The Orophilous Shrubby Vegetation of the Juniperetalia hemisphaericae Order in Sicily: A Refuge Habitat for Many Endemic Vascular Species

An in-depth analysis of the orophilous vegetation dominated by Juniperus hemisphaerica in Sicily, based on literature data and unpublished relevés, is presented. A total of 156 phytosociological relevés were processed and analyzed using classification and ordination methods. Overall, 151 vascular plant species were recorded, of which 38% were endemic species, with a dominant hemicryptophytic biological form (49%). Classification of the relevés, supported by ordination, showed two main vegetation groups: one including the Juniperus communities of Mt. Madonie (Cerastio tomentosi–Juniperetum hemisphaericae and Pruno cupanianae–Juniperetum hemisphaericae), and the other including the vegetation of Mt. Etna (Bellardiochloo aetnensis–Juniperetum hemisphaericae and Roso siculae–Juniperetum hemisphaericae ass. nova). Furthermore, a new alliance, Berberido aetnensis–Juniperion hemisphericae, is proposed for Sicily.

The aim of this paper is to provide an updated syntaxonomical classification (at the level of associations and alliances) of the orophilous vegetation dominated by Juniperus hemisphaerica in Sicily, taking into account, for each plant community, the diagnostic species, floristic composition, structure, distribution, and ecological features.In addition, an updated inventory of the endemic flora occurring in the juniper scrub on the high mountains of Sicily is provided, with the hope that this should be a starting point for further research and conservation projects on flora threatened by climate change.

Vegetation Analysis
Classification of the relevés, supported by ordination, showed two main vegetation groups (Figure 1): the first one included the Juniperus communities of Mt.Etna (cluster A) and the other the vegetation of Mt.Madonie (cluster B).On the Etna volcano, three communities were identified, with different ecological and dynamic features: the first, Bellardiochloo aetnensis-Juniperetum hemisphaericae (cluster A2), represents a secondary serial community of the Junipero hemisphaericae-Pinetum calabricae; the second community, described as a new association Roso siculae-Juniperetum hemisphaericae (cluster A1), represents a serial primary edapho-xerophilous vegetation of high mountains (permaseries) [18]; the last community, Junipero hemisphaericae-Pinetum calabricae (cluster A3), represents the forest Plants 2024, 13, 423 3 of 20 vegetation (edaphoxerophilous series) growing on more mature volcanic soils with rocky outcrops, within the supra-Mediterranean belt.The scrub vegetation of Madonie refers to Cerastio tomentosi-Juniperetum hemisphaericae including Junipero hemisphaericae-Abietetum nebrodensis (cluster B4), which represent the first serial community of Junipero hemisphaericae-Abietetum nebrodensis, and Pruno cupanianae-Juniperetum hemisphaericae, including Lino punctati-Seslieretum siculae subass.juniperetosum (cluster B5), a serial community of mesophilous holm oak woods of Acero-Quercetum ilicis.The DCA (Figure 2) shows a clear split into two groups, mainly linked to the different nature of the substrates in the two mountain massifs: carbonatic on Mt.Madonie and volcanic on Mt.Etna.This difference in substrates and age also corresponds to a different floristic richness between the two mountains, clearly higher in the ancient carbonate substrates of Madonie.On the positive side of axis 1 of the diagram are shown the plant communities of Mt.Madonie, with a marginal overlap between the Cerastio tomentosi-Juniperetum hemisphaericae and Pruno cupanianae-Juniperetum hemisphaerica, as shown in the cluster analysis, while on the negative side of axis 1 are distributed the communities of Mt.Etna, with a clear separation, in relation to the altitudinal range, between Bellardiochloo aetnensis-Juniperetum hemisphaericae and Roso siculae-Juniperetum hemisphaericae.On the negative section of axis 1, we also find the Junipero hemisphaericae-Pinetum calabricae, which differs from the shrub Juniperus communities due to its structure and floristic composition.All this confirms that this latest new association differs floristically for some rosaceae (Rosa sp pl.) characterizing the structure of this new community, above all due to its serial primary edapho-xerophilous role of high mountains (1900-2300 m a.s.l.).
Dynamic contacts: In the more evolved substrates it tends towards the orophilous pine forests Junipero hemisphaericae-Pinetum calabricae.
Dynamic contacts: Relict primary orophilous scrub vegetation.Catenal contacts: Generally, at lower altitudes, this association comes in contact with the mesophilous woods of Epipactito-Fagetum sylvaticae (between 1500 m and 2000 m s.l.m.) or, in more xeric conditions, with pine woods, whereas at higher altitudes it is in contact and interspersed with Astragaletum siculi (Frei 1940) Gilli 1943 [14].For these reasons, we propose a new alliance be included in the Juniperetalia hemisphaericae order, which better characterizes the Juniperus communities of high mountains in Sicily from a chorological and structural point of view.
juniper woods, with a geographical distribution in the Central and Eastern Mediterranean.The same authors describe a new alliance, Berberido aetnensis-Pinion laricionis, which replaces Berberidion aetnensis, name illegitimate (ICPN art.29), described by Brullo et al. [14].For these reasons, we propose a new alliance be included in the Juniperetalia hemisphaericae order, which better characterizes the Juniperus communities of high mountains in Sicily from a chorological and structural point of view.

Distribution and Conservation
The cartographic analysis, performed with Quantum GIS software, shows the Juniperus scrub distribution on Mt.Etna, with 89 polygons and 220 geolocalized points, for a total surface area of 323 ha (Figure 4).According to the reference grid (2 × 2 km), this habitat is currently recorded in 24 cells corresponding to a total surface area of 96 km 2 .The slopes of the volcano most affected by juniper groves are mainly to the north and west, at altitudes between 1900 and 2300 m.The juniper undergrowth of the Pinus laricio (not mapped) extends to lower altitudes, up to 1700-1600 m and, in some cases, even to 1500-1400 m, among the Quercus congesta oak woods, near Mt.Maletto (Etna NW), characterizing the shrubby structure of the forest community with high cover values.In addition, it is possible to find isolated junipers, even among the oak woods of Quercis ilex, near Monte Tre Frati (Etna W), and among the oak woods of Quercus cerris, near C.da Giarrita (Etna E).Etna, due to its high altitudes, is the only one of the Sicilian mountain systems to host the relict primary orophilous vegetation dominated by Juniperus hemisphaerica, between 1900 and 2300 m a.s.l., in contact (top) with the vegetation of Astragalus siculus, which rises to almost 2500 m, and (below) with beech woods (between 1800 and 2000 m).On Etna, the Juniperus hemisphaerica vegetation plays two different ecological and dynamic roles: at low altitudes, it occupies the acidophilic climatic series of the beech (Epipactido-Fageto sylvaticae sigmetum), while at high altitudes it assumes a primary role of permanent edaphoxerophilous vegetation.The best-preserved communities are located above the Timparossa beech forest (M.Nero, Etna N), above Mt.Conca (Piano Provenzano, Etna E), above Mt.Guardinazzi-M.Conca (Etna NW), above Mt.Palestra-Mt.Pecoraro (Etna W), between Mt.Scavo and Mt.Frumento Supino (Etna SW), and Mt.Nero degli Zappini (Etna SW).Making a comparison with the geological map of Branca et al. [22], it can be observed that the Juniperus areas are concentrated over, or near, the oldest emerging volcanic substrates of high altitude.This could mean that the oldest volcanic rocks (110-15 ka) functioned as refuge areas for the wood shrub species of the high-altitude volcanic environment [17].In the Madonie Mountains, juniper is distributed at an altitude range between 1400/1500 and 1900 m a.s.l., mainly occupying the climatophilic series of the beech.On the Madonie, it was not possible to map the Juniperus vegetation due to the small and very fragmented patches [23].The mountains affected by Juniperus hemisphaerica, especially on the very windy slopes facing south and south-west, are Monte Quacella, Monte Scalone, above Vallone Madonna degli Angeli, Monte Cavallo, and Monte San Salvatore.According to the reference grid (2 × 2 km), this habitat is currently recorded in six cells (45 geolocalized points) corresponding to a total surface area of 24 km 2 (Figure 5).Our accurate field surveys allowed us to have a deeper knowledge of the distribution and conservation status of Juniperus hemisphaerica habitat.Based on our current assessments and observations in the field, the habitat is currently recorded in thirty cells (

Materials and Methods
This study followed the Braun-Blanquet phytosociological approach [25].A total of 156 phytosociological relevés × 151 species were collected, of which 52 were from the literature and 104 were unpublished.Based on the total set of phytosociological surveys, after eliminating the sporadic species with a presence lower than 4, a matrix of 156 surveys × 93 species was obtained.The original Braun-Blanquet sampling scale was transformed into the ordinal scale according to Van der Maarel [26], and transformation logx + 1 was applied in order to balance the highest and lowest cover values.All the relevés were analyzed using classification and ordination methods.A multivariate analysis (linkage method: Ward's; distance measure: Euclidean) and detrended correspondence analysis (DCA) were applied [27][28][29].Cluster analysis and ordination of the dataset were performed using PC-ORD 6 software [30].The processed relevés from the literature were classified into the following syntaxa: Cerastio tomentosi-Juniperetum hemisphaericae Pignatti & Nimis [12]; Lino punctati-Seslieretum siculae subass.juniperetosum [13]; Cerastio tomentosi-Juniperetum hemisphaericae Pignatti & Nimis [13]; Bellardiochloa aetnensis-Juniperetum hemisphaericae Brullo & Siracusa [14]; and Pruno cupanianae-Juniperetum hemisphaericae Raimondo, Marino & Schicchi 2010 [15].In addition, due to the high vegetation cover of Juniperus hemisphaerica, we also considered Junipero hemisphaericae-Abietetum nebrodensis Brullo & Giusso [14] and Junipero hemisphaericae-Pinetum calabricae Brullo & Siracusa [14].A synoptic table (Table A2) was created to highlight the floristic composition, floristic richness, and altitude among the communities surveyed.Life form, chorology, and families were analyzed in a total of 151 vascular plant species extrapolated from 156 phytosociological relevés of the high-mountain juniper communities of Sicily.In order to define the altitudinal range and spatial distribution of Juniperus hemisphaerica, a total of 220 geolocated points for Etna and 45 points for Madonie were recorded, using GPS Garmin Montana and Quantum GIS software version 3.6.Taxonomic nomenclature, life form, and chorological classification of the endemics for native species follow Pignatti [31].Syntaxonomic classification follows Mucina et al. [16].Bioclimatic classification follows Pesaresi et al. [32].The names of syntaxa comply with the International Code of Phytosociological Nomenclature (ICPN) [33].

Materials and Methods
This study followed the Braun-Blanquet phytosociological approach [25].A total of 156 phytosociological relevés × 151 species were collected, of which 52 were from the literature and 104 were unpublished.Based on the total set of phytosociological surveys, after eliminating the sporadic species with a presence lower than 4, a matrix of 156 surveys × 93 species was obtained.The original Braun-Blanquet sampling scale was transformed into the ordinal scale according to Van der Maarel [26], and transformation logx + 1 was applied in order to balance the highest and lowest cover values.All the relevés were analyzed using classification and ordination methods.A multivariate analysis (linkage method: Ward's; distance measure: Euclidean) and detrended correspondence analysis (DCA) were applied [27][28][29].Cluster analysis and ordination of the dataset were performed using PC-ORD 6 software [30].The processed relevés from the literature were classified into the following syntaxa: Cerastio tomentosi-Juniperetum hemisphaericae Pignatti & Nimis [12]; Lino punctati-Seslieretum siculae subass.juniperetosum [13]; Cerastio tomentosi-Juniperetum hemisphaericae Pignatti & Nimis [13]; Bellardiochloa aetnensis-Juniperetum hemisphaericae Brullo & Siracusa [14]; and Pruno cupanianae-Juniperetum hemisphaericae Raimondo, Marino & Schicchi 2010 [15].In addition, due to the high vegetation cover of Juniperus hemisphaerica, we also considered Junipero hemisphaericae-Abietetum nebrodensis Brullo & Giusso [14] and Junipero hemisphaericae-Pinetum calabricae Brullo & Siracusa [14].A synoptic table (Table A2) was created to highlight the floristic composition, floristic richness, and altitude among the communities surveyed.Life form, chorology, and families were analyzed in a total of 151 vascular plant species extrapolated from 156 phytosociological relevés of the highmountain juniper communities of Sicily.In order to define the altitudinal range and spatial distribution of Juniperus hemisphaerica, a total of 220 geolocated points for Etna and 45 points for Madonie were recorded, using GPS Garmin Montana and Quantum GIS software version 3.6.Taxonomic nomenclature, life form, and chorological classification of the endemics for native species follow Pignatti [31].Syntaxonomic classification follows Mucina et al. [16].Bioclimatic classification follows Pesaresi et al. [32].The names of syntaxa comply with the International Code of Phytosociological Nomenclature (ICPN) [33].

Conclusions
This paper provides a comprehensive and exhaustive framework for the orophilous shrubby vegetation dominated by Juniperus hemisphaerica in Sicily, highlighting the structure, floristic composition, and dynamism of secondary and primary juniper communities.The results of this paper lead us to include the forests dominated by conifers of Sicily and southern Italy (Junipero hemisphaericae-Abietetum nebrodensis, Junipero hemisphaericae-Pinetum calabricae, Junipero hemisphaericae-Abietetum apenninae) in the alliance Berberido aetnensis-Pinion laricionis and order Berberido creticae-Juniperetalia excelsae.The dry juniper scrubs, due to their structure, floristic composition, and geographical distribution, are to be included in the new alliance Berberido aetnensis-Juniperion hemisphericae, proposed by us in this paper, and in the Juniperetalia hemisphaericae order, which best characterizes the juniper communities of Sicily from a geographical point of view.
The calcicolous supra-Mediterranean dry juniper scrubs (Cerastio tomentosi-Juniperetum hemisphaericae and Pruno cupanianae-Juniperetum hemisphaericae) of Mt.Madonie fall within the serial secondary aspects of Luzulo siculae-Fagetum sylvaticae and Aceri campestri-Qurcetum ilicis, respectively.Simultaneously, the silicicolous supra-oro-Mediterranean dry juniper scrubs (Bellardiochloa aetnensis-Juniperetum hemisphaericae and Roso siculae-Juniperetum hemisphaericae) of Mt.Etna fall into two different aspects: the first community plays a secondary serial role of the Junipero hemisphaericae-Pinetum calabricae, and the second community represents serial primary edapho-xerophilous vegetation of high mountains (permaseries).The endemism occurring in the high-mountain juniper communities is extremely high in both geographical contexts and is between 34% on Mt.Madonie and 43% on Mt.Etna, with a hemicryptophytic dominant biological form in both districts (56% for Etna and 60% for Madonie).The relict orophilous vegetation (permaseries), widespread only on Mt.Etna in an altitude range between 1900 m and 2300 m a.s.l., mainly on the northern and western rocky slopes, represents a habitat of extraordinary naturalistic value, not only due to the presence of several narrow endemic plants but also as an ecological niche for some faunal species, such as the Sicilian rock partridge Alectoris graeca whitakeri (Schiebel, 1834), now in strong decline, spotted several times in high altitude areas, where it finds shelter and food among the juniper scrubs.Moreover, this orophilous shrubby vegetation is very sensitive and vulnerable to climate change.It is also for these reasons that we propose, in this paper, the inclusion of this orophilous vegetation in the habitat 9560* "Endemic forest with Juniperus spp."Annex I of the Habitat Directive.
Mediterranean permanent or secondary dry juniper scrub growing in the high mountains of Sicily (Mt.Etna and Mt.Madonie).The shrubby structure is dominated by Juniperus hemisphaerica C. Presl and Berberis aetnensis C. Presl, together with Rosa sicula Tratt., Rosa heckeliana Tratt., Prunus cupaniana Guss., and Sorbus graeca (Spach) Lodd.ex S. Schauer.They find their optimum in the oro-Mediterranean belt of Mt.Etna, mainly on silicicolous substrata in rocky environments affected by the prolonged permanence of snow.