544 Vizintin et al.vp CODEN: ABCRA 25 ISSN 0365–0588 eISSN 1847-8476 Floristic analysis of a high-speed railway embankment in a Mediterranean landscape GOFFREDO FILIBECK1*, PAOLO CORNELINI2**, PAOLO PETRELLA3 1 Department of Agriculture, Forests, Nature and Energy, University of Tuscia, I-01100 Viterbo, Italy 2 Istituto Sperimentale Ferrovie dello Stato, Roma, Italy 3 Via Tuscolana 909, I-00174 Roma, Italy Abstract – We analyzed the floristic composition of a 4.5 km-long segment of a high- -speed railway in Lazio, central Italy, which travels on an artificial embankment through an intensively-farmed landscape. In total, 287 vascular plant species were recorded. The life-form distribution was found to be similar to that of the regional species pool, with high percentages of therophytes (38%) and phanerophytes (13%). In the chorological spectrum the Mediterranean floristic element prevailed (44%), while alien species were 8% of the flora. The phytosociological spectrum showed a high diversity of characteristic species from the class Stellarietea mediae or its subordinate syntaxa (26%), and in particular from the order Thero-Brometalia (Mediterranean, sub-nitrophilous annual communities). Species from forest syntaxa had a relatively high diversity (9%). These results suggest that the ecological filtering provided by the Mediterranean regional climate controlled species assemblage even in a completely artificial habitat, preventing floristic homogenization: the flora of the studied railway section is only partially »ruderalized«, while it keeps strong links with the regional (semi-) natural plant communities. However, in contrast to what is observed in central and north Europe, the railway sides studied in the present paper do not seem to represent a refugial habitat for rare species from grassland communities, mainly because in Italy semi-natural dry grasslands are still widely represented. Key words: anthropogenic, habitat, artificial soil, life-form, railway flora, Lazio, Italy Introduction Railways and railway verges are colonized by a high number of plant species, and have been the subject of botanical studies for more than 150 years (see references in: MÜHLENBACH ACTA BOT. CROAT. 71 (2), 2012 229 * Corresponding author, e-mail: filibeck@unitus.it ** Present address: Via Scandriglia 7, I-00199 Roma, Italy Copyright® 2012 by Acta Botanica Croatica, the Faculty of Science, University of Zagreb. All rights reserved. Acta Bot. Croat. 71 (2), 229–248, 2012 1979; BRANDES 1983, 1993, 2008; CORNELINI and PETRELLA 1996; SCHOENENBERGER et al. 2002; NOWI�SKA and CZARNA 2008). Some works have focused on the negative role of rail lines as dispersal pathways for alien species (SCHOENENBERGER et al. 2002, CHRISTEN and MATLACK 2006, RANTA 2008, TRET’YAKOVA 2010) – although due to the decrease in grain and livestock rail transportation in the last few decades, railways have nowadays a less rich alien flora than observed in the first half of the 20th century (BRANDES 1983: 38, CORNELINI and PETRELLA 1996, TINNER and SCHUMACHER 2004). On the other hand, several central and north European studies have underlined the role of road and railway verges and embankments in hosting a surprisingly high percentage of a country’s native floristic diversity, and have showed that they can even act as habitats for rare or endangered species (e.g. SARGENT 1984, BRANDES 1993, TIKKA et al. 2000, SCHAFFERS and SYKORA 2002, WITTIG 2002, TINNER and SCHUMACHER 2004, RANTA 2008). A floristic survey of the Dutch railway network found a total of 1,026 species, i.e. 63% of the country’s flora (KOSTER 1987), while in Britain a total of 1,632 vascular plant species and subspecies was recorded from railway land (SARGENT 1984). In Finland, 4% of the nationally endangered species regularly occur on road and rail verges (TIKKA et al. 2000). In natural landscapes, roads and railways mainly function as a source of fragmentation for habitats and populations (CHRISTEN and MATLACK 2006, FISCHER and LINDENMAYER 2007). In highly transformed landscapes, on the other hand, rail and road sides – being a relatively undisturbed habitat compared to the surrounding areas (MESSENGER 1968, BRANDES 1993) – may act as corridors for the survival and dispersal of plant populations from endangered natural or semi-natural communities (TIKKA et al. 2001, RANTA 2008), especially if the railway verges are managed according to biodiversity-oriented criteria (PARR and WAY 1988; CORNELINI et al. 1990; CORNELINI 1994a, b; TIKKA et al. 2000, 2001). However, in Italy (and, to our knowledge, in most of Mediterranean Europe) botanical studies on rail lines are much scarcer than in central European countries (cf. BRANDES 1993: 441) and are focused on railway stations only (CACCIATO 1952; CORNELINI and PETRELLA 1996, 1997) or on the classification of plant communities (BRANDES 1992; CORNELINI 1994a, b). In this study, we present the results of a complete floristic survey of a 4.5 km segment of a high-speed railway (i.e. a passenger rail transport system that operates above 200 km h–1), across an intensively farmed landscape within the Mediterranean region of Central Italy. The rail line segment was built in 1975; the floristic survey took place in 1993, within a project carried out by one of the authors (P. C.) at the Research Institute of Italian State Railways, aimed at monitoring the plant-cover evolution of rail embankments without hydroseeding or other revegetation practices. The results of the floristic survey remained unpublished. We believe they are nowadays of interest, for many reasons. First, no other complete floristic studies have been performed, to our knowledge, on a long segment of an Italian railway line beyond railway stations and urban areas; second, it is now very difficult to obtain permission from the railway authorities to perform botanical studies on high-speed lines, because of increased operational speeds and the stricter security policy; finally, recently enforced maintenance procedures now include much more frequent mowing of embankments than at the time of our survey, so that the data collected under a lower disturbance regime can be useful for further studies comparing the effects of different management practices. 230 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Materials and methods The surveyed railway segment is 4.5 km long and belongs to the high-speed Florence- -Rome line. This line was the first high-speed railway opened in Europe (it started operating in 1977). The studied section is located in the Municipality of Rome (Lazio, central Italy), and travels on an uninterrupted embankment, i.e. a raised earth and gravel structure (with the exception of a bridge over the river Tiber), thus providing with its sides a large surface of a man-made substrate, raising above the cultivated land. The embankment begins at the end of a viaduct near Settebagni (at the 18 km milepost), and ends at the 22,5 milepost (where a series of tunnels begins). It was built in 1975 and is made up of a mixture of coarse-grained soil and crushed rock that was compacted during the construction work so as to ensure mechanical resistance and low permeability. In contrast to the current usual practice in analogous earthworks, the slopes of the embankment were not sown with stabilizing grass mixtures during or after construction, so the colonizing process was completely spontaneous. Ever since the line came into operation, herbicide spraying has been done on the track ballast only; the embankment slopes, at the time of the field study, were left mostly undisturbed. The dominant vegetation types on the embankment slopes and sides included: annual Mediterranean grasslands, patches of perennial grasslands, hygrophilous herbaceous com- munities (along the drainage ditches), stands of shrubs (mostly dominated by Spartium junceum) (cf. CORNELINI 1994b). The rail segment travels in the Tiber plain, at approx. 20 m a.s.l., with a N-S orientation; the railway is more or less parallel to the riverbed, although due to the many meanders the distance between the rail line and the river banks varies between ca. 100–1000 m (except where the railway crosses the river). The plain is ca 3 km wide and is surrounded by a series of pyroclastic hills (max. altitude 150 m). The climate is Mediterranean; namely, the area belongs to the meso-Mediterranean, sub-humid belt, i.e. a climate type with an annual rainfall of approx. 800–900 mm, a marked summer drought from June to August and mild winter temperatures (BLASI 1994). Much of the floodplain surrounding the rail segment is intensively farmed: hedgerows and other residual habitats for wild plants are scarce. The river banks host poorly-preserved fragments of riparian vegetation, dominated by Populus sp.pl. and Salix sp. pl. The heavily- -trafficked Milan-Rome motorway, too, travels in the floodplain parallel to the rail line, at a distance of a few hundred meters. The hill-slopes feature deciduous, xerophilous coppices dominated by Quercus cerris (Teucrio siculi-Quercion cerridis alliance) (BLASI et al. 2010, FILIBECK and SCOPPOLA 2011). The floristic survey was done in 1993. The whole length of the segment of the railway was walked, on both sides of the embankment, in both directions. The walk was repeated in different seasons. All vascular plant species observed on the embankment slopes, including the drainage ditches at the base, were recorded. The survey area defined in this way was ca 20 m wide on each side of the rail line. The surveyed area did not include the ballast, because on high-speed lines the permanent way is kept free of vascular plants through frequent herbicide spraying. The plant list of the first 1,000 m was recorded separately, in order to compare the species richness of a 1-km segment with that of the whole 4.5 km stretch. It was not possible (due to the inherent safety problems of working on a high-speed line) to divide the study site into statistically formalized sampling units (plots or transects) in order to obtain ACTA BOT. CROAT. 71 (2), 2012 231 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT quantitative data on species abundance. However, 12 phytosociological relevés were done on the embankment slopes at the beginning of the field study (and published as a synoptic table in CORNELINI 1994b). No significant differences were observed, during the phytosocio- logical survey between the east- and west-facing slopes of the embankment: therefore, during the subsequent floristic survey no separate floristic lists were recorded for the two sides. Identification of species and nomenclature followed PIGNATTI (1982). Each species was then assigned a life-form type and a geographic element according to PIGNATTI (1982), in order to analyze the relationships with the regional species-pool. The subdivision of floristic zones and regions, and thus of geographic elements, used by PIGNATTI (1982), stresses some patterns relevant for the Italian peninsula (e.g. a distinction between »steno-Mediterranean« and »euri-Mediterranean« species is adopted) – thus it does not match the other systems used in central Europe perfectly. A species was defined as »alien« if included in the check-list of Italian alien taxa by CELESTI-GRAPOW et al. (2010), and its status (casual, naturalized or invasive) was taken from the same source. Alien »species« defined in this way include also taxa originating in cultivation. Finally, each species was assigned to a phytosociological unit, in order to analyze the relationships between the floristic assemblage of the railway sides and the (semi-)natural vegetation types of the surrounding landscape. In order to do so in a standardized and repeatable way, this was done assigning to each phytosociological class or order only those plants that are considered »characteristic species« of that unit, following reference manuals (OBERDORFER 1992, MUCINA et al. 1993) and syntaxonomical revisions (IZCO 1977, BIONDI et al. 1995, BLASI et al. 2004, GIGANTE and VENANZONI 2007). Results A total of 287 vascular plant species was recorded in the research area (Tab.1); 207 species (72%) were found within the first 1,000 m. The richest family was found to be Asteraceae (16.4%), followed by Fabaceae and Poaceae (ca. 12%). The life-form types with the highest diversity were therophytes and hemicryptophytes – accounting for 38% each (Fig. 1). As for hemicryptophytes, many of the species found in the 232 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Fig. 1. Life-form distribution in the flora of the railway segment. For abbreviations see table 1. ACTA BOT. CROAT. 71 (2), 2012 233 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Tab. 1. List of recorded species. Legend of abbreviations – Life forms: Ch – chamaephytes, G – geo- phytes, H – hemicryptophytes, H(b) – biennial hemicryptophytes, I – hydrophytes, P – phanerophytes, T – therophytes. Geographic elements: »Circumboreal« includes also the Euro-Siberian element; »Cosmopolitan« includes also the Sub-Cosmopolitan element; »Eu- rasiatic« includes also the European element. Origin of aliens: Afr – Africa, Eur – Europe, hort. – horticultural (taxa originated in cultivation), N Amer – North America, S Amer – South or Central America. Status of aliens in Lazio: cas – casual, inv – invasive, nat – naturalized. Vegetation units: Av – Artemisietea vulgaris, C-M – Cisto-Micromerietea, F-B – Festuco-Brometea, G-U – Galio-Urticetea, Hg – Helianthemetea guttati, hy – riparian and hygrophilous communities, M-A – Molinio-Arrhenateretea, Qi – Quercetea ilicis, Q-F – Querco-Fagetea, R-P – Rhamno-Prunetea, St – Stellarietea mediae (except Thero-Brome- talia),T-Brom – Thero-Brometalia, T-G – Trifolio-Geranietea. Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Acer negundo L. P Alien N Amer cas Agrimonia eupatoria L. H Cosmopolitan T-G Agropyron repens (L.) Beauv. G Circumboreal Av Ailanthus altissima (Miller) Swingle P Alien Asia inv Alcea setosa (Boiss.) Alef. H Alien Eur nat Alisma plantago-aquatica L. I Cosmopolitan hy Allium ampeloprasum L. G Euri-Mediterranean Alopecurus myosuroides Hudson T Cosmopolitan St Althaea cannabina L. H Eurasiatic Amaranthus retroflexus L. T Alien N Amer inv Anagallis arvensis L. T Euri-Mediterranean St Anchusa hybrida Ten. H Steno-Mediterranean Anchusa italica Retz. H Euri-Mediterranean Andryala integrifolia L. T Euri-Mediterranean St Anthemis arvensis L. T Steno-Mediterranean St Anthemis tinctoria L. H(b) Eurasiatic Av Apium nodiflorum (L.) Lag. H Euri-Mediterranean hy Arenaria serpyllifolia L. T Cosmopolitan Hg Artemisia verlotorum Lamotte H Alien Asia inv Artemisia vulgaris L. H Circumboreal Av Arum italicum Miller G Steno-Mediterranean G-U Arundo donax L. G Alien Asia inv Asparagus acutifolius L. P Steno-Mediterranean Qi Astragalus hamosus L. T Medit.-Turanic T-Brom Avena barbata Potter T Euri-Mediterranean T-Brom Avena fatua L. T Eurasiatic St Avena sterilis L. T Euri-Mediterranean T-Brom Bellevalia romana (L.) Sweet G Euri-Mediterranean Bellis perennis L. H Eurasiatic M-A Beta vulgaris L. cv. H Alien hort. cas Blackstonia perfoliata (L.) Hudson T Euri-Mediterranean Hg Borago officinalis L. T Euri-Mediterranean Briza maxima L. T Subtropical Hg 234 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Bromus gussonei Parl. T Euri-Mediterranean St Bromus hordeaceus L. T Cosmopolitan T-Brom Bromus madritensis L. T Euri-Mediterranean T-Brom Bromus rigidus Roth T Subtropical T-Brom Broussonetia papyrifera (L.) Vent. P Alien Asia inv Calamintha nepeta (L.) Savi H Montane-Mediterranean Calendula arvensis L. T Euri-Mediterranean St Calystegia sepium (L.) R.Br. H Eurasiatic G-U Campanula rapunculus L. H(b) Eurasiatic Capsella bursa pastoris (L.) H(b) Cosmopolitan St Cardamine hirsuta L. T Cosmopolitan Cardaria draba (L.) Desv. G Medit.-Turanic Carduus nutans L. H(b) Atlantic Carduus pycnocephalus L. H(b) Medit.-Turanic St Carex caryophyllea La Tourr. H Eurasiatic F-B Carex divisa Hudson G Atlantic Carex divulsa Stokes H Euri-Mediterranean Carex flacca Schreber G Eurasiatic Carex otrubae Podp. H Atlantic hy Carlina corymbosa L. H Steno-Mediterranean Hg Celtis australis L. P Euri-Mediterranean Centaurea solstitialis L. H(b) Steno-Mediterranean Av Centaurium erythraea Rafn H(b) Eurasiatic F-B Cephalaria transsylvanica (L.) Schrader T Eurasiatic Cerastium glomeratum Thuill. T Euri-Mediterranean St Cercis siliquastrum L. P Eurasiatic Q-F Chenopodium album L. T Cosmopolitan St Chondrilla juncea L. H Eurasiatic Chrozophora tinctoria (L.) Juss. T Medit.-Turanic Cichorium intybus L. H Eurasiatic Cirsium arvense (L.) Scop. G Eurasiatic St Cirsium vulgare (Savi) Ten. H(b) Eurasiatic Av Clematis vitalba L. P Eurasiatic Q-F Coleostephus myconis (L.) Cass. T Steno-Mediterranean Convolvulus arvensis L. G Eurasiatic Av Convolvulus cantabrica L. H Euri-Mediterranean Hg Conyza bonariensis (L.) Cronq. T Alien S Amer inv Conyza canadensis (L.) Cronq. T Alien N Amer inv Cornus sanguinea L. P Eurasiatic R-P Crataegus monogyna Jacq. P Eurasiatic R-P Crepis bursifolia L. H Endem. Crepis neglecta L. T Euri-Mediterranean Hg Crepis sancta (L.) Babc. T Medit.-Turanic St Tab. 1. – continued ACTA BOT. CROAT. 71 (2), 2012 235 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Crepis vesicaria L. T Atlantic St Cruciata laevipes Opiz H Eurasiatic G-U Cyclamen hederifolium Aiton G Steno-Mediterranean Q-F Cynara cardunculus L. H Steno-Mediterranean Cynodon dactylon (L.) Pers. G Cosmopolitan Cyperus longus L. G Eurasiatic hy Cyperus rotundus L. G Cosmopolitan hy Dactylis glomerata L. H Eurasiatic M-A Dasypirum villosum (L.) Borbas T Medit.-Turanic T-Brom Daucus carota L. H(b) Eurasiatic Av Diplotaxis tenuifolia (L.) Dc. H Atlantic Dipsacus fullonum L. H(b) Euri-Mediterranean Av Dorycnium hirsutum (L.) Ser. Ch Euri-Mediterranean Ecballium elaterium (L.) A.Rich. G Euri-Mediterranean St Echium italicum L. H(b) Euri-Mediterranean Av Echium plantagineum L. T Euri-Mediterranean T-Brom Echium vulgare L. H(b) Eurasiatic F-B Epilobium hirsutum L. H Eurasiatic Epilobium tetragonum L. H Eurasiatic Equisetum arvense L. G Circumboreal hy Equisetum ramosissimum Desf. G Circumboreal hy Erodium malacoides (L.) L’Her. T Steno-Mediterranean St Eryngium campestre L. H Euri-Mediterranean F-B Euonymus europaeus L. P Eurasiatic R-P Eupatorium cannabinum L. H Eurasiatic hy Euphorbia falcata L. T Euri-Mediterranean Hg Euphorbia helioscopia L. T Cosmopolitan St Euphorbia platyphyllos L. T Euri-Mediterranean Euphorbia prostrata Aiton T Alien S Amer inv Euphorbia segetalis L. T Steno-Mediterranean Fallopia dumetorum (L.) Holub T Circumboreal Ferula communis L. H Euri-Mediterranean Festuca arundinacea Schreber H Eurasiatic Ficus carica L. P Medit.-Turanic Foeniculum vulgare Miller H Euri-Mediterranean T-Brom Fraxinus ornus L. P Eurasiatic Q-F Fraxinus oxycarpa Bieb. P Eurasiatic hy Fumaria capreolata L. T Euri-Mediterranean St Fumaria officinalis L. T Eurasiatic St Galactites tomentosa Moench H(b) Steno-Mediterranean T-Brom Galega officinalis L. H Eurasiatic G-U Galium album Miller H Eurasiatic F-B Galium aparine L. T Eurasiatic G-U Tab. 1. – continued 236 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Gastridium ventricosum (Gouan) Sch. et Th. T Atlantic T-Brom Geranium dissectum L. T Eurasiatic St Geranium molle L. T Eurasiatic St Geranium robertianum L. T Cosmopolitan St Hedera helix L. P Euri-Mediterranean Q-F Hedysarum coronarium L. H Steno-Mediterranean Heliotropium europaeum L. T Euri-Mediterranean St Holcus lanatus L. H Circumboreal M-A Hypericum perforatum L. H Eurasiatic T-G Hypochoeris achyrophorus L. T Steno-Mediterranean Hg Hypochoeris glabra L. T Euri-Mediterranean Hypochoeris radicata L. H Eurasiatic F-B Inula conyza DC. H(b) Eurasiatic T-G Inula viscosa (L.) Aiton H Euri-Mediterranean Iris germanica L. G Alien hort. nat Juglans regia L. P Alien Asia cas Knautia integrifolia (L.) Bertol. T Euri-Mediterranean St Lactuca serriola L. H(b) Eurasiatic Lathyrus clymenum L. T Steno-Mediterranean St Lathyrus pratensis L. H Eurasiatic M-A Lathyrus sylvestris L. H Eurasiatic T-G Laurus nobilis L. P Steno-Mediterranean Qi Lavatera punctata All. T Steno-Mediterranean Lemna minor L. I Cosmopolitan hy Linaria vulgaris Miller H Eurasiatic Av Linum bienne Miller H(b) Euri-Mediterranean F-B Lophochloa cristata (L.) Hyl. T Cosmopolitan Lotus corniculatus L. H Eurasiatic T-G Lotus ornithopodioides L. T Steno-Mediterranean T-Brom Lycopus europaeus L. H Eurasiatic hy Malus domestica Borkh. P Alien hort. cas Malus sylvestris Miller P Eurasiatic Q-F Malva sylvestris L. H Circumboreal Av Medicago lupulina L. T Eurasiatic St Medicago orbicularis (L.) Bartal. T Euri-Mediterranean T-Brom Medicago sativa L. H Eurasiatic St Melica ciliata L. H Euri-Mediterranean F-B Melilotus alba Medicus T Eurasiatic Melilotus indica (L.) All. T Medit.-Turanic Melilotus officinalis (L.) Pallas H(b) Eurasiatic Melissa romana Miller H Steno-Mediterranean Mentha suaveolens Ehrh. H Euri-Mediterranean Mercurialis annua L. T Eurasiatic St Tab. 1. – continued ACTA BOT. CROAT. 71 (2), 2012 237 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Micromeria graeca (L.) Bentham Ch Steno-Mediterranean C-M Myosotis arvensis (L.) Hill T Eurasiatic St Narcissus tazetta L. G Steno-Mediterranean Nigella damascena L. T Euri-Mediterranean Hg Odontites rubra (Baumg.) Opiz T Eurasiatic Onobrychis viciifolia Scop. H Montane-Mediterranean F-B Ononis spinosa L. Ch Euri-Mediterranean F-B Onopordum illyricum L. H(b) Steno-Mediterranean Av Ophrys apifera Hudson G Euri-Mediterranean F-B Origanum vulgare L. H Eurasiatic T-G Ornithogalum umbellatum L. G Euri-Mediterranean St Oryzopsis miliacea (L.) Asch. et Schweinf. H Steno-Mediterranean Oxalis corniculata L. H Euri-Mediterranean Oxalis dillenii Jacq. H Alien N Amer inv Pallenis spinosa (L.) Cass. T Euri-Mediterranean Papaver dubium L. T Medit.-Turanic Papaver rhoeas L. T Medit.-Turanic St Parentucellia viscosa (L.) Caruel T Atlantic Parietaria diffusa M. et K. H Euri-Mediterranean Parthenocissus quinquefolia (L.) Planchon P Alien N Amer nat Petrorhagia prolifera (L.) Ball et Heyw. T Euri-Mediterranean Phalaris bulbosa L. H Steno-Mediterranean Phalaris coerulescens Desf. H Steno-Mediterranean Phalaris truncata Guss. H Euri-Mediterranean Phleum pratense L. H Circumboreal F-B Phragmites australis (Cav.) Trin. G Cosmopolitan hy Picris echioides L. T Euri-Mediterranean St Picris hieracioides L. H Circumboreal St Pyrus pyraster Burgsd. P Eurasiatic Q-F Pisum sativum L. T Steno-Mediterranean Plantago lanceolata L. H Eurasiatic M-A Poa annua L. T Cosmopolitan St Poa trivialis L. H Eurasiatic M-A Polypogon monspeliensis (L.) Desf. T Subtropical Populus alba L. P Eurasiatic hy Populus nigra L. P Eurasiatic hy Portulaca oleracea L. T Cosmopolitan St Potentilla reptans L. H Eurasiatic Prunus armeniaca L. P Alien hort. cas Prunus persica (L.) Batsch P Alien hort. cas Prunus cerasifera Ehrh. P Alien Eur, Asia cas Prunus spinosa L. P Eurasiatic R-P Pteridium aquilinum (L.) Kuhn G Cosmopolitan Tab. 1. – continued 238 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Pulicaria dysenterica (L.) Bernh. H Euri-Mediterranean Pyracantha coccinea Roemer P Steno-Mediterranean R-P Pyrus pyraster Burgsd. P Eurasiatic Q-F Quercus robur L. P Eurasiatic hy Ranunculus bulbosus L. H Eurasiatic F-B Raphanus raphanistrum L. T Euri-Mediterranean St Rapistrum rugosum (L.) All. T Euri-Mediterranean Reichardia picroides (L.) Roth H Steno-Mediterranean T-Brom Reseda phyteuma L. T Euri-Mediterranean St Robinia pseudoacacia L. P Alien N Amer inv Rosa canina L. P Eurasiatic R-P Rosa sempervirens L. P Steno-Mediterranean Qi intbl Rubia peregrina L. P Steno-Mediterranean Qi Rubus ulmifolius Schott P Euri-Mediterranean R-P Rumex conglomeratus Murray H Eurasiatic Rumex crispus L. H Cosmopolitan Rumex obtusifolius L. H Eurasiatic G-U Rumex pulcher L. H Euri-Mediterranean Salix alba L. P Eurasiatic hy Salvia verbenaca L. H Atlantic Sambucus ebulus L. G Euri-Mediterranean G-U Sanguisorba minor Scop. H Eurasiatic F-B Saponaria officinalis L. H Circumboreal hy Scabiosa maritima L. H(b) Steno-Mediterranean F-B Scorpiurus muricatus L. T Euri-Mediterranean Hg Securigera securidaca (L.) Deg. et Doerfl. T Euri-Mediterranean Hg Senecio vulgaris L. T Euri-Mediterranean St Setaria verticillata (L.) Beauv. T Subtropical Setaria viridis (L.) Beauv. T Cosmopolitan St Sherardia arvensis L. T Euri-Mediterranean St Silene alba (Miller) Krause H(b) Eurasiatic Av Silene bellidifolia Juss. T Steno-Mediterranean Silene latifolia Poiret H(b) Steno-Mediterranean G-U Silene vulgaris (Moench) Garcke H Eurasiatic Sinapis arvensis L. T Steno-Mediterranean St Solanum nigrum L. T Cosmopolitan St Sonchus asper (L.) Hill T Eurasiatic St Sonchus oleraceus L. T Eurasiatic St Sonchus tenerrimus L. T Steno-Mediterranean St Sorghum halepense (L.) Pers. G Alien Afr, Asia inv Spartium junceum L. P Euri-Mediterranean R-P Stachys ocymastrum (L.) Briq. T Steno-Mediterranean Stellaria media (L.) Vill. T Cosmopolitan St Tab. 1. – continued ACTA BOT. CROAT. 71 (2), 2012 239 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Species Life form Geographic element Origin of aliens Status of aliens (Lazio) Vegeta- tion units Sylibum marianum (L.) Gaertner H(b) Medit.-Turanic G-U Taraxacum officinale Weber H Circumboreal M-A Thymus vulgaris L. Ch Steno-Mediterranean C-M Tolpis virgata (Desf.) Bertol. H Steno-Mediterranean St Torilis arvensis (Hudson) Link T Cosmopolitan Tragopogon porrifolius L. H(b) Euri-Mediterranean Av Trifolium angustifolium L. T Euri-Mediterranean T-Brom Trifolium arvense L. T Eurasiatic Trifolium campestre Schreber T Eurasiatic St Trifolium fragiferum L. H Eurasiatic Trifolium ochroleucum Hudson H Eurasiatic F-B Trifolium pratense L. H Circumboreal M-A Trifolium subterraneum L. T Euri-Mediterranean Trisetaria panicea (Lam.) Maire T Steno-Mediterranean T-Brom Tussilago farfara L. G Eurasiatic Av Typha latifolia L. G Cosmopolitan hy Ulmus minor Miller P Eurasiatic Q-F Urospermum dalechampii (L.) Schmidt H Euri-Mediterranean T-Brom Urtica dioica L. H Cosmopolitan G-U Urtica membranacea Poiret T Steno-Mediterranean St Valerianella eriocarpa Desv. T Steno-Mediterranean St Verbascum blattaria L. H(b) Eurasiatic Av Verbascum densiflorum Bertol. H(b) Euri-Mediterranean Av Verbascum pulverulentum Vill. H(b) Eurasiatic Av Verbascum sinuatum L. H(b) Euri-Mediterranean Av Verbena officinalis L. H Eurasiatic St Veronica arvensis L. T Eurasiatic St Veronica cymbalaria Bodard T Euri-Mediterranean Veronica hederifolia L. T Eurasiatic St Veronica persica Poiret T Alien Asia inv Vicia bithynica (L.) L. T Euri-Mediterranean Vicia hirsuta (L.) Gray T Eurasiatic Vicia hybrida L. T Euri-Mediterranean Vicia lutea L. T Euri-Mediterranean St Vicia sativa L. T Medit.-Turanic St Vicia villosa Roth T Euri-Mediterranean T-Brom Vitis vinifera L. P Alien hort. cas Vulpia ciliata (Danth.) Link T Euri-Mediterranean T-Brom Vulpia ligustica (All.) Link T Steno-Mediterranean T-Brom Zea mays L. T Alien hort. cas Tab. 1. – continued embankment communities are either biennial or rosulate plants: typical examples include Daucus carota, Malva sylvestris, Plantago lanceolata, Picris hieracioides, and four different Verbascum species. Phanerophytes featured 13% of the recorded flora (37 species). The geographic element with the highest number of species (Fig. 2) was the Eurasiatic (ca. 30%), followed by euri-Mediterranean and steno-Mediterranean elements – however, the sum of these latter (and of the Mediterranean-Turanic element) is ca 44% of the recorded flora. Alien species (including taxa that originated as cultivated plants) accounted for 8.4%. Alien species classified as »invasive« in Lazio were 4% of the recorded flora. In the phytosociological spectrum (Fig. 3), the largest element (75 species, i.e. 26%) was made up by species from Stellarietea mediae, but 20 out of these 75 species belong to the Thero-Brometalia order. Species from Festuco-Brometea are also represented in the embank- ment flora (16 species, 5.6%), while the Molinio-Arrhenateretea element is poorer (8 species). Artemisietea vulgaris class is represented by 19 species (6.6%), and Galio-Urticetea features only 10 species (3.5 %). A total of 26 species (9.1%) belongs to the floristic assemblage of forest or forest-edge communities. Finally, 6.3% of the flora is made up of species from hygrophilous syntaxa. Discussion The total richness found (with more than 200 taxa recorded in the first 1,000 m) is considerably high compared to some north European studies on railways (cf. e.g. MESSEN- GER 1968, NIEMI 1969, LEJMBACH et al. 1975), but is consistent with the high floristic richness of Mediterranean landscapes (the Lazio region has 3,228 taxa: CONTI et al. 2005) and with species-area patterns known for central Italy (CHIARUCCI et al. 2012). In the family spectrum, the richest families recorded from the embankment are the same as in the whole Italian flora (ABBATE et al. 2007), however in the embankment flora there is an anomalous proportion of Scrophulariaceae, Lamiaceae and Boraginaceae, due to the disturbance regime of the railway sides, which promotes the diversity of ruderal and/or biennial species 240 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Fig. 2. Geographic elements in the flora of the railway segment. For explanations see table 1. – particularly well represented in these families. The most common annuals in the embank- ment flora included Avena barbata, Bromus madritensis, Papaver rhoeas and Sherardia arvensis (CORNELINI 1994b). The life-form distribution, despite the artificial and recent origin of the study site, keeps a strong similarity with the spectrum of the regional pool (Fig. 4). Annuals feature a higher proportion than in the flora of Lazio (38% vs. 33%), as expected due to three co-occurring factors: the warm climate belt where the study area is located; the dry topsoil of the embankment; and the disturbance caused by mowing of the embankment slopes. The proportion of therophytes found here is much lower than that recorded in a railway station in Rome by CORNELINI and PETRELLA (1996), where 50% of a 266-species flora was made up of annuals – however, the two study sites are not comparable as the railway station includes large paved areas and/or highly disturbed habitats, and it is surrounded by a completely urbanized district. Perennial herbs have a slightly higher proportion in the embankment assemblage than in the regional flora. The richness of biennial and rosulate Hemicryptophytes is well known to be connected to the features of railway verges (TINNER and SCHUMACHER 2004, NOWI�SKA and CZARNA 2008): traits such as buds very close to the ground, long taproots and flat rosettes allow survival in spite of frequent mechanical mowing. Geophytes, although with a lower percentage than in the regional flora, are well-represented, since these plants are favorably selected by an intermediate intensity of mechanical disturbance – as already observed e.g. in the archaeological areas in downtown Rome (CELESTI-GRAPOW et al. 1989, CELESTI-GRAPOW 1995). Among the Geophytes found in the embankment flora, ACTA BOT. CROAT. 71 (2), 2012 241 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Fig. 3. Proportion of character species of different syntaxa in the flora of the railway segment. the most noteworthy include an orchid, Ophrys apifera, and Cyclamen hederifolium, a species usually bound to the shady understorey of sub-Mediterranean woods. On the other hand, the high proportion of Phanerophytes highlights the role played by the railway sides as a substitute habitat for woody species, within an intensively farmed landscape devoid of suitable microsites such as hedgerows or dry stone walls. In fact, among the Phanerophytes recorded on the rail embankment, there are species from different vegetation series of the toposequence of the Tiber valley, and from different seral stages of each vegetation series: Populus alba and Salix alba are trees from the river-side forest vegetation (CESCHIN and SALERNO 2008); Fraxinus oxycarpa and Quercus robur are trees which potentially dominate the alluvial, hygro-mesophytic plains (BLASI et al. 2010); Cornus sanguinea and Euonymus europaeus are shrubby species from the wood edges of the alluvial plain forest (CESCHIN and SALERNO 2008); Fraxinus ornus and Pyrus pyraster are small trees of the thermophylous Quercus cerris woods of the hill slopes (BLASI et al. 2004); Cercis siliquastrum, Crataegus monogyna and Pyracantha coccinea are found in the wood edges and shrubby seral stages of the Q.cerris forests (BLASI et al. 2004); Celtis australis and Ficus carica are often found on the pyroclastic cliffs and boulders (SCOPPOLA and FILIBECK 2008). As for the geographic element distribution (Fig. 2), the Mediterranean element (in a wide sense) prevails in the studied railway side flora (ca. 44%), suggesting that the Mediter- ranean climate acts as a strong ecological filter, so that a marked link with the regional species pool is preserved even in a completely artificial habitat. The richness of alien species found in the study site (8.4%) is relatively low for an artificial, disturbed habitat, considering that in the chorological spectrum of the whole flora of the Lazio region alien units reach 10.4% (CONTI et al. 2005). Studies from central Euro- pean railway floras found percentages of alien species up to 36% (Fig. 5) (LEJMBACH et al. 1975, TINNER and SCHUMACHER 2004, NOWI�SKA and CZARNA 2008, WARCHOLI�SKA and SUWARA-SZMIGIELSKA 2009). However, these studies are not fully comparable with the present work, as they include (or are limited to) stations and/or urban habitats. Alien therophytes are a group that in central and north Europe is often reported to play a significant role in the flora of railway areas (e.g. NIEMI 1969, BRANDES 1983, TINNER and SCHUMACHER 2004, GALERA et al. 2011). For instance, in a floristic study on railway lines and 242 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. Fig. 4. Comparison between the life-form distribution in the embankment flora (black columns) and in the flora of Lazio region (grey columns). For legend of Life forms, see table 1. stations of Pomerania (LEJMBACH et al. 1975), 22.3% of the total railway flora was made up of alien therophytes (including alien biennial-hemicryptophytes). This group, by contrast, had a very low diversity in our survey: only 6 species (2.1%) of exotic annuals were found (Amaranthus retroflexus, Conyza bonariensis, Conyza canadensis, Euphorbia prostrata, Veronica persica, Zea mays). Although our result could be influenced by the fact that in the present study the ballast was not surveyed, it has already been underlined that in the floras of Mediterranean cities (e.g. CELESTI-GRAPOW 1995, CELESTI-GRAPOW et al. 1997) alien annuals are not as characteristic as they are in central European urban environments. This is because in the Temperate biome artificial habitats perform as extrazonal, dry and warm micro- -environments: the local species are less adapted to this niche, which is more competitively exploited by aliens from warmer countries. In the Mediterranean biome, instead, xeric conditions are widespread and thus railway grounds do not perform as especially favorable sites for therophytes (BRANDES 1993: 441). In the phytosociological spectrum (Fig. 3), the richest group (26%) is made up by species recognized as characteristic taxa of Stellarietea mediae (or of its subordinate orders), i.e. the widely-distributed class of the annual, ruderal communities (according to GRIME et al. 1988), bound to highly disturbed or anthropogenic soils (e.g. MUCINA et al. 1993). However, a large share of the Stellarietea species recorded in the embankment flora is accounted for by taxa belonging to the order Thero-Brometalia (=Brometalia rubenti-tectorum) and in particular to the Echio-Galactition alliance, i.e. to the Mediterranean, sub-nitrophilous and medium- -sized annual vegetation communities of fallow land, minor-road sides and other edge ha- ACTA BOT. CROAT. 71 (2), 2012 243 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT Fig. 5. Proportion of alien species recorded in various railway floras: a) present study (8.4%); b) rail- way stations of NE-Switzerland (19.6%) (TINNER and SCHUMACHER 2004); c) Powodowo station, W-Poland (25.7%) (NOWI�SKA and CZARNA 2008); d) railway lines and stations of Pomerania, N-Poland (27.7%) (LEJMBACH et al. 1975); e) urban railways and stations in Pabianice, C-Poland (36.4%) (WARCHOLI�SKA and SUWARA-SZMIGIELSKA 2009). bitats (IZCO 1977, GIGANTE and VENANZONI 2007). All these species (e.g. Avena barbata, Bromus hordeaceus, Dasypyrum villosum, Lotus ornithopodioides, Medicago orbicularis, Reichardia picroides), although with a partially ruderal character, have a decidedly xerophi- lous ecology and a strictly Mediterranean range – so that many of them were until recently classified among the characteristic species of the natural and semi-natural Mediterranean annual grasslands of Helianthemetea guttati (=Thero-Brachypodietea) (e.g. RIVAS-MARTINEZ 1977, FANELLI and LUCCHESE 1998). Further, even this latter class, interpreted in a narrower sense (i.e. without the above mentioned sub-nitrophilous species), is represented in our survey by a significant group of species (e.g. Briza maxima, Blackstonia perfoliata, Hypochoeris achyrophorus, Scorpiurus muricatus). On the other hand, the taxa from Artemisietea vulgaris [i.e. the Euro-Siberian communities of perennial, nitrophilous to sub-nitrophilous herbs and grasses with an intermediate C-R behaviour (according to GRIME et al., 1988), usually typical of road- and railway-sides (MUCINA et al. 1993)] are not particularly numerous in the embankment (19 species, 6.6%), as their functional traits are scarcely adapted to the Medi- terranean climate. The same holds for the species from Galio-Urticetea (wood- and road- -fringe communities of nitrophilous, tall herbs with a C-R or C strategy) (MUCINA et al. 1993), featuring only 10 species (3.5 %) and from Molinio-Arrhenateretea (nitrogen-rich and mesophytic anthropogenic hay-meadows of the temperate region) (8 species). We defined as forest species (9.1%) the taxa known as characteristic species of the following classes (or subordinate syntaxa): Quercetea ilicis (Mediterranean evergreen woods and maquis: e.g. Rubia peregrina, Asparagus acutifolius); Querco-Fagetea (European deciduous forests – namely, in the surroundings of the study area, sub-Mediterranean thermophilous deciduous forests of the order Quercetalia pubescenti-petraeae: e.g. Cyclamen hederifolium, Cercis siliquastrum, Fraxinus ornus); Rhamno-Prunetea (deciduous forest-edge shrublands: e.g. Crataegus monogyna, Prunus spinosa); Trifolio-Geranietea (communities of the partially shaded, herbaceous fringes at the edge of deciduous woodlands; e.g. Agrimonia eupatoria, Holcus lanatus, Lathyrus sylvestris, Origanum vulgare, Sanguisorba minor). Species from (woody or herbaceous) hygrophilous syntaxa (Lemnetea, Phragmito-Magnocaricetea, Sa- licetea purpureae, Populetalia albae) are also found in a noteworthy proportion (6.3 %): these plants (e.g. Alisma plantago-aquatica, Carex otrubae, Lemna minor, Typha latifolia) are common within the surveyed railway sides because of the numerous drainage ditches at the foot of the embankment – and because the vicinity of the river Tiber is a source of propagules (cf. CESCHIN and SALERNO 2008). Thus, the spectrum of the original plant communities of the recorded species shows that the flora of the studied railway section is only partially »ruderalized«: on the contrary, it seems to keep a strong link with the floristic composition of the plant communities of its biogeographic context. This confirms the suggestion of a comparative study on urban floras of Italy (CELESTI-GRAPOW et al. 1997), where the floristic assemblage in cities belonging to the Mediterranean sector of the country was found to have a high degree of similarity with the floristic composition of the surrounding (semi-)natural landscapes, while such a correla- tion was much weaker in cities of the temperate sector of Italy. Further, the different ecological elements that can be traced in the recorded flora under- line the extremely high heterogeneity of micro-habitats within the railway sides, and hence their potential importance for biodiversity: the co-occurrence in the surveyed flora of, for 244 ACTA BOT. CROAT. 71 (2), 2012 FILIBECK G., CORNELINI P., PETRELLA P. instance, hygrophytes such as Salix alba and xerophytes such as Micromeria graeca highlights the very steep gradient taking place within the 20-m wide embankment. In contrast to many central and north European studies (RANTA 2008 with references), no National/Regional Red List taxa or other particularly rare species were found. However, in temperate Europe rail verges have a high percentage of rare/endangered species because they provide a much drier micro-habitat than the surrounding landscape (BRANDES 1993), and thus are capable of hosting extrazonal Mediterranean taxa and other thermophilous plants (which include many of the Red List species in central European countries). As for boreal Europe, semi-natural grasslands (meadows and pastures which have originated from grazing and hay-making on natural grasslands and in woodlands) account for up to 25% of the endangered plant species, and are a particularly threatened habitat-type because of the cessation of grazing and mowing and their conversion to arable and afforested land (TIKKA et al. 2000, 2001): for these reasons, mowed road- and rail-verges are nowadays among the largest surviving areas of grassland habitats in north Europe. This is not applicable in Medi- terranean Europe, where dry habitats are the rule rather than the exception, and where grass- lands are still widely represented (BLASI et al. 2007, 2010). Thus, in south Europe road and rail verges are not necessarily valuable habitats in every landscape context, and probably do not play a significant role for endangered species. However, in the highly transformed land- scape of the present study, the railway sides provided a decidedly less disturbed habitat (al- though on a completely artificial soil), containing a significant sample of the floristic assem- blages of many different natural and semi-natural communities of a wider area – thus probably playing an important role, at a local scale, in maintaining diversity patterns and in providing corridors through an unfavorable landscape matrix. The present work was the first study carried out in Italy – and probably in Mediterranean Europe – on the floristic composition of a long railway segment beyond rail stations or urban areas, and perhaps the first study ever performed in Europe on a high-speed line. The floristic assemblage recorded in the studied rail embankment suggests that the ecological filter operated by the Mediterranean macroclimate prevents both complete »ruderalization« and »floristic homogenization« in the flora of even a highly artificial habitat – by contrast to what is observed in Temperate Europe and north America, where floras of anthropogenic habitats from different countries were found to be more similar to each other than to the surrounding (semi-) natural habitats (WITTIG and BECKER 2010). Further studies gathering a large amount of floristic data from railway grounds and other artificial habitats in south Europe are needed to confirm what is suggested by the present work. This is relevant also for planning restoration practices of artificial substrata (embank- ments, road cuts, etc.), since it means that in the Mediterranean region the climate prevails over the edaphic filter. Thus, the surrounding natural communities can provide a good reference list for choosing the species to be used for revegetation practices, and, as tested by recent studies in Mediterranean areas (BOCHET et al. 2007, MOLA et al. 2011), it is even possible to rely only on natural colonization processes. Further, as already found in central and north Europe (TIKKA et al. 2000; 2001, TINNER and SCHUMACHER 2004, RANTA 2008, LOSOSOVA and LANIKOVA 2010), in the Mediterranean region too railway sides can act as a substitute habitat for species from natural and semi-natural communities. However, the ecological role of railway sides in the temperate ACTA BOT. CROAT. 71 (2), 2012 245 FLORA OF A HIGH-SPEED RAILWAY EMBANKMENT and boreal regions – where road and railway verges are among the few surviving examples of dry and mowed habitats – is quite different compared to the Mediterranean countries. 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