Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines

Ballelli, Sandro; Tesei, Giulio; Pennesi, Riccardo; Allegrezza, Marina

doi:10.3390/life13122273

Open AccessArticle

Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines

¹

Herbarium Universitatis Camerinensis, School of Biosciences and Veterinary Medicine, University of Camerino, Via Pontoni 5, 62032 Camerino, Italy

²

Department of Agricultural, Food and Environmental Sciences, Marche Polytechnic University, Via Brecce Bianche, 60131 Ancona, Italy

^*

Author to whom correspondence should be addressed.

Life 2023, 13(12), 2273; https://doi.org/10.3390/life13122273

Submission received: 16 October 2023 / Revised: 24 November 2023 / Accepted: 25 November 2023 / Published: 28 November 2023

(This article belongs to the Section Plant Science)

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Abstract

:

We present a floristic–vegetational study on a plant community dominated by Geranium argenteum in the Sibillini Mountains (Central Apennines), at the southern limit of its distribution in the Apennines. It is a rare pioneer community located at an elevation of about 2100 m a.s.l. with northern exposure on the fractured rocky ridges and at the edges of the rocky detrital valleys on lithosol, with a prolonged presence of snowpack and gelifraction processes. The results of the phytosociological analysis allow us to propose the new Festuco italicae-Geranietum argentei association referred to as the Leontopodio nivalis-Elynion myosuroidis alliance (Carici rupestris-Kobresietea bellardii class). The comparison with the Alpine and the Northern Apennines phytocoenoses characterized by Geranium argenteum allows us to provide a new interpretation of the syntaxonomical framework concerning the Geranium argenteum communities within its Alpine–Apennine range in light of the new data presented in this paper. The new Festuco italicae-Geranietum argentei association represents a further contribution to the knowledge of the relict alpine vegetation of the Leontopodio nivalis-Elynion myosuroidis alliance in the Sibillini Mountains and thus in the Central Apennines. Finally, habitat monitoring will be essential for assessing the impacts of climate change on this fragile and narrowly restricted plant community.

Keywords:

Alpine–Apennine range; biogeography; Geranium argenteum; syntaxonomy; vegetation

1. Introduction

Geranium argenteum is a rare Italian subendemic species distributed in the Alps (from Southeast France to Slovenia) [1] and within the Apennines ridges [2] (Figure 1). It is a small perennial herbaceous plant (8–15 cm) with all basal leaves arranged in a rosette and with a long and robust rhizome [2]. Geranium argenteum is a pioneer species that grows in open grasslands in neutral to alkaline conditions at nutrient-poor sites in high mountain environments [3,4], with the highest elevation in Val di Fassa (Dolomites Alps), where the species was found in a dolomitic scree at 2350 m a.s.l. [5]. The species occurs in ridge positions more or less exposed to the winds but also on scree slopes thanks to the long rhizome that can penetrate crevices and debris rock [6]. Geranium argenteum prefers calcareous substrate but is also present on siliceous lithologies in the Northern Apennines [7,8].

The origin and biogeographical history of this species are controversial, partly due to the absence of specific phylogenetic data in the literature. On the one hand, some authors indicate G. argenteum as a tertiary species (Gams 1933; Pignatti and Pignatti 2014; Chiarugi 1937) [5,9,10] with an Alpine–Mediterranean distribution, where the current discontinuity of geographic distribution should be considered a direct consequence of the glacial period that fragmented the primitive range of the species [5]. On the other hand, other authors indicate G. argenteum as a species of Alpine origin that migrated southward during the Quaternary glaciations (e.g., Ansaldi et al., 2008) [7].

In the Northern Apennines, the species has a scattered distribution in a few high-altitude sites [6,7,11], to the extent that it is listed as a protected species at the regional level [12,13]. Regarding the Central Apennines, lg. Ottaviani (in Bertoloni (1847): vol. VII pp. 224–225 [14]) reports the presence of G. argenteum “ex Umbria in montibus delle Fonti prope il Sasso Borghese” in the Sibillini Mountains group (Mt. Argentella). This record has not been confirmed in subsequent floristic studies; thus, for a long time, the Northern Apennines were indicated as the southernmost distribution limit of G. argenteum [2]. Only recently has the species been confirmed for the Central Apennines [15,16]; thus, this area automatically becomes the new southern distribution limit of G. argenteum in the Apennines.

Published literature data on plant communities with or dominated by G. argenteum mainly concern the Eastern Alpine chain (e.g., Surina 2005a; Sutter 1969) [17,18], while the published works on the Apennines exclusively concern the distribution and the size of populations at the regional level (e.g., Ansaldi et al., 2008) [7], except for a recent phytosociological study [19] on Mt. Cimone in the Northern Apennines (Figure 1). However, seven unpublished phytosociological relevés characterized by G. argenteum are reported in a thesis [11] for three Northern Apennines Mountain groups, one of which is from the Apuan Alps. Notably, a single relevé from the Apuan Alps (only one station, in the area of Pania della Croce) was also published in Ferrarini 1967 [6] (rel. n. 64 carried out on 14 September 1963).

From the syntaxonomic point of view, the phytosociological associations containing G. argenteum in their epithet currently recognized and sampled within the native range of the species are reported below with the original references at alliance and class levels: Salici retusae-Geranietum argentei Surina 2005 (Soldanello-Salicion retusae alliance, Thlaspietea rotundifolii class) for the Julian Alps in Slovenia [20,21]; Sesleria sphaerocephala-Geranium argenteum ass. prov. Sutter 1969 (Oxytropido-Elynion alliance; Elyno-Seslerietea class) (Sutter 1969), later reported as Seslerio sphaerocephalae-Geranietum argentei Sutter 1969 for the Dolomites [21,22] and as Seslerio caeruleae-Geranietum argentei Sutter 1969 prov for the Hautes Alpes in France [23]; and Geranio argentei-Caricetum rupestris Tomaselli, Foggi, Carbognani, Gennai, et Petraglia 2019 (Oxytropido-Elynion alliance; Carici rupestris-Kobresietea bellardii class) for the Northern Apennines [19].

The objectives of this research are: (i) the floristic–vegetational and ecological characterization of the communities dominated by G. argenteum in the Sibillini Mountain group (Central Apennines) at the southern limit of distribution of the species; (ii) to provide a new interpretation of the syntaxonomical framework concerning the G. argenteum communities within its Alpine–Apennine range in light of the new data presented in this paper.

2. Materials and Methods

2.1. Study Area

The study area is located on Mount Argentella in the Sibillini Mountain range and lies within the Natura 2000 Special Areas of Conservation (SAC IT5210071 “Monti Sibillini (versante umbro)”), included in the Monti Sibillini National Park. The substrate is exclusively calcareous, belonging to the Umbrian–Marche limestone succession and specifically to the Massive Limestone Formation [24]. The morphology is very rugged, with rocky bumps and ridges, scree, sinkhole systems, rocky detrital valleys, and snow beds (Figure 2).

The bioclimatic classification sensu Rivas-Martínez et al. (2011) [25] indicates a temperate macrobioclimate, oceanic bioclimate, and upper orotemperate thermotype [26]. The vegetation is represented by various types of high-altitude grassland communities depending on the morphology and stability of the substrate (Figure 2) and mainly referable to the following habitats of 92/43/EEC Directive Annex I: 6170 “alpine and subalpine calcareous grasslands” with plant communities belonging to the Apennine alliances Leontopodio nivalis-Elynion myosuroidis, Seslerion apenninae, and Ranunculo pollinensis-Nardion strictae; 8120 “Calcareous and calcshist screes of the montane to alpine levels (Thlaspietea rotundifolii)” with plant communities belonging to the Apennine alliance Linario-Festucion dimorphae; and 8210 “Calcareous rocky slopes with chasmophytic vegetation” with plant communities belonging to the Apennine alliance Saxifragion australis (Asplenietea class).

2.2. Vegetation Study

The study of the vegetation was conducted according to the Braun-Blanquet phytosociological method [27]. Each vascular plant detected in the survey area was associated with an abundance value using the seven-point Braun-Blanquet scale according to the following cover values: with cover <1% (r, very few individuals; +, few individuals) and with cover ≥1% (1: from 1% to 5%; 2: from 5% to 25%; 3: from 25% to 50%; 4: from 50% to 75%; 5: from 75% to 100%). The nomenclature of the species follows Bartolucci et al. (2018) [13] with the exception of Luzula italica, which follows Pignatti et al. (2017–2019) [2]. The phytosociological nomenclature follows the rules of the ICPN [28]. The chorological types refer to Pignatti et al. (2017–2019) [1] and Aeschimann et al. (2004) [2]. The chorological types were grouped as follows: endemic (endemic Italian; endemic Alps; subendemic), Mediterranean (Eurimediterranean; Mediterranean–mountain; amphi-Adriatic), Eurasian (Eurasian; European (center, south, southeast); European Caucasian; paleotemperate; southwest Asiatic–Mediterranean), center-European orophytes (European orophytes (center, west); Eurasian orophytes; east Alpine–Carpatian), south-European orophytes (European orophytes (south, southeast, southwest); Alpine–Pyrenaic), boreal (Eurosiberian; circumboreal; Arctic–Alpine), and cosmopolitan (cosmopolitan; subcosmopolitan).

A total of 106 phytosociological relevés were used for the comparisons with the literature data. Four of these were unpublished and were performed in the study area.

The syntaxonomic nomenclature follows Biondi et al. (2014, 2015) [29,30] for the Festuco-Seslerietea class, Chytrý et al. (2015) [31] for the Carici rupestris-Kobresietea bellardii class, and Mucina et al. (2016) [32] the for the other classes.

The plant collections of the new association are preserved at Herbarium Universitatis Camerinensis, School of Biosciences and Veterinary Medicine, University of Camerino, Via Pontoni 5, 62032 Camerino, Italy.

2.3. Statical Analysis

Braun-Blanquet’s cover-abundance values were transformed according to the van der Maarel scale [33] and then subjected to multivariate analysis through the use of the VEGAN community ecology package [34] for R software version 4.2.3 [35]. In order to assess the degree of similarity between the surveys carried out in the study area and those already published on plant communities in the alpine and subalpine planes of the Central Apennines, a cluster analysis was carried out by applying Ward’s minimum variance method to the stratified similarity matrix calculated using the Bray–Curtis index. To analyze the changes in species composition between the different G. argenteum communities, principal component analysis (PCA) was performed. Furthermore, the “indicspecies” R package [36] was used to perform the indicator species analysis [37], in order to identify the species significantly associated with the different G. argenteum communities.

3. Results and Discussion

3.1. Geranium argenteum Community in the Study Area

Association: Festuco italicae-Geranietum argentei ass. nov. (typus rel. n. 2 of Table 1)

Dominant species: Geranium argenteum

Constant species: Armeria gracilis subsp. gracilis, Carex kitaibeliana, Festuca violacea subsp. italica, Gentianella columnae, Geranium argenteum, Poa molinerii, Plantago atrata, Potentilla crantzii, Ranunculus breyninus, Sabulina verna subsp. verna, Saxifraga adscendens subsp. adscendens, Sedum atratum, Silene acaulis subsp. bryoides.

Diagnostic species: Geranium argenteum (characteristic species), Gentianella columnae (differential species), Potentilla brauneana, (differential species), Festuca violacea subsp. italica (differential species), and Achillea barrelieri (transgressive species).

It is an extremely rare and fragmentary pioneer community dominated by G. argenteum (mean cover 44%) with Festuca violacea subsp. italica and Silene acaulis subsp. bryoides that develops exclusively near the summit sector of Monte Argentella (2201 m a.s.l.) in the northern aspects and at an elevation between 2040 and 2080 m a.s.l. (Figure 2 and Figure 3). It is present on the fractured rocky ridges (Figure 4) and at the edges of the rocky detrital valleys on lithosol, in conditions of prolonged presence of the snowpack and gelifraction processes. Thanks to its long and robust rhizome, G. argenteum creeps into the cracks of the pebbles up to the consolidated soil also associated with Silene acaulis subsp. bryoides.

The elaboration of the phytosociological relevés and the comparison with the plant communities occurring in the alpine and subalpine belts of the Central Apennines, which exhibit floristic similarities with the G. argenteum community in the study area (Table S1), highlight the floristic–vegetational autonomy of the G. argenteum community under investigation, for which the new Festuco italicae-Geranietum argentei association is proposed (Table 1).

Table 1. Festuco italicae-Geranietum argentei ass. nov. (typus rel. n° 2, indicated by asterisk).

No. of Relevés	1	2 *	3	4
Elevation (m a.s.l.)	2080	2076	2036	2040
Aspect	N	N	N	N	p
Slope (°)	40	35	30	35	r
Area (mq)	40	10	50	15	e
Cover total %	70	70	70	30	s.
No. of Species	40	31	44	28
Festuco italicae-Geranietum argentei
Geranium argenteum L.	3	4	4	2	4
Festuca violacea Ser. ex Gaudin subsp. italica Foggi, Gr. Rossi et Signorini	3	2	2	1	4
Gentianella columnae (Ten.) Holub	+	1	1	+	4
Achillea barrelieri (Ten.) Sch. Bip. subsp. barrelieri	+	+	+	.	3
Potentilla brauneana Hoppe	.	+	+	+	3
Leontopodio-Elynion, Oxytropido-Elynetalia, Carici rupestris-Kobresietea bellardii
Silene acaulis (L.) Jacq. subsp. bryoides (Jord.) Nyman	+	2	2	1	4
Carex kitaibeliana Degen ex Bech.	1	1	1	+	4
Sabulina verna (L.) Rchb. subsp. verna	+	+	+	+	4
Potentilla crantzii (Crantz) Beck ex Fritsch subsp. crantzii	+	+	+	+	4
Sedum atratum L.	+	+	+	+	4
Erigeron epiroticus (Vierh.) Halácsy	+	+	+	.	3
Leontopodium nivale (Ten.) Hand.-Mazz.	+	+	.	.	2
Omalotheca diminuta (Braun-Blanq.) Bartolucci et Galasso	.	+	.	+	2
Festuco-Seslerietea
Ranunculus breyninus Crantz	+	+	+	+	4
Euphrasia salisburgensis Funck ex Hoppe	+	+	1	.	3
Edraianthus graminifolius (L.) A. DC. subsp. graminifolius	+	+	+	.	3
Bellidiastrum michelii Cass.	1	+	1	.	3
Draba aizoides L. subsp. aizoides	+	.	+	+	3
Pulsatilla alpina (L.) Delarbre subsp. millefoliata (Bertol.) D.M. Moser	+	.	+	.	2
Sesleria juncifolia Wulfen ex Suffren subsp. juncifolia	+	.	+	.	2
Androsace villosa L. subsp. villosa	.	+	+	.	2
Alchemilla nitida Buser	.	.	+	+	2
Gentiana verna L. subsp. verna	.	.	+	+	2
Aster alpinus L. subsp. alpinus	+	.	.	.	1
Carduus defloratus L. subsp. carlinifolius (Lam.) Ces.	+	.	.	.	1
Pedicularis elegans Ten.	+	.	.	.	1
Paronychia kapela (Hacq.) A. Kern. subsp. kapela	+	.	.	.	1
Trinia dalechampii (Ten.) Janch.	.	+	.	.	1
Nardetea strictae and Juncetea trifidii
Plantago atrata Hoppe subsp. atrata	+	+	+	+	4
Taraxacum apenninum (Ten.) DC.	.	+	+	+	4
Crepis aurea (L.) Cass. subsp. glabrescens (Caruel) Arcang.	.	+	1	+	4
Pilosella lactucella (Wallr.) P.D. Sell et C. West subsp. nana (Scheele) M. Laínz	.	.	+	.	1
Luzula italica Parl.	.	.	.	+	1
Botrychium lunaria (L.) Sw.	.	.	.	+	1
Asplenietea trichomanis
Cystopteris fragilis (L.) Bernh.	+	.	+	+	2
Saxifraga paniculata Mill.	+	.	+	+	2
Campanula tanfanii Podlech	+	.	+	.	2
Asplenium viride Huds.	.	.	+	+	2
Thlaspietea rotundifolii
Saxifraga adscendens L. subsp. adscendens	+	+	+	+	4
Doronicum columnae Ten.	+	.	+	+	2
Galium magellense Ten.	+	.	.	.	1
Robertia taraxacoides (Loisel.) DC.	+	.	.	.	1
Ranunculus brevifolius Ten.	+	.	.	.	1
Leucopoa dimorpha (Guss.) H. Scholz et Foggi	.	.	+	.	1
Arabis alpina L. subsp. caucasica (Willd.) Briq.	.	.	.	+	1
Other species
Armeria gracilis Ten. subsp. gracilis	1	1	+	+	4
Poa molinerii Balb.	1	+	+	1	4
Globularia meridionalis (Podp.) O. Schwarz	+	+	+	.	3
Helictochloa praetutiana (Parl. ex Arcang.) Bartolucci, F. Conti, Peruzzi et Banfi subsp. praetutiana	+	+	+	.	3
Koeleria australis A. Kern	+	+	+	.	3
Thymus praecox Opiz subsp. polytrichus (A. Kern ex Borbás) Jalas	1	+	1	.	3
Oreojuncus monanthos (Jacq.) Záv. Drábk. et Kirschner	+	.	+	.	2
Anthyllis vulneraria L. subsp. nana (Ten.) Tammaro	.	+	+	.	2
Cerastium arvense L. subsp. suffruticosum (L.) Ces.	.	.	+	+	2
Ziziphora granatensis (Boiss. et Reut.) Melnikov subsp. alpina (L.) Bräuchler et Gutermann	1	.	.	.	1
Helianthemum oelandicum (L.) Dum. Cours. subsp. incanum (Willk.) G. López	+	.	.	.	1
Myosotis graui Selvi	.	+	.	.	1
Cynanchica pyrenaica (L.) P. Caputo et Del Guacchio subsp. neglecta (Guss.) P. Caputo et Del Guacchio	.	.	+	.	1
Carlina acaulis subsp. caulescens (Lam.) Schübl. et G. Martens	.	.	+	.	1
Anthyllis montana L. subsp. jacquinii (Rchb. f.) Rohlena	.	.	+	.	1

Dates, localities, and geographical coordinates (WGS84–UTM 33T) of relevès performed in the study area: rel. 1, Mt. Argentella, 356137 m E 4747032 m N; rel. 2, Mt. Argentella, 356136 m E 4747040 m N; rel. 3, Mt. Argentella, 355935 m E 4747127 m N; rel. 4, Mt. Argentella, 355931 m E 4747114 m N.

The specific combination that is characteristic of the new association includes: Geranium argenteum, Festuca violacea subsp. italica, Gentianella columnae, Achillea barrelieri, and Potentilla brauneana. Geranium argenteum is an Alpine–Apennine subendemic species at its southern limit of distribution in the Apennines, and F. violacea subsp. italica, G. columnae, and A. barrelieri subsp. barrelieri are endemic Italian species restricted to the Central Apennines. Finally, P. brauneana is an Alpine–Pyrenaic species first reported in the Sibillini Mountains and new to the Umbrian flora; this species is very rare in the Central Apennines, reaching the southern limit of its distribution in the Mainarde Mountain group (Molise Region) [38]. All these species testify to the high biogeographic value of the new association, which has a strong component of Italian endemic species and subendemic species (25%) (Table S2). The boreal species including Arctic–Alpine species, such as Potentilla crantzii subsp. crantzii, are well represented (15%). Also important is the role of the south-European orophytes (38%), including Southeast European orophytes species exhibiting a strict amphi-Adriatic distribution, such as Carex kitaibeliana. The Mediterranean species such as Sesleria juncifolia are represented well in terms of richness and frequency (11.7% and 9.8%, respectively) but negligible in cover percentage (1.8%) (Table S2).

The classification of the association at a higher syntaxonomic level is quite problematic due to the ecology nature of G. argenteum itself, which is intermediate between four vegetation classes (Carici rupestris-Kobresietea bellardii, Festuco-Seslerietea, Juncetea trifidi, and Thlaspietea rotundifolii) [17,18,19]. Among these, in the area under investigation, the most represented classes are the Carici rupestris-Kobresietea bellardii and Festuco-Seslerietea (Table 1). Based on the classification of the relevé groups of the plant communities in the central Apennines (Figure S1), referred to as the Festuco-Seslerietea (Seslerion apenninae and Carici humilis-Seslerion apenninae alliances) (Figure S1, cluster I) and Carici rupestris-Kobresietea bellardii (Leontopodio nivalis-Elynion myosuroidis alliance) classes (Figure S1, cluster II), the new association Festuco italicae-Geranietum argentei has been referred to the Leontopodio nivalis-Elynion myosuroidis alliance of the Carici rupestris-Kobresietea bellardii class. Among the species identified as characteristic of this alliance are Silene acaulis subsp. bryoides, Achillea barrelieri subsp. barrelieri, Erigeron epiroticus, Leontopodium nivale, and Omalotheca diminuta (the latter reported in Blasi 2003 and Lancioni et al., 2011 [39,40]). Carex kitaibeliana instead assumes the significance of differential species of the Leontopodio nivalis-Elynion myosuroidis alliance compared to Oxytropido-Elynion (Table 1 and Table S1). The species that primarily belong to the class Festuco-Seslerietea highlight the contact of the G. argenteum community with the grasslands of the order Seslerietalia tenuifoliae.

The results of the classification are in accordance with the list of the syntaxa of the Central Apennines reported in the Leontopodio nivalis-Elynion myosuroidis alliance [31], with the exception of the Seslerio apenninae-Dryadetum octopetalae association, which in this classification (Figure S1) is included in the floristic context of the Seslerion apenninae alliance, confirming the original interpretation of the authors [41] and the subsequent revision of Lancioni et al. (2011) [40].

The plant communities included in the Leontopodio nivalis-Elynion myosuroidis alliance (Table S1) may be interpreted as relict communities of the primary alpine tundra on the summits of the highest mountains in the Central Apennines [31], which show an evident alpine belt, such as Gran Sasso [41,42,43] and Majella [39,44,45], while in the Sibillini Mountains, as in other mountain groups in the Central Apennines where the alpine belt is reduced, they appear to be very fragmentary [46,47]. The new Festuco italicae-Geranietum agentei association referred to the Leontopodio nivalis-Elynion myosuroidis represents a further contribution to the knowledge of the alpine vegetation in the Sibillini Mountains and thus in the Central Apennines.

The new plant association refers to the following habitat of community interest (Directive 92/43/EEC Annex I): 6170 “Alpine and subalpine calcareous grasslands” sub-type 36.42 “Wind edge naked-rush swards” (CORINE Biotopes) (corresponding to R45 EUNIS 2019/2021 code).

3.2. Comparison between the Geranium argenteum Communities in the Alpine–Apennine Biogeographical Range

In order to provide a new interpretation of the syntaxonomic framework concerning the communities of G. argenteum within its Alpine–Apennine range and to identify their ecological and floristic characteristics, the new association Festuco italicae-Geranietum argentei from the study area was compared with Salici retusae-Geranietum argentei from the Julian Alps in northwestern Slovenia, Sesleriello sphaerocephalae-Geranietum argentei from the Dolomites Alps, Geranio argentei-Caricetum rupestris from the Tuscan-Emilian Apennines, and the Geranium argenteum group from the Northern Apennines (six relevés, from the Tuscan-Emilian Apennines on siliciclastic substrate, and one from the Apuan Alps (Pania della Croce) on calcareous substrate).

3.2.1. Topography and Geranium argenteum Cover

The Alpine–Apennine communities characterized by G. argenteum are present on snow-covered scree slopes, snow valleys, and windy rocky ridges in an elevation range from 1450 to 2130 m a.s.l., with the highest average values (always above 2000 m a.s.l.) in the pioneer communities of Sesleriello sphaerocephalae-Geranietum argentei (original name: Sesleria sphaerocephala-Geranium argenteum Sutter 1969 ass. prov. (nom. inv. Art. 1)) in the Dolomites and Festuco italicae-Geranietum argentei in the Central Apennines (Table 2). The substrate is calcareous, except for the Geranio argentei-Caricetum rupestris association and Geranium argenteum group in the Northern Apennines (Tuscan-Emilian sector), which are siliciclastic (Table 2). It should be noted that the G. argenteum group includes six relevés from the Tuscan-Emilian Apennines on a siliciclastic substrate and one relevé from the Apuan Alps on calcareous lithologies. On average, the total cover of the species is 75% (the highest in Sesleriello sphaerocephalae-Geranietum argentei), while the average number of species is 26 (the highest in the G. argenteum group). The coverage of G. argenteum (Table 2) reaches significantly high average values in the communities of Festuco italicae-Geranietum argentei followed by that of Salici retusae-Geranietum argentei, while the lowest value was recorded in Geranium argentei-Caricetum rupestris.

3.2.2. Floristic–Vegetational Features with Syntaxonomical Notes

The PCA of the groups of relevés, belonging to the five Alpine–Apennine communities characterized by G. argenteum (Figure 5), underlines the floristic, biogeographic, and syntaxonomic context of the plant communities even more clearly.

Salix retusa and Bistorta vivipara guide the floristic variation along the main PC1 axis (Figure 5A) and characterize the alpine cenoses on calcareous substrates of Salici retusae-Geranietum argentei, differentiated by boreal species and European and south-European orophytes of the Soldanello minimae-Salicion retusae alliance (Arabidetalia coeruleae order), whose association is originally referred to by the authors [17].

Carex rupestris guides the floristic variation along the PC2 axis, with the clear separation of the cenosis of the windy summit ridges of the Northern Apennines (Tuscan-Emilian sector) on a siliciclastic substrate of Geranio argentei-Caricetum rupestris, characterized by the high coverage of Carex rupestris of the Carici rupestris-Kobresietea bellardii class and silicicolous species of the Juncetea trifidii class, including Festuca riccierii, a species endemic to the Northern Apennines [19].

Along the third axis (PC3) of the PCA (Figure 5B), Carex myosuroides guides the floristic variation. There is an evident separation of the Alpine and Apennine pioneer cenoses on the calcareous substrate of the Sesleriello sphaerocephalae-Geranieum argentei and Festuco italicae-Geranietum argentei associations characterized by species of the Carici rupestris-Kobresietea bellardii class and Festuco-Seslerietea class from those on the siliciclastic substrate. In particular, numerous Arctic–Alpine species, typical of the Carici rupestris-Kobresietea bellardii class and Oxytropido-Elynion alliance, are significantly linked to the communities of the alpine windy ridges of Sesleriello sphaerocephalae-Geranietum argentei (Table 3), such as Carex myosuroides, S. acaulis, Dryas octopetala, Chamorchis alpina, and Gentiana nivalis. This may confirm the syntaxonomic classification of the association in the Oxytropido-Elynion alliance (Carici rupestris-Kobresietea bellardii class) as reported by Sutter (1969) [18].

Figure 5. PCA of the relevés belonging to the 5 Geranium argenteum communities (total variance explains 72.2%; eigenvalue and variance explained by the first three axes: PC1 0.13 and 18.2%; PC2 0.08 and 11.2%; PC3 0.07 and 10.1%); only the species significantly linked to the 5 communities derived from the indicator species analysis (Table 3) with score >0.15 are shown. Axes 1–2 (A) and axes 1–3 (B). Information on the weight of each species with respect to the main components identified, as well as the percentage of variance explained by each of them, is shown in Table S3. Abbreviations: Sal-Ger. (Salici retusae-Geranietum argentei); Sesl-Ger. (Sesleriello sphaerocephalae-Geranieum argentei); Ger-Car. (Geranio argentei-Caricetum rupestris); Fest-Ger. (Festuco italicae-Geranietum argentei, study area); Ger. gr. (Geranium argenteum group). The full names of the abbreviated species in the figure are reported in Table 3.

In addition to the boreal species of the Carici-Kobresietea class, such as P. crantzii subsp. crantzii and Sedum atratum, the Italian endemic (Achillea barrelieri) and subendemic species (Leontopodium nivale), Mediterranean elements (Erigeron epiroticus), and south-European orophytes species (Omalotheca diminuta, Carex kitaibeliana) that do not reach the Alps are significantly linked to the pioneer calcicolous communities of Festuco italicae-Geranietum argentei (Table 1 and Table 3) in the Central Apennines that, in turn, are also characteristics and differentials of the Leontopodio nivalis-Elynion myosuroidis Central Apennines alliance to which the association refers.

Regarding the G. argenteum group communities of the Northern Apennines (Tuscan-Emilian Apennines and Apuan Alps sectors), ranging from the upper supratemperate to the lower orotemperate thermotype, there are significant species (Table 3) of the Festuco-Seslerietea (e.g., Sesleria juncifolia complex) and Festuco-Brometea classes (e.g., Cerastium arvense subsp. suffruticosum). To these, exclusively on siliciclastic substrate (Tuscan-Emilian sector), the species of Nardetea strictae classes are added (e.g., Antennaria dioica), and those of the Juncetea trifidi classes (e.g., Agrostis rupestris) and Loiseleurio-Vaccinietea classes (e.g., Vaccinium uliginosum), which indicate the connection with the cenoses of Geranium argentei-Caricetum rupestris of the highest elevation. An exception is the only relevé from the Apuan Alps [11], on a calcareous substrate in which the acidophilic species typical of siliciclastic rocks of the Nardetea strictae, Juncetea trifidi, and Louseleurio-Vaccinetea classes are practically absent.

Table 3. Species significantly linked to the plant communities characterized by Geranium argenteum deriving from the indicator species analysis (p value < 0.05, significance codes: *** ≤ 0.001, ** ≤ 0.01, * ≤ 0.05; column A is the positive predictive value of the species as indicator of the site group; column B is the sensitivity of the species as indicator of the target site group). The diagnostic species indicated in the original description of the association are underlined.

Plant Association	Abbrev.	A	B	Stat.	p Value		* Syntaxonomical Reference
Salici retusae-Geranietum argentei (Eastern Alps; Julian Alps)
Salix retusa L.	Sal.retu	1.000	0.813	0.901	0.001	***	Thlaspietea rotundifolii
Trifolium pallescens Schreb.	Tri.pal	1.000	0.875	0.935	0.001	***	Thlaspietea rotundifolii
Soldanella alpina L.	Sol.alp	0.747	0.500	0.611	0.028	*	Thlaspietea rotundifolii
Bistorta vivipara (L.) Delarbre	Bis.viv	0.603	0.875	0.726	0.001	***	Carici rupestris-Kobresietea bellardii
Gentianella anisodonta (Borbás) Á. Löve et D. Löve	Gen.ani	1.000	0.688	0.829	0.001	***	Festuco-Seslerietea
Geranium argenteum L.	Ger.arg	0.306	1.000	0.553	0.001	***	Festuco-Seslerietea
Erigeron glabratus Hoppe et Hornsch. ex Bluff et Fingerh.	Eri.gla	1.000	0.438	0.661	0.013	*	Festuco-Seslerietea
Festuca nitida Kit. ex Schult. subsp. nitida	Fes.nit	1.000	0.438	0.661	0.015	*	Festuco-Seslerietea
Galium anisophyllon Vill.	Gal.ani	0.549	0.625	0.586	0.043	*	Festuco-Seslerietea
Anthoxanthum nipponicum Honda	Ant.nip	1.000	0.500	0.707	0.009	**	Juncetea trifidii
Parnassia palustris L.	Par.pal	1.000	0.875	0.935	0.001	***	Other
Sesleriello sphaerocephalae-Geranietum argentei (Eastern Alps; Dolomites)
Carex capillaris L.	Car.cap.	0.727	0.428	0.558	0.047	*	Carici rupestris-Kobresietea bellardii
Dryas octopetala L. subsp. octopetala	Dry.oct	0.926	0.714	0.813	0.001	***	Carici rupestris-Kobresietea bellardii
Silene acaulis (L.) Jacq. (s.l.)	Sil.aca	0.901	0.857	0.879	0.001	***	Carici rupestris-Kobresietea bellardii
Carex myosuroides Vill. (Elyna myosuroides (Vill.) Fritsch)	Car.myo	1.000	0.714	0.845	0.002	**	Carici rupestris-Kobresietea bellardii
Chamorchis alpina (L.) Rich.	Cha.alp	1.000	0.714	0.845	0.002	**	Carici rupestris-Kobresietea bellardii
Festuca pumila Chaix	Fes.pum	1.000	0.429	0.655	0.020	*	Carici rupestris-Kobresietea bellardii
Gentiana nivalis L.	Gen.niv	0.821	0.429	0.593	0.033	*	Carici rupestris-Kobresietea bellardii
Helianthemum oelandicum (L.) Dum. Cours. subsp. alpestre (Jacq.) Ces.	Hel.oel.alp	0.677	1.000	0.823	0.001	***	Festuco-Seslerietea
Anthyllis vulneraria L. subsp. alpicola (Brügger) Gutermann	Ant.vul.alp	1.000	0.571	0.756	0.001	***	Festuco-Seslerietea
Dianthus sternbergii Sieber ex Capelli	Dia.ste	1.000	0.571	0.756	0.004	**	Festuco-Seslerietea
Sesleria caerulea (L.) Ard.	Ses.cae	1.000	0.857	0.926	0.002	**	Festuco-Seslerietea
Sesleriella sphaerocephala (Ard.) Deyl (Sesleria sphaerocephala Ard.)	Ses.sph	1.000	0.571	0.756	0.003	**	Festuco-Seslerietea
Selaginella selaginoides (L.) P. Beauv. ex Schrank et Mart.	Sel.sel	0.746	0.571	0.653	0.023	*	Festuco-Seslerietea
Carex firma Host	Car.fir	0.889	0.429	0.617	0.035	*	Festuco-Seslerietea
Cherleria sedoides L.	Che.sed	0.774	0.429	0.576	0.044	*	Juncetea trifidii
Saxifraga crustata Vest.	Sax.cru	1.000	0.714	0.845	0.001	***	Asplenietea trichomanis
Oxytropis carinthica Fischer	Oxy.car	1.000	0.429	0.655	0.017	*	Other
Polygala chamaebuxus L.	Pol.cha	1.000	0.429	0.655	0.027	*	Other
Geranio argentei-Caricetum rupetris (Northern Apennines)
Carex rupestris All.	Car.rup	0.901	1.000	0.949	0.001	***	Carici rupestris-Kobresietea bellardii
Aster alpinus L. subsp. alpinus	Ast.alp	0.549	0.800	0.663	0.014	*	Festuco-Seslerietea
Alchemilla transiens (Buser) Buser	Alc.tra	1.000	0.800	0.894	0.001	***	Juncetea trifidii
Festuca riccerii Foggi et Gr. Rossi	Fes.ric	1.000	0.600	0.775	0.002	**	Juncetea trifidii
Luzula lutea (All.) DC. subsp. lutea	Luz.lut	0.808	0.600	0.696	0.004	**	Juncetea trifidii
Alchemilla flabellata Buser	Alc.fla	0.535	0.800	0.654	0.022	*	Juncetea trifidii
Geranium argenteum group (Northern Apennines)
Campanula cochleariifolia Lam.	Cam.coc	1.000	0.571	0.756	0.002	**	Thlaspietea rotundifolii
Anemonastrum narcissiflorum (L.) Holub	Ane.nar	0.920	0.714	0.810	0.002	**	Festuco-Seslerietea
Sesleria juncifolia Wulfen ex Suffren subsp. juncifolia	Ses.jun	0.767	0.714	0.740	0.002	**	Festuco-Seslerietea
Alchemilla cinerea Buser	Alc.cin	1.000	0.857	0.926	0.001	***	Festuco-Seslerietea
Achemilla alpina L. Series saxatiles Buser	Ach.alp	1.000	0.857	0.926	0.001	***	Juncetea trifidii
Oreojuncus trifidus (Jacq.) Záv. Drábk. et Kirschner	Ore.tri	1.000	0.429	0.655	0.027	*	Juncetea trifidii
Pedicularis tuberosa L.	Ped.tub	1.000	0.429	0.655	0.025	*	Juncetea trifidii
Phyteuma hemisphaericum L.	Phy.hem	0.811	0.429	0.589	0.040	*	Juncetea trifidii
Agrostis rupestris All.	Agr.rup	0.616	0.571	0.594	0.028	*	Juncetea trifidii
Viola cavillieri W. Becker	Vio.cav	1.000	0.429	0.655	0.013	*	Juncetea trifidii
Gentianella campestris (L.) Börner	Gen.cam	1.000	0.429	0.655	0.018	*	Loiseleurio-Vaccinietea
Juniperus communis L. subsp. nana (Willd.) Syme	Jun.com.nan	1.000	0.429	0.655	0.025	*	Loiseleurio-Vaccinietea
Vaccinium uliginosum L. subsp. microphyllum (Lange) Tolm.	Vac.uli	0.821	0.429	0.593	0.035	*	Loiseleurio-Vaccinietea
Antennaria dioica (L.) Gaertn.	Ant.dio	1.000	0.571	0.756	0.004	**	Nardetea strictae
Avenella flexuosa (L.) Parl. subsp. flexuosa	Ave.fle	1.000	0.571	0.756	0.002	**	Nardetea strictae
Cynanchica aristata (L. f.) P. Caputo et Del Guacchio (s.l.)	Asp.ari	1.000	0.714	0.845	0.001	***	Festuco-Brometea
Brachypodium genuense (DC.) Roem. et Schult.	Bra.gen	1.000	0.857	0.926	0.001	***	Festuco-Brometea
Festuca laevigata Gaudin subsp. laevigata	Fes.lae	1.000	0.857	0.926	0.001	***	Festuco-Brometea
Cerastium arvense L. subsp. suffruticosum (L.) Ces.	Cer.arv	0.667	0.857	0.756	0.002	**	Festuco-Brometea
Euphrasia stricta D. Wolff ex J.F. Lehm.	Eup.str	1.000	0.571	0.756	0.003	**	Festuco-Brometea
Pilosella officinarum Vaill.	Hie.pil	1.000	0.571	0.756	0.002	**	Festuco-Brometea
Poa alpina L. subsp. alpina	Poa.alp	0.692	1.000	0.832	0.001	***	Other
Luzula campestris (L.) DC.	Luz.cam	1.000	0.571	0.756	0.002	**	Other
Carum carvi L.	Caru.car	1.000	0.429	0.655	0.026	*	Other
Leucanthemum coronopifolium Vill. (s.l.)	Leu.cor	1.000	0.429	0.655	0.013	*	Other
Rosa pendulina L.	Ros.pen	1.000	0.429	0.655	0.018	*	Other
Vaccinium myrtillus L.	Vac.myr	0.714	0.571	0.639	0.022	*	Other
Festuco italicae-Geranietum argentei (Central Apennines)
Doronicum columnae Ten.	Dor.col	1.000	0.750	0.866	0.002	**	Thlaspietea rotundifolii
Sabulina verna (L.) Rchb. subsp. verna	Sab.ver	0.778	1.000	0.882	0.001	***	Carici rupestris-Kobresietea bellardii
Sedum atratum L.	Sed.atr	0.875	1.000	0.935	0.001	***	Carici rupestris-Kobresietea bellardii
Potentilla crantzii (Crantz) Beck ex Fritsch subsp. crantzii	Pot.cra	0.435	1.000	0.660	0.011	*	Carici rupestris-Kobresietea bellardii
Achillea barrelieri (Ten.) Sch. Bip. subsp. barrelieri	Ach.bar	1.000	0.750	0.866	0.001	***	Leontopodio nivalis-Elynion myosuroidis
Erigeron epiroticus (Vierh.) Halácsy	Eri.epi	1.000	0.750	0.866	0.001	***	Leontopodio nivalis-Elynion myosuroidis
Silene acaulis (L.) Jacq. subsp. bryoides (Jord.) Nyman	Sil.aca.bri	0.840	1.000	0.917	0.001	***	Leontopodio nivalis-Elynion myosuroidis
Leontopodium nivale (Ten.) Hand.-Mazz.	Leo.niv	1.000	0.500	0.707	0.007	**	Leontopodio nivalis-Elynion myosuroidis
Omalotheca diminuta (Braun-Blanq.) Bartolucci et Galasso	Oma.dim	1.000	0.500	0.707	0.005	**	Leontopodio nivalis-Elynion myosuroidis
Carex kitaibeliana Degen ex Bech.	Car.kit	1.000	1.000	1.000	0.001	***	Festuco-Seslerietea
Edraianthus graminifolius (L.) A. DC. subsp. graminifolius	Edr.gra	1.000	0.750	0.866	0.001	***	Festuco-Seslerietea
Ranunculus breyninus Crantz	Ran.bre	1.000	1.000	1.000	0.001	***	Festuco-Seslerietea
Alchemilla nitida Buser	Alc.nit	1.000	0.500	0.707	0.007	**	Festuco-Seslerietea
Draba aizoides L. subsp. aizoides	Dra.aiz	0.840	0.750	0.794	0.003	**	Festuco-Seslerietea
Pulsatilla alpina (L.) Delarbre subsp. millefoliata (Bertol.) D.M. Moser	Pul.alp	1.000	0.500	0.707	0.010	**	Festuco-Seslerietea
Festuca violacea Ser. ex Gaudin subsp. italica Foggi, Gr. Rossi et Signorini	Fes.vio	1.000	1.000	1.000	0.001	***	Festuco-Seslerietea
Plantago atrata Hoppe subsp. atrata	Pla.atr	1.000	1.000	1.000	0.001	***	D Nardetea strictae
Taraxacum apenninum (Ten.) DC.	Tar.ape	1.000	0.750	0.866	0.001	***	Nardetea strictae
Crepis aurea (L.) Cass. subsp. glabrescens (Caruel) Arcang.	Cre.aur	0.710	0.750	0.730	0.003	**	Nardetea strictae
Campanula tanfanii Podlech	Cam.tan	1.000	0.500	0.707	0.010	**	Asplenietea trichomanis
Asplenium viride Huds.	Asp.vir	0.778	0.500	0.624	0.035	*	Asplenietea trichomanis
Globularia meridionalis (Podp.) O. Schwarz	Glo.mer	1.000	0.750	0.866	0.001	***	Festuco-Brometea
Helictochloa praetutiana (Parl. ex Arcang.) Bartolucci, F. Conti, Peruzzi et Banfi subsp. praetutiana	Hel.pra	1.000	0.750	0.866	0.001	***	Festuco-Brometea
Koeleria australis A. Kern	Koe.aus	1.000	0.750	0.866	0.001	***	Festuco-Brometea
Armeria gracilis Ten. subsp. gracilis	Arm.gra	0.814	1.000	0.902	0.001	***	Other
Gentianella columnae (Ten.) Holub	Gen.col	1.000	1.000	1.000	0.001	***	Other
Poa molinerii Balb.	Poa.mol	1.000	1.000	1.000	0.001	***	Other
Potentilla brauneana Hoppe	Pot.bra	1.000	0.750	0.866	0.001	***	Other
Saxifraga adscendens L. subsp. adscendens	Sax.ads	1.000	1.000	1.000	0.001	***	Other
Cystopteris fragilis (L.) Bernh.	Cys.fra	0.923	0.750	0.832	0.002	**	Other
Anthyllis vulneraria L. subsp. nana (Ten.) Tammaro	Ant.vul.nan	1.000	0.500	0.707	0.011	*	Other

Original data source: Salici retusae-Geranietum argentei Surina 2005 from Table 11: rels. 1–16 in Surina (2005), Krn Mountain (Julian Alps) in northwestern Slovenia; Sesleriello sphaerocephalae-Geranietum argentei Sutter ex Ballelli, Tesei, Pennesi et Allegrezza ass. nova from Table II: rels. 1–3 in Sutter (1969) [18], Mt. Serva Dolomites Alps, and from Table 11: rels. 1, 10, 11, 12 in Pignatti and Pignatti (2016) [10], Mt. Serva, Mt. Cavallo, Mt. Lastè, Dolomites Alps; Geranio argentei-Caricetum rupestris Tomaselli et al., 2019 from Table 4: rels. 1–5 in Tomaselli et al. (2019) [19], Mt. Cimone, Tuscan-Emilian Apennines (Northern Apennines); Geranium argenteum group: 7 rels. in Cortopassi thesis (2007) [11] from Northern Apennines, of which 6 rels. from Tuscan-Emilian Apennines (Mt. Vecchio; Mt. Corno alle Scale; Mt. Spogolino) are on siliciclastic substrate and the one rel. from Apuan Alps (Pania della Croce) is on calcareous substrate; Festuco italicae-Geranietum argentei ass. nova from Table 1: rels. 1–4 in this paper (study area, Central Apennines).

3.3. Validations of Syntaxa

Sesleriello sphaerocephalae-Geranietum argentei Sutter ex Ballelli, Tesei, Pennesi et Allegrezza ass. nova (typus rel. 1, Table II, p. 356, in Sutter 1969)

Valitaded name: “Sesleria sphaerocephala-Geranium argenteum-Ass. prov.” in Sutter (1969, p. 356) [18] (Art. 3b).

Synonym: Seslerio sphaerocephalae-Geranietum argentei Sutter 1969 (nom. inv. Art. 3b); Seslerio caeruleae-Geranietum argentei Sutter 1969 (nom. inv. Art. 3b).

Diagnostic taxa of the association are reported in Table II, p. 356 in Sutter (1969 [18]). They are: Geranium argenteum L., Carex capillaris L., Carex myosuroides Vill., Dianthus sternbergii Sieber ex Capelli, Sesleriella sphaerocephala (Ard.) Deyl (Sesleria sphaerocephala Ard.), and Oxytropis carinthica Fischer.

3.4. General Syntaxonomic Scheme for Alpine–Apennines Communities Considered for the Comparison

CARICI RUPESTRIS-KOBRESIETEA BELLARDII Ohba 1974

+Oxytropido-Elynetalia Albrecht 1969

*Oxytropido-Elynion myosuroidis Br.-Bl. 1950

Sesleriello sphaerocephalae-Geranietum argentei Sutter ex Ballelli, Tesei, Pennesi et Allegrezza ass. nova

Geranio argentei-Caricetum rupestris Tomaselli, Carbognani, Foggi, Petraglia, Rossi, Lombardi et Gennai 2019

*Leontopodio nivalis-Elynion myosuroidis (Blasi et Di Pietro in Blasi, Di Pietro, Fortini et Catonica 2003) Di Pietro et Mucina in Chytry, Danlël, Di Pietro, Koroleva et Mucina 2015

Festuco italicae-Geranietum argentei ass. nov.

THLASPIETEA ROTUNDIFOLII Br.-Bl. 1948

+Arabidetalia coeruleae Rübel ex Nordhagen 1936

*Arabidion caeruleae Br.-Bl. in Br.-Bl. et Jenny 1926

(=Soldanello alpinae-Salicion retusae Englisch 1999 (syntax. syn.)

Salici retusae-Geranietum argentei Surina 2005

FESTUCO-SESLERIETEA Barbéro-Bonin 1969

+Seslerietalia tenuifoliae Horvat 1930

Geranium argenteum group

3.5. Climate Change and Plant Community Conservation Notes

Climate change has a high negative impact on high-altitude habitats, especially in the Mediterranean area where the few isolated mountain peaks host plant associations characterized by endemic and rare species (e.g., Pauli et al., 2003) [48] with a narrow and fragmented areal [49]. The potential impact of climate change on the fragile and narrowly restricted G. argenteum plant association in the study area could alter its floristic composition and lead to its extinction. As observed in the short and long term (e.g., Frate et al., 2018) [50], climatic warming has determined the reduction in typically cryophilous species and the upward shift of thermophilous species from the lower vegetation belt (e.g., Korner 2021) [51], a process described as thermophilization (e.g., Stanisci et al., 2011) [52]. Recently, the decline of the alpine cushion plant Silene acaulis at its southern limit of distribution in the Apennines was documented by Bonanomi et al., 2023 [53] as being strongly linked to particularly intense heatwaves. The vulnerability of high-altitude species such as G. argenteum is also amplified by the high fragmentation of the species at its southern limit of distribution and the absence of specific dispersal mechanisms (mean dispersal distance <1 m) [54]. Dispersal distance can play a key role in the persistence and survival of rare species confined to particular microhabitats, as demonstrated by seven endangered and vulnerable taxa in the central Apennines [49]. In order to conserve the microhabitats that host the G. argenteum plant community in the study area, it will be essential to monitor over time any changes in the floristic composition of the community and the population size of G. argenteum. In particular for G. argenteum, it is also important to collect seeds for ex situ conservation for possible population reinforcement.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/life13122273/s1, Figure S1: Dendrogram obtained from the classification of the relevés groups of the Central Apennines communities, from the high mountain to alpine belts; Table S1: Synoptic table of the plant communities occurring in the alpine and subalpine belts of the Central Apennines; Table S2: Chorological spectrum concerning the species of the new plant association Festuco italicae-Geranietum argentei; Table S3: Weight of species and the relative % of variance explained by each one.

Author Contributions

Conceptualization, M.A., S.B. and G.T.; validation, M.A., S.B., G.T. and R.P.; formal analysis and data curation, G.T.; writing—original draft preparation, M.A. and G.T.; supervision, M.A.; writing—review and editing, M.A., S.B., G.T. and R.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data generated or analyzed during this study are included in this published article and its supplementary information files.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Geographical distribution map of Geranium argenteum. Circles (●) indicate the presence of G. argenteum, the triangles (▲) indicate the current position of the sites where the communities have been described.

Figure 2. Plant landscape of the study area (the red stars indicate the locations of the relevés).

Figure 3. The typical habitat of the G. argenteum in the study area.

Figure 4. G. argenteum close-up of flowering (a) and G. argenteum community in the study area on the fractured rocky ridges (b).

Table 2. Topographical, biological, and distributive parameters of the communities characterized by Geranium argenteum. Higher values are indicated in bold. Abbreviations: Sal-Ger. (Salici retusae-Geranietum argentei); Sesl-Ger. (Sesleriello sphaerocephalae-Geranietum argentei); Ger. gr. (Geranium argenteum group); Ger-Car. (Geranio argentei-Caricetum rupestris); Fest-Ger. (Festuco italicae-Geranietum argentei, study area).

Geography	Alps		Apennines
Geography	Julian	Dolomites	Northern	Northern	Central
Plant communities	Sal-Ger.	Sesl-Ger.	Ger-Car.	Ger. gr.	Fest-Ger.
No. of relevés	16	7	5	7	4
Mean Elevation (m. a.s.l.)	1806	2105	1988	1818	2058
Mean Slope (°)	16.3	51.7	12.0	39.0	35.0
Substrate (C: calcareous; S: siliciclastic)	C	C	S	S, C	C
Mean Species Cover (%)	87.5	93.3	90.0	42.1	60.0
Mean richness	17.0	29.4	10.0	38.0	34.0
Geranium argenteum mean cover (%)	38.0	15.0	4.2	7.3	44.4
Chorological type mean richness (%)
Endemic	14.5	19.8	21.1	19.5	30.0
Boreal	31.6	26.4	26.3	17.9	13.3
South-European orophytes	32.9	36.3	36.8	34.1	38.3
European orophytes	11.8	8.8	5.3	1.6	3.3
Mediterranean	1.3	4.4	5.3	5.7	8.3
Eurasian	5.3	4.4	5.3	16.3	3.3
Cosmopolitan	2.6	0.0	0.0	4.9	3.3

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Ballelli, S.; Tesei, G.; Pennesi, R.; Allegrezza, M. Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines. Life 2023, 13, 2273. https://doi.org/10.3390/life13122273

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Ballelli S, Tesei G, Pennesi R, Allegrezza M. Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines. Life. 2023; 13(12):2273. https://doi.org/10.3390/life13122273

Chicago/Turabian Style

Ballelli, Sandro, Giulio Tesei, Riccardo Pennesi, and Marina Allegrezza. 2023. "Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines" Life 13, no. 12: 2273. https://doi.org/10.3390/life13122273

APA Style

Ballelli, S., Tesei, G., Pennesi, R., & Allegrezza, M. (2023). Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines. Life, 13(12), 2273. https://doi.org/10.3390/life13122273

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Floristic–Vegetational Features of Geranium argenteum, an Alpine–Apennine Species at Its Limit of Distribution in the Apennines

Abstract

1. Introduction

2. Materials and Methods

2.1. Study Area

2.2. Vegetation Study

2.3. Statical Analysis

3. Results and Discussion

3.1. Geranium argenteum Community in the Study Area

3.2. Comparison between the Geranium argenteum Communities in the Alpine–Apennine Biogeographical Range

3.2.1. Topography and Geranium argenteum Cover

3.2.2. Floristic–Vegetational Features with Syntaxonomical Notes

3.3. Validations of Syntaxa

3.4. General Syntaxonomic Scheme for Alpine–Apennines Communities Considered for the Comparison

3.5. Climate Change and Plant Community Conservation Notes

Supplementary Materials

Author Contributions

Funding

Institutional Review Board Statement

Informed Consent Statement

Data Availability Statement

Conflicts of Interest

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