PHYTOSOCIOLOGICAL ANALYSIS OF ALPINE SWARDS WITH DOMINANT SALIX SERPILLIFOLIA IN THE JULIAN ALPS ( NW SLOVENIA , NE ITALY )

Phytosociological analysis of alpine swards with dominant Salix serpillifolia in the Julian Alps (NW Slovenia, NE Italy) In the alpine belt of the Julian Alps (Mts. Kukova Špica, Triglav, Pihavec, Razor, Jalovec, Mangart and Lopa) we conducted a phytosociological analysis of swards on ledges, ridges and rock faces with dominant Salix serpillifolia. These sites are typically relatively moist and the snow cover there is usually very persistent, despite their location on or just below ridges. In terms of species composition the studied community is transitional between snow-bed communities of the order Arabidetalia caeruleae and communities of windward ridges from the alliance Oxytropido-Elynion that we classify into the class Elyno-Seslerietea. Based on the analysis of proportions of diagnostic species we classify the studied community into the alliance Oxytropido-Elynion and into the new eastern-Alpine association Gentiano pumilae-Salicetum serpillifoliae. In the article we also provide a slightly modified phytosociological table of another alpine community in the Julian Alps, Crepido terglouensis-Potentilletum nitidae.

Salix serpillifolia is an Alpine-Illyrian species, character species of alpine grasslands of windy ridges with naked rush from the class Carici rupestris-Kobresietea bellardii (Aeschimann et al. 2004a: 462).It occurs also in chasmophytic communities, communities of moist screes and snow beds.It is one of few woody plants that can grow also in the nival belt (Leuschner & Ellenberg 2017: 370).In Slovenia, this willow occurs on moist gravel and swards in the (altimontane), subalpine and alpine belts in the Julian Alps, the Karavanke Mts., the Kamnik-Savinja Alps and on the Trnovski Gozd Plateau (Figure 1).The lowest it has been reported from until now was in two deep sinkholes under Mt.Veliki Golak on the Trnovski Gozd Plateau: in Kraljeva Kamra to the east of the mountain at 1,295 m a.s.l. and in a sinkhole to the north of the mountain, at 1,350 m a.s.l.(leg.& det.I. Dakskobler, 18. 7. 2001, herbarium LJS), and the highest under the peak of Mt.Škrlatica, at 2,750 m a.s.l.(det.I. Dakskobler, 19. 8. 2009).It occurs also in the stands of the following associations: Caricetum ferrugineae s.In our previous research into alpine vegetation we did not discuss in more detail the swards with dominant Salix serpyllfolia that we found on slightly moist sites on ridges or immediately under them on several high summits in the Julian Alps.Other authors (Grabherr & Mucina 1993, Englisch 1999, E. Pignatti & S. Pignatti 2014, 2016) do not report similar communities in other parts of the Southern, Southeastern and Eastern Alps.Only in Englisch et al. (1993: 315) there is a note on a Salix serpillifolia community, which belongs to Seslerietalia albicantis, and in Englisch (1999: 179) a note on a Salix serpillifolia form of the association Crepidetum terglouensis Seibert 1977.We therefore collected our relevés and classified them into a syntaxonomic system based on the phytosociological analysis.

METHODS
Alpine communities with dominant Salix serpillifolia in the Julian Alps were studied applying the Braun-Blanquet method (Braun-Blanquet 1964).In the FloVegSi database (Fauna, Flora, Vegetation and Paleovegetation of Slovenia) of the Jovan Hadži Institute of Biology at ZRC SAZU (T.Seliškar, Vreš et A. Seliškar 2003) we found a total of 26 relevés of subalpine and alpine swards where Salix serpillifolia was one of dominant species.They were arranged into a working table based on hierarchical classification.We transformed the combined cover-abundance values with numerical values (1-9) according to van der Maarel (1979).Numerical comparisons were performed with the SYN-TAX 2000 program package (Podani 2001).The relevés were compared by means of (unweighted) average linkage method -UPGMA, using Wishart's similarity ratio.
In the first step we found a homogenous group of 13 relevés with dominant Salix serpillifolia, which were made in the alpine belt of the Julian Alps.In Tone Wraber's manuscript collection kept by the Botanical Garden of the University of Ljubljana we found only four relevés of alpine swards from the Mangart ridge with dominant Salix serpillifolia and compared them with our selected relevés.Due to their obvious similarity they were incorporated into the phytosociological table which we subsequently arranged and analysed by groups of diagnostic species.
The nomenclature source for the names of vascular plants is the Mala flora Slovenia (MFS - Martinčič et al. 2007).The nomenclature of Flora alpina -Sesleria caerulea was used for the taxon Sesleria caerulea subsp.calcaria (MFS) and the nomenclature of Vascu-lar flora of Friuli Venezia Giulia (Poldini, Oriolo et Vidali 2002) for the taxon Achillea clavennae.We used the name Salix serpillifolia (the nomenclature of MFS and Flora alpina) instead of the name Salix serpyllifolia (Trpin & Vreš 1995: 80, Dakskobler & Zupan 2017).Ros et al. (2013) are the nomenclature source for the names of mosses and Suppan et al. (2000) for the names of lichens.Prof. Andrej Martinčič determined the collected mosses.For the names of syntaxa we follow Grabherr & Mucina (1993), Oriolo (2001), Theurillat (2004), Šilc & Čarni (2012), E. Pignatti & S. Pignatti (2014) and Mucina et al. (2016).In the classification of species into phytosociological groups (groups of diagnostic species) we mainly refer to the Flora alpina (Aeschimann et al. 2004a, b).The geographic coordinates of relevés are determined according to the Slovenian geographic coordinate system D 48 (5th zone) on the Bessel ellipsoid and with Gauss-Krüger projection.
All of the relevés discussed in this article were made in the Julian Alps.The geological bedrock is mainly calcareous, limestone, dolomite limestone, sporadically interlayered with more silicate rocks, marlstone, claystone and chert (Buser 2009).The studied community occurs on initial soils (lithosols) and shallow rendzinas on limestone and dolomite (Lovrenčak 1998, Vidic et al. 2015).The climate is montane, with mean annual precipitation of 2,500 mm to 3,000 mm (Zupančič 1998) and mean annual air temperature of -2 ºC to 0 ºC (Cegnar 1998).The studied community is associated with specific sites which have usually longer average periods of snow cover than the surrounding sites.Elyno-Seslerietea Br.-Bl. 1948Seslerietalia coeruleae Br.-Bl. in Br.-Bl. et Jenny 1926Oxytropido-Elynion myosuroidis Br.-Bl. 1950 Gentiano pumilae-Salicetum serpillifoliae T. Wraber ex Dakskobler ass.nov.hoc loco, the nomenclature type, holotypus, is relevé 8 in Table 2. Justification: Tone Wraber was the first to find alpine stands with dominant Salix serpillifolia under Mt.Mangart and made four relevés.One of them is also the nomenclature type of the new association.Although he cannot be considered co-author of this paper due to his passing eight years ago, I attribute to him the first authorship of the association validly described below (Weber, Moravec & Theurillat 2000, Recommendation 46D).

Alpine stands with dominant Salix serpillifolia in the Julian Alps
We extracted our relevés of subalpine-alpine communities with dominant Salix serpillifolia from FloVegSi database and compared them by means of hierarchical classification (Figure 2).The results show that some of the relevés are floristically different, including the relevé of a moist scree in the hollow of Matajurc under the summit of Matajurski Vrh in the Southern Julian Alps (Table 1), which we classify into the provisionally described association Ranuculo traunfellneri-Salicetum serpillifioliae nom.prov.In terms of site conditions (a gravelly depression with persistent snow cover) and dominant species (Salix serpillifolia, Ranunculus traunfellneri, Galium noricum, Moehringia ciliata and Salix waldsteiniana) it belongs to the alliance Arabidion caeruleae and class Thlaspietea rotundifolii.However, a reliable syntaxonomic classification of this relevé will only be possible when we have found more similar stands.Englisch (1999: Table B) mentions a slightly similar community (Salix serpillifolia-Ranunculus alpestris community) for the Northeastern Alps, but it is also documented with only two relevés.Other different relevés belong to the syntaxa that have already been reported in the Julian Alps: Seslerio sphaerocpehalae-Dryadetum octopetalae (Dakskobler & Surina 2017a), Homogyno discoloris-Salicetum retusae (Surina 2005), Caricetum ferrugineae s. lat.(Surina 2005) and Salici retusae-Geranietum argentei salicetosum serpillifoliae (Surina 2005, Dakskobler 2011).A relatively homogeneous group of 13 relevés cannot be classified into any of so far described associations.Salix serpillifolia dominates in all these relevés which were made exclusively in the alpine belt.After we had conducted the first analysis we found four similar relevés from the Mangart ridge in Tone Wraber's manuscripts (he made at least one of them on the Italian side of the mountain), also with dominant Salix serpillifolia.We entered these four relevés into the FloVegSi database and compared them with the other 13 relevés (Figure 3).Tone Wraber's Mangart relevés grouped with ours, indicating that we both inventoried the same community, although 20 years apart (his relevés are from1983; his companion and assistant in the field was Andrej Podobnik).As no similar stands with dominant Salix serpillifolia in the alpine belt on calcareous bedrock have been reported elsewhere in the Alps, we joined our 13 with Wraber's four relevés in Table 2 and described them as the new association Gentiano pumilae-Salicetum serpillifoliae.This association comprises alpine or cushion-like swards at elevations ranging from 2,350 to 2,650 m, on small ridge plateaus as well as on steep, slightly gullied and shady lee slopes just under summits, on sites with longer periods of snow cover than their surroundings.Such swards develop on very limited areas, measuring not more than 10 m 2 (Lopa, Jalovec, Razor, Plemenice and Zaplanja under Triglav), rarely (Pihavec, Mangart, Kukova Špica) on larger areas measuring up to 20 m 2 .Figure 4 shows the current distribution of stands of the new association.

RESULTS AND DISCUSSION
The diagnostic species of the new association include, in addition to the dominant willow Salix serpillifolia, also Carex capillaris, Gentiana pumila, Doronicum glaciale and Saxifraga paniculata.The first three in particular are characteristic for slightly moist to wet sites, moist alpine swards, snow beds and headwaters.Salix serpillifolia and Saxifraga paniculata are indicative also of ridge positions and the contact with alpine chasmophytic communities.Gentiana pumila is an eastern-Alpine species, a character species of the alliance Caricion ferrugineae (Aeschimann et al. 2004b: 20) that charac-terises the new association both in terms of ecology and chorology as an endemic community of the Eastern Alps.Its distribution area is significantly smaller than the distribution area of Salix serpillifolia.Composition by the groups of diagnostic species (Table 3) shows a higher proportion of species of subalpine-alpine grasslands (Oxytropido-Elynion, Caricion firmae, Caricion ferrugineae, Seslerietalia coeruleae, Elyno-Seslerietea) than of scree species (Arabidetalia caeruleae, Thlaspietea rotundifolii).In previous articles (Dakskobler & Surina 2017a, Dakskobler & Zupan 2017) we classified Salix serpillifolia as a diagnostic species of snow-bed communities (Arabidetalia caeruleae).Phytosociologists (Grabherr 1993, Theurillat in Aeschimmann 2004a) consider it a diagnostic species of the class Carici rupestris-Kobresietea bellardii.It is our opinion that alpine communities of windward ridges in the Slovenian Alps belong to the special alliance Oxytropido-Elynion, but not to a special class Carici rupestris-Kobresietea bellardii (Oriolo 2001, Dakskobler & Surina 2017a).If we take into account the dominant species it could be classified into this alliance based on the analysis of diagnostic species, but the new association could also be classified into the alliance Caricion firmae or even into the alliance Arabidion caeruleae.We therefore described a special type of alpine vegetation with species characteristic for three groups of communities (snow beds, swards and windward ridges).In the Julian Alps we recently described another slightly similar community, association Saxifrago paniculatae-Caricetum fuliginosae (Dakskobler & Surina 2017a, Table 6).Two diagnostic species occur in both associations (Salix serpillifolia and Saxifraga paniculata).As many as 31 of 35 species recorded in the stands of this association occur also in the stands of the association Gentiano pumilae-Salicetum serpillifoliae, but floristic similarity between both compared syntaxa is only 45% (Sørensen 1948).The stands of the other association are much more species-rich (on average 24 species per relevé compared to an average of 12 species per relevé in the stands of the first association); they can cover slightly larger areas and more distinctly resemble alpine swards.Another decisive factor is the difference in the coverage of both dominant species (Carex fuliginosa / Salix serpillifolia) and in site ecology.The soil in the stands of the second association is more developed, in places rendzina.Nevertheless, these are two relatively similar and rare forms of alpine vegetation in the Julian Alps.

Corrected phytosociological table of the association Crepido terglouensis-Potentilletum nitidae (Dakskobler & Zupan 2017)
During the review of the herbarium material collected in the summer of 2016 we observed that a cushion-forming plant that we recorded in several stands of the association Crepido terglouensis-Potentilletum nitidae on a plateau west of Mt.Triglav had been misdetermined.Two species were reported in field notes, Minuartia cherlerioides and Arenaria ciliata, but in our review of the herbarium material we could only find Arenaria ciliata.Consequently, we have to revise the diagnostic species of this association.They are Potentilla nitida, Crepis terglouensis, Eritrichium nanum, Alyssum ovirense and Arenaria ciliata (but not Minuartia cherlerioides).Below we provide a slightly modified phytosociological table (Table 4) without Minuartia cherlerioides (for which we have no supporting herbarium material) and a slightly different (irrelevant in terms of the syntaxonomic classification of the association) composition by groups of diagnostic species (Table 5).Everything else that has so far been reported for this association remains unchanged, including the dendrogram in Figure 4 (Dakskobler & Zupan, ibid.).Despite misdetermination of one of the diagnostic species the description of the new association Crepido terglouensis-Potentilletum nitidae Dakskobler et Zupan 2017 does not require a formal correction (Article 43 -Correction of names due to taxonomic errors), because our error does not pertain to the species that gives the association its name (Weber, Moravec et Theurillat 2000).

CONCLUSIONS
The alpine community with dominant Salix serpillifolia was first reported on the Mangart ridge by Tone Wraber (1983, manuscript collection kept by the Botanical Garden of the University of Ljubljana), who made four relevés at the time, but never published anything on the subject.We described a similar community under Mt.Lopa in the Kanin Mts., under Mt.Jalovec, on Mt.Pihavec, under Mt.Razor, on Plamenice and Zaplanja under Mt.Triglav and on Mt.Kukova Špica.Despite several differences between our relevés and Wraber's we had obviously studied the same community populating smaller or larger ridge plateaus or slightly gullied shady slopes with long snow cover.In addition to thyme-leaved willow the species that best characterise the new community include Carex capillaris, Doronicum glaciale, Gentina pumila and Saxifraga paniculata.Similar willow communities have not been reported elsewhere in the Southern and Eastern Alps, so we classified our stands into the new association Gentiano pumilae-Salicetum serpillifoliae.Presently, its stands remain specific for some of the highest summits of the Julian Alps, similarly to the stands of the association Saxifrago paniculatae-Caricetum fuliginosae, which are slightly similar in terms of species composition.So far, they have not been subject to significant human impact, although some of them are situated in the vicinity of well-frequented mountain paths (to Mt.Mangart and Mt.Jalovec).Potentially, they could be endangered by small cattle grazing.The species composition of the new community includes several species that are relatively rare in Slovenia, such as Erigeron uniflorus, Antennaria carpatica, Gentiana orbicularis, Luzula spicata, Juncus jacquinii, Sesleria ovata, Omalotheca supina (Gnaphalium supinum), Sib-baldia procumbens, Soldanella pusilla, red-listed Elyna myosuroides (Anon.2002), protected Nigritella miniata s. lat.(N.rubra s. lat., N. hygrophila) and Primula au-ricula (Anon.2004), and southeastern-Alpine endemic species Cerastium subtriflorum, Saxifraga tenella and Saxifarga exarata subsp.carniolica.
FOLIA BIOLOGICA ET GEOLOGICA 59/1 -2018 I would like to thank the heirs of the late Prof.Dr. Tone Wraber for giving his manuscripts and professional literature to the safekeeping of the Botanical Garden of the University of Ljubljana, and to its director, Dr. Jože Bavcon, who allowed us to examine professor's legacy.