woods with Ulmus minor (Populion albae)	0	0,0	0,557	0,2
Rocky coast vegetation (Crithmo-Limonietea)	28	7,4	11,35	3,2
Garrigue with Thymbra capitata (Cisto-Micromerietea)	16,13	4,3	14,31	4,1
Maquis with Ziziphus lotus (Oleo-Ceratonion)	0	0,0	0,87	0,2
Shrub with Artemisia arborescens (Artemision arborescentis)	0	0,0	0,117	0,0
Temporary ponds with Damasonium bourgaei (Isoeto-Nanojuncetea)	0	0,0	0,315	0,1
Hyparrhenia hirta dry grassland (Lygeo-Stipetea)	0	0,0	12,6	3,6
Uncultivated lands (Echio-Galactition)	67	17,8	96	27,3
Rubus ulmifolius vegetation (Pruno-Rubion)	0	0,0	3	0,8
Cultivated lands	28,15	7,5	6	1,7
Reforestation	0	0,0	44,4	12,6
Man-made infrastructure	0	0,0	87	24,7
	376,274		352,261

Table 5. Surfaces comparison from the historical stereophoto (1955) and current aerial photos (2015).

	1955	%	2023	%
Driftline (Euphorbion peplidis)	29	7,8	8	2,3
Shifting dunes (Elytrigienion junceae)	11	2,8	4	1,2
Saline	19	5,2	0	0,0
Aquatic vegetation (Ruppion maritimae)	85	22,6	25,9	7,4
Salt marshes vegetation (Salicornietea fruticosae)	53	14,1	2,2	0,6
Hygrophylous vegetation with Juncus acutus (Juncetea maritimi)	40	10,6	23	6,5
Phragmites australis vegetation (Phragmito-Magnocaricetea)	0	0,0	5,89	1,7
Woods with Tamarix sp. pl. (Nerio-Tamaricetea)	0	0,0	6,6	1,9
Woods with Ulmus minor (Populion albae)	0	0,0	0,557	0,2
Rocky coast vegetation (Crithmo-Limonietea)	28	7,4	11,35	3,2
Garrigue with Thymbra capitata (Cisto-Micromerietea)	16,13	4,3	14,31	4,1
Maquis with Ziziphus lotus (Oleo-Ceratonion)	0	0,0	0,87	0,2
Shrub with Artemisia arborescens (Artemision arborescentis)	0	0,0	0,117	0,0
Temporary ponds with Damasonium bourgaei (Isoeto-Nanojuncetea)	0	0,0	0,315	0,1
Hyparrhenia hirta dry grassland (Lygeo-Stipetea)	0	0,0	12,6	3,6
Uncultivated lands (Echio-Galactition)	67	17,8	96	27,3
Rubus ulmifolius vegetation (Pruno-Rubion)	0	0,0	3	0,8
Cultivated lands	28,15	7,5	6	1,7
Reforestation	0	0,0	44,4	12,6
Man-made infrastructure	0	0,0	87	24,7
	376,274		352,261

Table 6 shows the results of the landscape metrics applied to the two habitat maps. Two habitat types identified in 1955 are not shown in the 2015 map, either because disappeared (2110) or because so reduced that they could not be graphically represented (habitat cover less than minimum mappable area). On the other hand, habitat types 1430, 3140, 5220 and 6220 reported in the 2015 habitat map are not present in the 1955 map by the mere fact that they often cover limited surfaces and do not have a basic cartographic product with sufficient resolution, so it was not possible to identify them. Habitat 9320, detected in 2015, was not present in 1955. For all these reasons, we decided to concentrate our considerations on the habitats strictly relevant to the coastal strip and salt marshes (except 1310), namely 1150, 1210, 1240, 1410, 1420.

The values for CA and NumP are showed (Figure 10, A-B). It is quite evident, as already mentioned above, a strong decrease in surface area for all the habitat types under consideration (particularly dramatic for habitat 1420), together with a high fragmentation (increase in the number of patches, particularly evident in 1240). This result is in accordance with the values of MPS (Figure 10, C), which shows a strong decrease, for all habitat types (but particularly evident in 1210, 1240 and 1420), trend resulting from the sharp reduction and fragmentation process of coastal environments. As well known, Shape index describes the ratio between the perimeter of the patch and the square root of patch area; AWMSI equals the average shape index (SHAPE) of patches of the corresponding patch type, weighted by patch area. In general, values increase as the shapes of patches become more complex [64]. In Figure 10 (D-E), AWMSI values are shown; no major differences are detectable between the two years of observation, which means that, despite the ongoing dynamics, the spatial complexity in individual classes is more or less the same. MPAR is another measure of shape complexity, but because it is not standarised to a certain shape (e.g. a square), it describes the patch complexity in a straightforward way. Also in this case, no particular changes can be evidences between 1955 and 2015, except for habitat 1240, with a sharp increasing in MPAR, probably linked to the fragmentation of the habitat into numerous small patches of irregularly linear shape.

Table 6. Summary table of the landscape metrics applied to the different habitats in the 1955 and 2015 maps; the grey rows refer to those habitat types which was possible to detect cartographically only on one of the two dates and which therefore were not the subject of temporal analysis.

Table 6. Summary table of the landscape metrics applied to the different habitats in the 1955 and 2015 maps; the grey rows refer to those habitat types which was possible to detect cartographically only on one of the two dates and which therefore were not the subject of temporal analysis.

Figure 10. CA (Class Area) and NumP (Number of Patches) (A-B); MPS (Mean Patch Size) (C); AWMSI (Area Weighted Mean Shape Size) and MPAR (Mean Perimeter-Area Ratio) (D-E), of habitat types 1150, 1210, 1240, 1410 and 1420 in 1955 and 2015.

Figure 10. CA (Class Area) and NumP (Number of Patches) (A-B); MPS (Mean Patch Size) (C); AWMSI (Area Weighted Mean Shape Size) and MPAR (Mean Perimeter-Area Ratio) (D-E), of habitat types 1150, 1210, 1240, 1410 and 1420 in 1955 and 2015.

The case study of the Saline di Priolo is a paradigmatic example of how in just a few decades it is possible to destroy entire stretches of coastal environments with negative consequences on the structure and composition of coastal habitats and vascular flora. The comparison of aerial photos over a period of 60 years shows a dramatic change of the natural landscape, with a permanent loss of land in correspondence of the industrial settlements, the almost complete leveling of the dune system and the extensive wetland reclamation (Figure 11). Another similar dramatic example of extensive destruction of coastal environments due to industrial installations has occurred in the Macconi di Gela, along the southern coast of Sicily, with sharp changes in the dune complexes and wetlands [59].

Conservation Status

The floristic-vegetation survey activities and cartographic processing have highlighted 15 habitat types according to the Habitat Directive (Table 7), of which 4 are of priority conservation (1150, 3170, 5220, 6220). Of these15, 5 habitat types turned out to be in Favorable conservation status, 9 in Inadequate conservation status and 3 in Bad conservation status, of the latter one priority conservation habitat (5220* Zyziphus arborescent matorrals) with a decreasing trend. Furthermore, the habitat 2210 “Fixed dunes of the coast (Crucianellion maritimae)”, reported in the Natura 2000 sheet of the “Saline di Priolo” SAC, is to be considered disappeared or previously erroneously reported. Furthermore, the habitats 1410 "Mediterranean salt meadows (Juncetalia maritimi)" and 1420 "Mediterranean and thermo-Atlantic halophilous scrubs (Sarcocornietea fruticosi)", that once covered larger surfaces, are now very reduced and fragmented and result in an Inadequate conservation status. Our results, regarding the dune system, in line with Prisco et al. [65], highlighted the dramatically bad conservation status of dune habitats.

8. Conclusions

The wetland area of the Saline di Priolo and the Magnisi peninsula represent a clear example of a territory profoundly transformed by industrial activities. Added to this is the intense reforestation activity with non-native species that occupy huge areas. These transformations have caused a marked reduction and fragmentation of the coastal habitats and vascular flora. As demonstrated by the diachronic analysis carried out, the area has undergone notable transformations which occurred especially in the 50s and 60s of the last century with the industrialization of the area. Despite that, the wetland system is still able to support specialized flora, vegetation and fauna, and provide meaningful ecosystem services. On the other hand, the abandonment of previously agricultural areas has allowed the recovery of flooded pastures and temporary ponds. It should also be noted that the dune systems, although compromised by the coastal road and bathing establishments, maintains interesting psammophilous communities worth of conservation. Finally, overall the area under study, although strongly modified by intense anthropic activities, still maintains many habitats of great naturalistic interest and areas with high restoration potential.