The study area is included within the municipality of Cittareale (province of Rieti), belonging to the Lazio administrative region. It extends for 343 ha, at altitudes ranging between 1150 and 1903 m a.s.l. (Fig. 1). The study area includes the peak of Mt. Pozzoni (1903 m), extends to southeast including the mountain ridge of Mt. Laghetto-Mt. Prato (1834 m), ending in the south almost in correspondence of the provincial road Cittareale-Norcia. To the west the limit runs along the watershed that delimits the valley of St. Rufo-Pozzoni (Fig. 1).

Figure 1. 

Study area location (a) and its landscape (c–e) b the limits of study area drawn on I.G.M.I-1:25,000 topographic map c high mountain pastures of Mt. Pozzoni dominated by Brachypodium genuense (DC.) Roem. et Schult. with Trifolium alpestre L. e Fritillaria montana Hoppe ex W.D.J.Koch, a rare species considered “Near Threatened” for extinction risk. Photos: R. Tranquilli and E. Del Vico.

The substrate is mainly made up of Meso-Cenozoic marly limestone (“Scaglia” formation) belonging to the Umbria-Marche succession; these sedimentary layers are heavily fractured and faulted, due to the proximity of a regional overthrust overlapping the Sibillini unit on the Gran Sasso-Cittareale unit (Calamita et al. 1995). The head of the valley is modeled by an evident glacial cirque, with a threshold placed at an altitude of 1660 m; the valley bottom is largely covered with slope debris, mixed with sediments of fluvio-glacial origin partly terraced and dissected by the upper course of Velino River. Along St. Rufo valley, an important karst cavity, 3 km long and over 400 m deep, opens at about 1440 m set in the marly limestones of Scaglia rossa formation (Gatti and Uffreduzzi 1989); the cavity has returned interesting fossil remains of bats, testifying to a cold period fauna dated to the end of the Pleistocene (Argenti et al. 2008).

Following the bioclimatic classification of Rivas-Martínez et al. (2011), the climate is Temperate oceanic/semi-continental, with the presence of two phytoclimatic belts along the altitudinal gradient, from the lower supratemperate to the lower orotemperate of the cacuminal areas; ombrotypes are comprised between humid and hyperhumid (Pesaresi et al. 2017).

The land cover is dominated by secondary grasslands, deciduous woodlands and small patches of artificial coniferous forest. Meadows and fallows are very limited and arable lands are nowadays completely missing in the study area. In the past they must have been quite common in the lower part of the valley, as evidenced by the presence of several still visible terraced parcels. Forests are used regularly as coppices and summer grazing of cattle and sheep is still widespread in this sector, together with horse grazing, which is conversely continuously present almost all year round.

The study area does not comprise any protected area, even if some Natura 2000 sites, defined according to European Union Habitat Directive (European Union 1992), are present in the neighboring territory of the Umbria region.

The flora of the studied area was investigated in depth by carrying out numerous herborizations and field excursions, both in spring, summer and autumn, during three consecutive years from 2008 to 2010. Identification of vascular plants was mostly based on Pignatti (1982) and Flora Europaea (Tutin et al. 1968, 1972, 1976, 1980, 1993). Taxa delimitation was based on Anzalone et al. (2010) and nomenclature accords to Bartolucci et al. (2018), Galasso et al. (2018) and the subsequent updates summarized in the “Portal to the Flora of Italy” (http://dryades.units.it/floritaly/). Families of vascular plants correspond to APG IV (2016), whereas life forms and chorotypes were retrieved from Pignatti (1982). Exsiccata are preserved in Herbarium Lucanum (HLUC), Herbarium Del Vico (Roma) and Herbarium Lattanzi (Roma), the latter is now moving to Herbarium Sapienza (RO). In the floristic list we reported the rarity level in the regional flora of Lazio for each taxon according to Anzalone et al. (2010), adopting three levels: rare, medium rare and very rare (coded as R, MR, RR). New taxa for the regional flora were marked with an asterisk. Italian endemics were retrieved from Bartolucci et al. (2018). As for alien taxa, we also reported the status of naturalization in the study area following the same codes used by Galasso et al. (2018). For each taxon the status of threatened species was derived by the published Italian Red lists (Conti et al. 1992, 1997) and updated, when new assessments were available, according to the most recent ones (Rossi et al. 2013; Orsenigo et al. 2020). Vegetation was analyzed using the phytosociological method (Braun-Blanquet 1965) by carrying out 30 surveys of the main vegetation types in the territory located in the field with a GPS unit with ± 5 m accuracy. The syntaxonomic nomenclature, at the level of alliance, order and class, follows the ‘Prodrome of the Italian Vegetation’ (Biondi et al. 2014).

Main vegetation types were identified through multivariate methods, Hierarchical Cluster Analysis and NMDS ordination. For each vegetation type a floristic-ecological description and the syntaxonomic framework were provided.

794 taxa of vascular plants were identified, belonging to 331 genera and 69 families (Appendix 1). The families with more than 40 taxa (Fig. 2a) were: Asteraceae (107), Poaceae (71), Fabaceae (67), Caryophyllaceae (46) and Rosaceae (42). The most diverse genera were Trifolium (19), Carex (16), Ranunculus (14), Hieracium (13) and Silene (12) (Fig. 2b). Hemicryptophytes were the dominant life form (52%), followed by therophytes (21%) and geophytes (13%) (Fig. 2c). As for chorology, (Fig. 2d) species with Eurasian-Paleotemperate distribution prevailed (39%), slightly exceeding the Mediterranean element (29%). The Mediterranean group was mainly composed of Eurimediterranean (15%) and Mediterranean-Mountain species (6%). A significant contingent of Circumboreal species was also present (6%) while only a few species displayed eastern chorotypes (e.g. SE-European and Pontic).

Figure 2. 

a number of taxa per family; only the families with more than 10 taxa are shown b number of taxa per genus; genera containing more than 7 taxa are shown c life form percentages d chorological spectrum of the detected flora in the study area.

Forty-seven taxa, approximately 6% of the total, were found to be endemic to Italy (Table 1). Only eight taxa were found to be aliens, among these Malus domestica (Suckow) Borkh., Matricaria discoidea DC., Medicago sativa L. and Veronica persica Poir. can be considered naturalized, whereas Abies alba Mill., Abies cephalonica Loudon, Picea abies (L.) H. Karst. and Pinus nigra J.F. Arnold subsp. nigra have been observed only as planted in reforested areas.

Two taxa, Arum cylindraceum Gasp. and Corydalis densiflora C.Presl subsp. apennina F.Conti, Bartolucci & Uzunov have been recorded for the first time for Lazio during this research, whereas four taxa whose presence was considered doubtful for Lazio have been confirmed (Alopecurus pratensis L. subsp. pratensis, Hieracium bupleuroides C.C.Gmel., Scandix macrorhyncha C.A.Mey and Trisetaria flavescens (L.) Baumg. subsp. flavescens). These floristic records at regional level have been anticipated by Del Vico et al. (2014). However, probably due to oversight, Alopecurus pratensis subsp. pratensis is still considered to be confirmed for Lazio in the continuously updated database of the Portal to the Flora of Italy (Available at http:/dryades.units.it/floritaly, accessed: 16/11/2020). Additionally, we herein confirm the presence of Trinia glauca (L.) Dumort. subsp. glauca, previously considered recorded erroneously for Lazio (Bartolucci et al. 2018).

Thirty-four taxa (Table 2) are considered very rare at the regional level (2010). Considering all the rare species (R, MR and RR), these taxa represent altogether approximately 20% of the studied flora.

The following 15 species have been identified as being at risk of extinction in the first published Italian red lists (Conti et al. 1992, 1997): Iris marsica I. Ricci et Colas., Achillea tomentosa L., Carex panicea L., Fritillaria montana Hoppe ex Koch, Gentiana lutea L. subsp. lutea, Gentiana utriculosa L., Klasea nudicaulis (L.) Fourr., Lathyrus nissolia L., Lilium bulbiferum L. subsp. croceum (Chaix) Jan, Narcissus poëticus L., Onobrychis arenaria (Kit.) DC. subsp. arenaria, Ornithogalum comosum L., Scorzonera purpurea L., Trifolium phleoides Willd. and Trisetaria villosa (Bertol.) Banfi et Soldano. Meanwhile, in the most recent ones (Rossi et al. 2013; Orsenigo et al. 2020), excluding the species classified as “Least Concern”, Viola kitaibeliana Schult. was listed as “Endangered”, Epipactis meridionalis H. Baumann et R. Lorenz as “Vulnerable” and Fritillaria montana, Gentiana lutea, Iris marsica and Senecio scopolii Hoppe et Hornsch. ex Bluff et Fingerh. as “Near Threatened”.

Hierarchical cluster analysis and NMDS ordination (the latter not shown) enabled the detection of 10 clusters that were clearly interpretable, floristically and ecologically, as shown in Fig. 3. A further inspection of the ordered table led to the identification of 12 plant communities (some of these represented by only one relevè); the greatest phytocoenotic diversity was found within the secondary pastures. The relevès of these communities are presented in Suppl. material 1: Table S1 and described in detail below.

Figure 3. 

Hierarchical clustering resulting from Modified TWINSPAN analysis. Cluster 1) Fagus sylvatica woodlands; 2) Amelanchier ovalis forest edges; 3) Saxifraga callosa chasmophytic vegetation; 4) Cynosurus cristatus hay meadows; 5) Bromopsis erecta montane grasslands; 6) Iris marsica community; 7) Rumex scutatus screes vegetation; 8) Paronychia kapela rocky outcrops vegetation; 9) upper-montane grasslands, including also the Brachypodium genuense community and the Astragalus sempervirens community; 10) chamaephytes-rich dry grasslands.

Forest vegetation in the Mt. Pozzoni valley is represented almost exclusively by beech forests (cluster 1). Quercus cerris woodlands are present only on the edges of the investigated area on southern exposures, but they are widespread at lower altitudes where flyschoid substrates emerge. Small patches of coniferous plantation, planted for reforestation purposes (e.g. Pinus nigra, Abies spp.) are also present. Fagus sylvatica forests cover approx. 60 ha, forming a more or less continuous belt between 1350 and 1700 m a.s.l.; they are managed as coppices with stands, meanwhile mixed aged and old-growth formations are absent. Tree layer is always dominated by Fagus sylvatica, frequently accompanied by Acer pseudoplatanus and Acer opalus subsp. obtusatum. In relevè no. 1, surveyed at 1500 m, in the tree layer we also found Tilia plathyphyllos and Prunus avium, while in rel. no. 2, placed at 1360 m, the presence of Quercus cerris and Acer campestre can be noted. In the herb layer, nemoral species commonly found in mesic and beech forests are present, such as Cardamine bulbifera, Pulmonaria vallarsae subsp. apennina, Moehringia trinervia, Rabelera holostea (= Stellaria holostea); from a phytosociological point of view most of these species are typical of Fagetalia sylvaticae order. Related to the altitude, the second relevè in table S1 hosts a larger contingent of species having a relatively thermophilic character, such as Lathyrus venetus, Cyclamen hederifolium, Cephalanthera damasonium, Sesleria autumnalis, Viola odorata, which also characterize the lower altitudinal vegetation belt dominated by oak forests. These relevès can be classified in the alliance Aremonio agrimonioidis-Fagion sylvaticae (Querco roboris-Fagetea sylvaticae, Fagetalia sylvaticae) describing the beech forests of E-Europe, Balkans and extending to Central-Northern Apennine (Biondi et al. 2014). The beech woods at lower altitudes, as evidenced by the relevè no. 2, show a floristic composition referable to Lathyro veneti-Fagetum sylvaticae, a widespread association which frames beech forests of lower supratemperate belt of the Central Apennines mainly on limestones (Blasi et al. 2010). At higher altitudes, generally above 1500 m, it is possible to observe a clear decrease in the number of species of Quecetalia pubescenti-petraeae, indicating a shift towards the association Cardamino kitaibelii-Fagetum sylvaticae Ubaldi ex Ubaldi 1995. The latter represents the potential vegetation of the upper supratemperate belt, which in the St. Rufo valley is almost completely substituted by the secondary grasslands belonging to Festuco-Brometea class.

The edge of the beech forest (cluster 2), in some cases, presents characteristic pre-forest shrub formations, as evidenced by relevè no. 3, physiognomically dominated by Amelanchier ovalis, Atadinus fallax (=Rhamnus alpina subsp. fallax) and Sorbus aria, accompanied by smaller shrubs of Rosa montana, Crataegus laevigata and Cytisophyllum sessilifolium. These formations can be attributed to the association Rhamno alpinae-Amelanchieretum ovalis (Berberidion vulgaris, Prunetalia spinosae, Rhamno-Prunetea), described for Sibillini mountains by Pedrotti (1994) and revised by Cutini et al. (2002), even if the herb layer appeared strongly impoverished.

Along the river incisions, especially in the middle and lower part of the investigated area, there are other shrub and pre-forest formations of difficult syntaxonomic classification at association level, dominated by Corylus avellana and Acer spp., which are not represented in our surveys.

Limestone rocky walls, from 1400 m up to the highest peak of Mt. Pozzoni, are colonized by a characteristic chasmophytic vegetation dominated by Saxifraga callosa (rel. 4–6) with the presence of Saxifraga paniculata, Campanula tanfanii and Saxifraga exarata subsp. ampullacea (cluster 3). Even if Trisetum villosum was not found within the relevès, this species is present in such habitats of the study area (see floristic list). The overall floristic composition of these coenoses allows us to refer them to Saxifrago australis-Trisetetum bertolonii (Saxifragion lingulatae, Potentilletalia caulescentis, Asplenietea trichomanis), a widespread association in the Umbria-Marche Apennine and Central Italy (Giancola and Stanisci 2002).

On sub-vertical calcareous rocky outcrops, large boulders and ledges, we found some peculiar communities characterized by the abundance and dominance of Sedum album. At higher altitudes, above 1650 m (rel. no. 7–9) these coenoses are characterized by Paronychia kapela, Anthemis cretica subsp. columnae, Sempervivum arachnoideum and Poa molinerii (cluster 8). The floristic composition is dominated by species belonging to Sedo albi-Scleranthetea biennis such as Sedum album, Sempervivum arachnoideum and Petrosedum rupestre together with several transgressive species from dry grasslands of Festuco-Brometea. These coenoses developed on a calcareous substrate have to be attributed to the alliance Alysso alyssoidis-Sedion albi. At the alliance level, the same attribution is valid for the relevès no.10–12 (cluster 6), carried out on large rocky ledges at lower altitudes (ca 1500 m) which are physiognomically characterized by the endemic Iris marsica and by Petrosedum rupestre, with the presence of several thermophilous species such as Crupina vulgaris, Lactuca perennis subsp. perennis and Centaurea deusta. The survey no. 13, characterized also by the presence of Iris marsica but with the dominance of Bromopsis erecta, represents the ecotone between the vegetation of the Alysso-Sedion on ledges and the contiguous dry grasslands of Festuco-Brometea, which are developed where the soils are more evolved and deeper. Our current state of knowledge about Alysso-Sedion vegetation in the studied area does not make it possible to find a clear reference to any already described association; therefore these two coenoses are provisionally indicated as Sedum album-Paronychia kapela community and Sedum album-Iris marsica community.

Calcareous screes and mobile debris have only small surfaces in the study area; they are represented by the relevè no. 14 (cluster 7), carried out at medium altitude (1480 m), on the scree fed by the characteristic rocky spike present on the right side of the St. Rufo valley, known as Peschio dell’Aquila. This plant community has sparse cover and is characterized by Rumex scutatus, Galium magellense and Scrophularia canina. The scree vegetation of the alpine and subalpine belt in the Central Apennine is quite well known, while at lower altitudes it has rarely been investigated (see Ciaschetti et al. 2020 and references therein). Also in this case, it was not possible to identify a reference at the association level for the Petrosedum rupestre-Rumex scutatus community of the study area. The presence of Galium magellense suggests a probable framework within the alliance Linario-Festucion dimorphae, describing Apennine glareicolous communities of calcareous screes, from the supratemperate to orotemperate thermotypes, even if most of the diagnostic species are lacking. The floristic impoverishment could be justified by the fact that in the study area the most important screes are located at rather low altitudes, at the lower ecological limit of Linario-Festucion dimorphae. In fact, at higher altitude we observed in this habitat also the presence of Drypis spinosa. Although the abundance of Petrosedum rupestre would seem to indicate an affinity with the association Linario purpureae-Petrosedetum rupestris recently described for several localities of the Abruzzo territory (Ciaschetti et al. 2020), the overall floristic composition of the community herein reported is rather different from the one described for Abruzzo and the diagnostic species are absent. In addition, this thermophilic association was referred to a different order and alliance (Scrophulario bicoloris-Helicrhysetalia italici Brullo, 1984, Linarion purpureae Brullo, 1984) within the class Thlaspietea rotundifolii.

In the lower part of the study area, at an altitude below 1200 m, small patches of regularly mowed grasslands are still present (cluster 4; rel. no. 15–17), developed on deep, partially terraced, well drained alluvial soil. They are species rich, with 54 species per plot on average. Floristically, the dominant species (Trifolium incarnatum, T. repens, T. pratense, Poa trivialis, Dactylis glomerata, Phleum nodosum, Cynosurus cristatus) are indicators of the class Molinio-Arrhenatheretea, accompanied by several nitrophilous and ruderal species such as Bromus hordeaceus and Dasypyrum villosum. The perennial meso and supratemperate Apennine grasslands, usually grazed and mowed once a year, which develop on mesotrophic soils with good water availability and rich in nutrients, have been commonly attributed to the Cynosurion cristati alliance, (see the Italian review of the alliance in Blasi et al. 2012 and references therein). The classification of Cynosurion grasslands has often been considered to be somewhat problematic (Blasi et al. 2012) due to the fact that exclusive species are lacking and most of the diagnostic species range widely from both a geographical and ecological point of view. Although the surveys carried out in the study area can be referred to Cerastio arvensis-Cynosurenion cristati sub-alliance, the attribution to an already described association remains unresolved, also because the Apennine’s associations have not yet been the subject of a critical review which clarifies delimitation and differential species. Probably the closest association could be identified in the Colchico lusitani-Cynosuretum, repeatedly reported on the Umbria-Marche Apennines (e.g. Allegrezza 2003; Biondi et al. 2004; Catorci et al. 2007).

The most widespread vegetation in the study area is represented by the dry grasslands of the Festuco-Brometea class (cluster 5; rel. no. 18–30), mainly used for horse and cattle grazing, which replaced the beech forest vegetation on the mountain slopes. In particular, they can be classified in Phleo ambigui-Brometalia order including xerophilous and semi-mesophilous secondary grasslands of the Central-southern Apennines, that occur from the supramediterranean to the upper supratemperate thermotype. These plant communities have a high physiognomic and floristic diversification in relation to local characteristics of the site (exposure, rockiness, soil depth and pH) and to the degree of grazing. The relevès no. 18–22 (cluster 10) are particularly species rich (mean 52 species per releve) and were found at lower altitude (max 1300 m), frequently on moraine deposits. They are characterized by a high incidence of chamaephytes (e.g. Helianthemum apenninum, H. oelandicum subsp. incanum, H. nummularium subsp. obscurum, Thymus longicaulis, T. oenipontanus) and by the presence of several therophytes (e.g. Trifolium campestre, T. scabrum, Euphrasia liburnica). However, they are physiognomically dominated by hemicryptophytes such as Bromopsis erecta, Festuca circummediterranea, Phleum hirsutum subsp. ambiguum. From a phytosociological point of view, the ecology and floristic analysis led to the inclusion of this community in the association Asperulo purpureae-Brometum erecti, frequently reported for the Umbria-Marche Apennine (e.g. Catorci et al. 2007) and described with several variants and subassociations. The releve no. 23 represents a particular stand on strongly inclined slopes at higher altitude (1500 m) dominated by Bromopsis erecta but with a high cover of Securigera varia and Petrosedum rupestre, which cannot be easily classified at the level of association.

At higher altitude (cluster 9) and on more inclined slopes, in the dry grasslands can be noted the presence of Sesleria nitida and a floristic composition close to the association Seslerio nitidae-Brometum erecti. Near the summit area of the mountain slopes or in eroding areas, the floristic composition becomes impoverished and the spiny chamaephyte Astragalus sempervirens was found as co-dominant with Sesleria nitida. The reference for this community is the Astragalo sempervirenti-Seslerietum nitidae, an association described for the grasslands of the summit sectors of Coscerno and Civitella Mountains in Umbria (Biondi and Ballelli 1995). The parts at higher altitudes of the mountain slopes, relying on calcareous-marly substrata, are occupied by grasslands dominated by Brachypodium genuense. The presence of some acidophilic species (e.g. Luzula campestris, Genista sagittalis, Campanula micrantha) which are frequently found in the vegetation of Nardetea strictae (see Di Pietro et al. 2017 for a review of these communities in the Italian Peninsula), indicates the presence of decarbonated soils with a lower pH. Despite this, the floristic composition is clearly dominated by Festuco-Brometea species; therefore, the reference for these coenoses, is the order Phleo ambigui-Brometalia erecti and the alliance Phleo-Bromion erecti, but unlike the previous ones, in this case the arid high-montane grasslands are to be referred to the sub-alliance Brachypodienion genuensis. At the association level, the floristic analysis led to referring this community to the Potentillo rigoanae-Brachypodietum genuensis, an association quite widespread in the Central Apennine, in particular in Lazio and Abruzzo regions (Lucchese et al. 1995).

We did not survey other relevant coenoses that are present with significant extensions but only outside the surveyed area: the mountain acidophilic grasslands of the Nardetea strictae class, present on the northern slopes of Mt. Pozzoni and in the concave morphologies in the high-mountain orotemperate belt and the discontinuous prairies of the steep slopes dominated by Sesleria juncifolia; the latter can be observed on the steep and inaccessible mountain slope surrounding the cliff of Peschio dell’Aquila.