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AKMAN, Y., Ankara Universiti-Fen Facultesi-Biyologie Bolumu,Ankara, Turquie.AUSSENAC, G., INRA, CNRF, Unité de Recherches en Bioclimatolo-gie Forestière, Champenoux, F 54280 Seichamps.BARBAULT, R., ENS, 46 rue d'Ulm, F 75230 Paris Cedex 05.BARBERO, M., UAM III, Faculté de Saint Jérôme, Laboratoire deBotanique et Ecologie Méditerranéenne (Case 461), Avenue escadrilleNormandie-Niemen, F 13397 Marseille Cedex 13.BIROT, Y., INRA, Département des Recherches Forestières, AvenueVivaldi, F 84000 Avignon.BONIN, G., UAM 1, Laboratoire de Biosystématique, Faculté de SaintJérôme, F 13397 Marseille Cedex 13.BOTTEMA, S., Biologisch-Archaeologisch Institut, RijksuniversiteitGroningen, Poststraat 6, NL-9712, Groningen, Pays-bas.BOUDOURESQUE, C.·F., UAM II, Faculté des Sciences de Luminy,LBMEB, (Case 901), F 13288 Marseille Cedex 9.BOUVAREL, P., Thibompré, F 88480 Saint Rémy.CATARINO, F.M., Museu, Laboratorio e Jardim Botanico, Faculdadede Ciencias, rua da Escola Politechnica, P 1294 Lisboa Codex.CHAMPEAU, M., UAM 1, Faculté des Sciences Saint Charles, 3 placeVictor Hugo, F 13003 Marseille Cedex.COSTA, M., Facultad deFarmacia, Departamento de Botanica, AvenidaBlasco lbanez 13,46010 Valencia, Espagne.DAGET, P., Université de Montpellier II, Institut de Botanique, Labora-toire de Systématique et Botanique méditerranéennes, 163 rue AugusteBroussonet F 34000 Montpellier.DANIN, A., The Hebrew University of Jerusalem, Department of Bota-ny, Jerusalem, Israël 91904.DEBUSSCHE, M., CNRS-CEPE, Centre d'Ecologie Fonctionnelle etEvolutive, Route de Mende, BP 5051, F 34033 Montpellier Cedex.DJEBAILI, S., Université des Sciences et de la Technologie HouariBoumedienne, INA, BP 9, Dar el-Beida, Alger, Algérie.DODD, R.S., University of California, Forest Products LaboratoryRichmond, Berkeley, CA-94804, Etats Unis d'Amérique.DuMERLE, P., INRA, Station de Zoologie Forestière, Avenue Vivaldi,F 84000 Avignon.GHABBOUR, S., Institut of African Research and Studies, Departmentof Natural Resources, Cairo University, Giza, Egypte.GIUDICELLI, J., UAM III, Faculté de Saint Jérôme, Laboratoired'Ecologie Animale, Avenue escadrille Normandie-Niemen, F 13397Marseille Cedex 13.GONZALEZ·BERNALDEZ, F., Universita Autonomia de Madrid,Facultad de Ciencias, Catedra de Ecologia, Ciudad Universitaria deCanto Blanco, 28049 Madrid, Espagne.LAMOTTE, M., ENS, Laboratoire de Zoologie, 46 rue d'Ulm, F 75230Paris 05.LEFEUVRE, J .•c., MNHN,.Laboratoire de l'Evolution des SystèmesNaturels et Modifiés, 57 rue Cuvier, r 75231 Paris Cedex 13.

LEMEE, G., 6 Avenue Garennière, F 94260 Fresnes.LOWE, J.J., Royal Holloway and Bedford New College, DepartmentofGeography, Egham, Surrey TW20 OEX, Royaume Uni.LUMARET, R., CNRS-CEPE, Centre d'Ecologie Fonctionnelle etEvolutive, Route de Mende, BP 5051, F 34033 Montpellier Cedex.MARGARIS, N.S., University of the Aegean, Department of Environ-mental Studies, 17 Karadotni str., 81100 Mytilène, Grèce.M'HIRIT, O., Direction des Eaux et Forêts et de la Conservation desSols, Division de Recherches et d'Expérimentations Forestières, ChariaOmar ibn El-Khattab, BP 763, Rabat (Agdal), Maroc.MUNAUT, A.V., Université Catholique de Louvain, Laboratoire dePalynologie et Dendrochronologie, 4 Place Croix-du-Sud, B 1348 Lou-vain-la-Neuve.NAHAL, 1., Université d'Alep, Faculté d'Agronomie, Laboratoire deBotanique, Alep, Syrie.OECHEL, W., San Diego State University, Colleges of Sciences, De-partment of Biology, San Diego, CA 92182-0057, Etats Unis d'Améri-que.OZENDA, P., Université Joseph Fourier, Laboratoires d'Ecologie Vé-gétale, BP 53 X, F 38041 Grenoble Cedex.PEDROïfl, F., Università degli Studi di Camerino, Dipartimento diBotanica ed Ecologia, Via Pontoni 5, 162032 Camerino.PIUSSI, P., Università degli Studi di Firenze, Istituto di Selvicoltura, ViaS. Bonaventura 13,150145 Firenze.PONS, A., UAM III, Faculté des Sciences de Saint Jérôme, Laboratoirede Botanique Historique et Palynologie (Case 451), F 13397 MarseilleCedex 13.RASMONT, P., Université de Mons, Laboratoire de Zoologie, AvenueMaistriau, B 7000 Mons.RIOUX, J.·A., Université de Montpellier, Faculté de Médecine, Labora-toire d'Ecologie Médicale et Pathologie Parasitaire, 163 rue AugusteBroussonet, F 34000 Montpellier.RIVAS·MARTINEZ, S., Universidad Complutense, Faeultad de Far-macia, Departamento de Botanica, Madrid 3, Espagne.ROMANE, F., CNRS-CEPE, Centre d'Ecologie FonetionnelleetEvolu-tive, Route de Mende, BP 5051, F 34033 Montpellier Cedex.RUNDEL, P.W., University of Califomia, Laboratory of Biomedicaland Environmental Sciences, 900 Veteran Avenue, Los Angeles, CA90024-1786, Etats Unis d'Amérique.SPECHT, R.L., The University of Queensland, Botany Department, StLucia, Queensland 4072, Australie.TERRADAS, J., Universitat AUlonomia de Barcelona, Centre de Recer·ca Ecologica i Applicacions Forestals, 08193 Bellaterra (Barcelona),Espagne.TAYLOR, H.C., Botanical Research Unit, POBox471, 76000Stellen·bosch, République Sud-Africaine.VAN DEN MAAREL, E., Vaxtbiologiska Institutionen, Box 559, S75122 Uppsala l, Suède.

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ECOLOGIA MEDITERRANEA XX (314) 1994 : 85-94

The vegetation of the Comacchio Saltern (Northern Adriaticcoast, Italy)

Filippo PICCOLI*, Nicola MERLONI** and Mauro PELLIZZARI***

ABSTRACT

The vegetation of the Comacchio Saltem was studiedwith the phytosociological method and the data processedwith numerical methods. In this biotope, whose activity of salt production was terminated in 1984, seven associationshave been found, some having marked phytogeographic interest, namely Pucinellio convolutae •Arthrocnemetumglauci with the subassociations typicum and halocnemetosum strobilacei. The main ecological factors whichdetermine the various distributions of the vegetational types are the level and salinity of the water.

KEYWORDS : halophilous vegetation, ecology, numerical analysis, saltern, Northern Adriaticcoast.

RESUME

La vegetation de la Saline de Comacchio a ete etudiee selon la methode de Braun-Blanquet. Les releves ontete classes par des methodes d'analyse numerique. Dans ce biotope dont la production du sel a eoo arretee en 1984,7 associationsontetemises en evidence, quelques-unes entreelles tres interessantes au pointde vuephytogeographiqueet en particulier Puccinellio convolutae • Arthrocnemetum glauci subass. typicum et halocnemetosum strobilacei.Les principaux facteurs ecologiques qui determinent la distribution des types de vegetation sont le niveau et la salinitede l'eau.

MOTS-CLES : vegetation halophile, ecologie, analyse numerique, saline, cote nord-adriatique

INTRODUCTION

The Comacchio Saltern was created in1810 to deal with the salt shortage resulting fromwar. It was set up in a part of the northeastterritoryofthe Valli di Comacchio,well-suited tothis purpose (figure 1). These basins spread outpeacefully and are in communication with theAdriatic Sea by means of locks. Their water ischaracterized by shallow depth and salinity that

* Istituto di Botanica dell'Universita, Corso Porta Mare, 244100 Ferrara, Italy.

** Piazza A. Costa, 15 - 48015 Cervia, Italy.*** Via Assiderato, 29 - 44100 Ferrara, Italy.

varies in the course of the year. The territory ofthe Saltern (518 ha) is structurally composed ofareas having various configurations in relationto the different production phases of salt: thestorage basins and the first evaporation pondspresent irregular morphologies and reveal theirmembership in the biotope from which theyoriginate, while the second and third evapora-tion ponds, the salting basins and the canalsystem correspond toman-made structures hav-ing a very regular morphology.

The activity of salt production proceededfor 174 years, until 1984, when the State Mo-nopolydecided to suspend itwith the consequent

86 The vegetation ofthe Comacchio Saltern

COMACCHIOSAlTERN

!0!

-0(;)

Po Rivl'r 0<>.rf'

Figure 1.- Map showing the Comacchio Saltern and its surrounding area

shut-down of the production plants and generalabandon of the site. Recently there have beenmany requests for the rehabilitation and better-ment of the Saltern, mainly for didactic andconservation purposes. It is, in fact, an environ-ment that offers great possibilities for naturestudy, as well as cultu.ral andinterest. The Comacchlo Saltern IS 10cluded 10one of the six stations of the Regional Park of thePoDeltaand is situated in proximityofarecentlyrestoredopen-airmuseum complex. An itineraryin this area evidences the attractions of the la-goons which, as is well-known, constitute animportant wetland of international renoun asestablished by the Ramsar Convention.

Specific flora and vegetation research hasnever been carried out on the territory in ques-tion; only a few mentions can be found inVALLIERI (1987) and ROSSI et al. (1988).

CLIMATE

The study area has a submediterraneanclimate. The climatic data collected during theperiod 1961-1980 at Valle Pega (circa 7 kmaway) are summarized in the diagram offigure2,which clearly shows that the precipitation hasthreemaximumswith amarkedperiodofdroughtin summer.

FLORA

Due to the strongly limiting factor of thehigh salt content in the water and soil, the floraconsists predominantly of halophilic species.Where the influence ofthe salt factordiminishes,salt-tolerant species develop as well as a consid-erable contingent ofnitrophilic species, diffusedin the vicinity of the man-made structures andpaths connectedwith the salt production activity.

The vegetation ofthe Comacchio Saltern

VAllE PEGA[20]

(-1m)

87

534mm

30

20

10

60

40

20

Figure 2.- Climodiagram referred to Valle Pega

The list of the species that have beencounted amounts to 140 taxa, of which 5 newspecies for the province ofFerrara are worthy ofspecial mention :

Centauriumtenuijlorum (Hoffmg. etLink)Frietsch - paleotemperate species rare in Italy.

Tragopogon dubius Scop. - pontic speciesrare in Italy.

Both species are diffused in the Elytrigiaatherica -community.

Linum strictum L. subsp. corymbulosum(Rchb.) Rouy - Stenomediterranean species con-sidered rare in northern Italy. Present on thebanks and paths arid during the summer season.

Halocnemum strobilaceum (Pallas) Bieb.Submediterranean species rare in Italy, diffusedin the southern end of the peninsula, Sicily andSardinia. CORBETIA (1976) cited it for theEmilia-Romagna coast in the province of Ra-venna, while recently ARRIGONI et al. (1985)noted it for the coastofTuscany.TheComacchioSaltern is the northernmost station on the Medi-

terranean coasts found todate. It is diffused in thePuccinellio convolutae-Arthrocnemetum glaucion the low banks of the second evaporationponds, where the soil presents salt efflorescencein summer.

Anthriscus caucalisBieb. -Paleotemperatespecies rare in Italy, diffused in zones containinga lot of rubble.

Arundo pliniana Turra, Bupleurumtenuissimum L. and Inula conyza DC. are alsorare locally. Among the species protected byRegional Law there are Limonium serotinum(Rchb.) Pign., L. virgatum (Willd.) Fourr. andL.bellidifolium (Gouan) Dum. FurthermoreSalicornia venetaPign. etLausi is included in thelist of species to be safeguarded in accordancewith EEC directive nr.92/43.

METHODS

The releves of the vegetation were carriedout following the Braun-Blanquet method.

88

After eliminating the species present onlyonce with negligible cover values, the releveswere submitted to classification and ordering.The formerwas performedby theSumofSquaresAgglomeration method based on the chord dis-tance (Euclideandistance on normalized quadratvectors), the latter by Principal ComponentsAnalysis based on the same chord distance ma-trix. These calculations are based on cover datacorresponding to the transformations of theBraun-Blanquet scale as proposed by van derMAAREL (1979). Descriptions of the numericalmethods employed are given by ORLOCI (1978)and LAGONEGRO & PEOLl (1985).

The phytosociological syntaxonomy is inaccordance with GEHU et al. (1984a, 1984c)whenever possible. Species nomenclature fol-

The vegetation ofthe Comacchio Saltern

lows PIGNATIl (1982), except for Elytrigiaatherica (Link.)Kerguelen andSalicorniapatulaDuval-Jouve.

RESULTS

Phytosociological evaluation of the vegeta-tion types

The distinct geomorphological features ofthe evaporation ponds and their separation banksare the basis of the distinction of the plantcommunities, which can be identified accordingto the environment in which they develop. Asyntaxonomical scheme of the surveyed com-munities is shown in table 1.

Table 1Syntaxonomical scheme of the surveyed communities

THERO-SALICORNIETEA Pign. 53 em. Tx. in Tx. et Oberd. 1958Pioneer halophilic vegetationThero-Salicornietalia Pign. 53 em. Tx. in Tx. et Oberd. 1958

Salicornion emerici Gehu 1984Salicornietum venetae Pign. 1966

Salicornion patulae Gehu 1984Suaedo-Salicornietum patulae (BrulIo et Fumari 1976) Gehu nom. novo

ARTHROCNEMETEA Br.-Bl. et Bolos 1957Perennial halophilic vegetation on saltmarshes

Arthrocnemetaliafruticosi Br.-Bt. 1931 corr. Bolos 1957Arthrocnemionfruticosi Br.-Bt. 1931 em. Riv.Mart. et al. 1980

Puccinellio festuciformis-Arthrocnemetumfruticosi (Br.-Bt. 1928) Gehu 1976Puccinellio convolutae-Arthrocnemetum glauci Br.-BI. (1928) 1933 Gehu nom. novo

JUNCETEA MARITIMI Br.-Bl. 1952Salty meadows

luncetalia maritimi Br.-Bt. 1931Puccinellion festuciformis Gehu et Scopp. 1984

Limonio-Puccinellietum palustris (Pign. 1966) Gehu et Scopp. 1984Agropyro-Artemision coerulescentis (Pign. 1953) Gehu et Scopp. 1984

Limonio-Artemisietum coerulescentis (pign. 1953) Gehu et Scopp. 1984

Halophytic vegetation

Salicornietum venetae (Table 2, releves 1-5)

This association sees the absolute pre-dominanceofthecharacteristic speciesSalicorniaveneta, an annual halophyte endemic to theNorth Adriatic coast, recognized and describedrecently by LAUSI (1969) and belonging to thegroup of tetraploid Salicornia becoming bright

red at the end of summer. Puccine/lia palustrisandArthrocnemumfruticosum follow with deci-sively low cover values.

The specific endemismofSalicorniavenetaalso corresponds to the endemism ofthe associa-tion, which has been found in the lagoons ofVenice and Marano but also extends to thesaltmarshes ofComacchioand theRavennacoast(PICCOLI et al., unpublished data).

The vegetation ofthe Comacchio Sa/tern 89

Table 2Phytosociological table: SV - Salicornietum venetae ; pp - Limonio-Puccinellietum palustris ;SP - Suaedo-Salicornietum patulae ; AF - Puccinellio festuciformis-Arthrocnemetumfruticosi ;

AG - Puccinellio convolutae-Arthrocnemetum glauci, ty - subass. typicum, hs - subass.halocnemetosum strobilacei; LA - Limonio-Artemisietum coerulescentis, AA - Elytrigia

atherica - community.The Braun-Blanquet cover values have been transformed in according to the van der Maarel

scale (1979) as follows: r=l, +=2, 1=3,2=5,3=7,4=8,5=9.

ss

35

5

z

RcIcY6 Do

9859933.2 .22 57.222222233.222223323222233233 .2

. 7 8 .. 3 2 .2 .323 75799999999898752 .. 22 .. 322 .22 .2

.2 .23353778787999888875773322 .2.55575

· 2 . 2 . 5 . . 33 .3999999899

. 5 5

. 2

.5723333.233 .323 . 7 . 2

. 5

. 3 . 2

. 3 3

· 2· 2

· 3 2. 2 . 2 2. 2

· 2· 2

· 2.22233233· 22 . 2

. 22 3

· 5

· 7

· 2 . 225

.2333· . 2 . 2

. 222· 2

. 2 2 . 22.2 .2 .3. .22

.23

.2. 2. 22.2

. 22 . 2

.2

S"licor,lia VCIICla

P"cci"dli" pal••',,;sSalico,.,.id pat••A,.tllrocII.m..m j,..'icos"".A,.,Arocllc",.", ,I"NCII'"Halocllem"", .trobilaec,,,,,Artemisia cocr,duc,,,,Agrop,roll P'"'g'''''UlvaluHIIUmiollc portll.lacoiduLimo"/,,... 61'0'1....'"Ad"ropu litoraU./rud" cr;tltneoidc,Limon;"". bellidj/oUamAsler ,,.;polilUllDad.,li. glomera'"Soru:I"u o/c,.IIc,,,.Allilllft viPl'."A,rop,roll clora'G''''''SIUJ,d" ".."itilfl4Limoni"". v/r,a'"".Parapltolis i"CllIrY4

Poa &ylvicolaHord,,,,,. mariti"."".BromlLf mollisP"r"pltolis s'ri,o••,8ro,"'1& molliformis

90

Salicornietum venetae grows on eitherslimy or clayey saline soils, which are flooded atlength during the adverse season but which dryout during summer, the period when the charac-teristic polygonal-shaped cracks occur. On thewhole the plant community is easily noticeablesince at the end ofsummer it presents in uniformpopulations, garishly tending toward a red col-our, at times very thick at times interrupted byzones with no vegetation.

Ithas beenobserved in the northern zone ofthe Saltern in a few second evaporation ponds.

GEHU (1989) and GEHU et al. (1984 b)emphasize the high nature study value and bio-genetic interest of this type ofvegetation, whosedistribution is so limited in space.

Suaedo-Salicornietum patulae (Table 1,releves 7-8)

An associationcharacterized bySalicorniapatula, an annual pioneerhalophyte belonging tothe diploid Salicornia group distributed in theMediterranean area (GEHU,1989).

In comparison with the previous associa-tion this communitydevelops at ahigherbionomiclevel on soils that dry out to a greater degree andmore rapidly during the course of the summer.

In the Saltern Suaedo-Salicornietumpatulae is quite rare, occupying a few spaces inthe Salicornietum venetae realm, where the soilis higher and thus subject to a briefer period ofsubmersion. For this reason only two releveswere performed and the characteristic specieswas found alone or in the company of very fewother plants.

It is a community that is not rare in theItalian coastal zones (GEHU et al. 1984a).

Puccinelliofestuciformis-Arthrocnemetumfruticosi (Table 2, releves 10-22)

Association of perennial halophytes thatdevelop on the saltmarshes with soil that isusually dry on the surface during summer, butmoist in depth.

The leading species are Arthrocnemumfruticosum and Puccinellia palustris (= P.festuciformis subsp.festuciformis), respectivelycharacteristic anddifferential ofassociation. Thelatter species, being endemic to the upper Adri-atic, qualifies numerous NorthAdriatic halophilicassociations with its presencewhich, in this way,

The vegetation ofthe Comacchio Saltern

acquire definite phytogeographic boundaries(GEHU et al. 1984b).

This paucispecific community is widelydiffused along the remaining Italiancoastswhere,however,P. palustris is replacedbyP. convoluta.

In the Saltem two subassociations can bedistinguished: typicum (Br.BI. 1952)Gehu 1976(releves 10-17) in the more humid places withrespect to the subassociation arthrocnemetosumglauci Gehu 1976 (releves 18-22) characteristicof a higher bionomic level and more arid soilduring the summer. Rarely developed on thebanks of the ponds, this association is for themost part present on the saltmarshes in the west-ern sector.

Puccinellio convolutae -Arthrocnemetumglauci (Table 2, releves 23-41)

Association of perennial halophytes thatdevelops on the low banks with a very salty soil,usually dry during the summer. In comparisonwith the previous association, it takes root at ahigher bionomic level in situations with southernexposure.

The leading species is Arthrocnemumglaucum as characteristic; the differential spe-cies Puccinellia convoluta is totally lacking, butit shouldbe said that it is alsoquite rare within theassociation nationally.

This association is known only for south-ern Italy and the islands (GEHU et al. 1984a).This should be put in relationship with thethermophilia of the characteristic species, whichis particularly favoured here by the markedlyhalomorphic soil conditions. Its presence in theSaltern is thus of particular phytogeographicinterest. Here it presents in two subassociations :typicumGehu et al. 1984 (releves 23-36), richerin species than the poorer halocnemetosumstrobilaceiGehu eta!. 1984 (releves 37-41), andalso able to push itself onto soils showing a saltefflorescence on the surface during summer, asin the second evaporation ponds.

The presence of the halocnemetosumsubassociation, discovered for the first time inthe province of Ferrara, increases the naturestudy interest and adds a Mediterranean note tothe territory surveyed.

The Comacchio Saltern represents thenorthernmost station of this vegetational unitfound diffused in the Mediterranean area, andshould be adequately safeguarded.

The vegetation ofthe Comacchio Sa/tern

Limonio - Puccinel/ietum palustris (Ta-ble 2, releves 6-7)

Meadow dominated by the perennialhalophilic grass Puccinellia palustris which de-velops on slimy-clayey soils with longperiodsofflooding and a variable, but in general modest,salt content. It is accompanied by a few speciesand a predominant layer ofgreen algae, Ulvales,which covers the soil at the baseofthe plan t. Thisconfirms themarked hygrophilia ofthis commu-nity, analogous to what is found in similarpopulations in «Sacca di Goro» (PICCOLI et al.,1991).

AlsoLimonio-Puccinellietum is to be con-sidered an association endemic to the NorthernAdriatic, as it is diffused only in the salty coastalenvironments from the Ferrara area up toGoriziacoast and for this reason it merits all the attentionofconservation as a highly significantelementofthe biologic heritage (GEHU et al., 1984b).

In the Saltern it covers modest surfacessituated in the northeast sector.

Limonio-Artemisietum coerulescentis (Ta-ble 2, releve 42)

Dense meadow that develops along thebanks not subject to prolonged flooding evenduring the unfavourable seasons. The character-istic species of association is Artemisiacoerulescens whereas Limonium serotinum isconsidered a differential species. The latter islacking in the only releve it was possible toperform in the Saltern (in the vicinity of theeastern basins), due to the meagre surface areacovered by this community, which is, however,well-documented in the Comacchio saltmarshes(CORBETIA, 1968), the Venetian lagoons(GEHU et al., 1984b), and the Bertuzzisaltmarshes (PICCOLI et al., unpublished).

In general the higher banks of the Salternare covered by a type of meadow which is verydiffused and where Elytrigia atherica, whichappears here as characteristic of a higher order,takes the upperhand to make up framing beltsthat are problematic and uncertain syntaxo-nomically.

Halotolerant vegetation

Elytrigia atherica- community (Table 2,releves 43-51)

This is acommunitywhosemeadowphysi-ognomy is totally given by the grass Elytrigia

91

atherica, a species that tolerates a certain salinecontent but that cannot be considered a realhalophyte. The numerous species that accom-pany it are quite heterogeneous: a part are typicalhalophytes, anotherhalotolerant, andmanygravi-tate in the classes of nitrophilic and infestingvegetation or mesophytic meadows.

In agreement with PIGNATTI (1966), whodescribed analogous populations in the Venetianlagoon, Agropyron littorale-community,Elytrigia atherica-community, is not a real asso-ciation. The weak salinity allows the infiltrationof quite varied elements which, in any case,except for Dactylis glomerata, are never con-stant in their presence.

Very similar meadows are diffused in allthe saltmarshes of the PoDelta, and on the sandyareas behind the sand dunes (FERRARI et al.,1985; PICCOLI et al., 1991).

Aeluropo littoralis-AgropyretumpungentisCorbetta and Pirone 89, described for the Ioniccoast (CORBETIA et al., 1989), presents deci-sively halophilic characteristics and does notseem to have analogies with our populations.

In the Saltern this typeofvegetation coversnearly all the banks surveyed which, if leftunattended, with the passing of time tend to hostmore complex shrubby communities belongingto the Prunetalia spinosae order; this evolutioncan be observed in the vicinity of«CasaBianca»,where species introduced as Elaeagnusangustifolia are also present.

Ecological Remarks

From the cluster analysis (Table 2), thefollowing emerges: at the higher hierarchic levelthe releves appeardivided in two groups: amoreconsistent one (41 releves) which includes themost markedly halo-hygrophilic situations and asmaller one (10 releves) of populations freerfrom water.

In the first group, starting from the left wehave the associations more linked to water :Salicornietum venetae (releves 1-5), Limonio-Puccinellietum palustris (releves 6-7), andSuaedo-Salicornietum patulae (releves 8-9).These three communities are directly connectedto Puccinellio festuciformis-Arthrocnemetumfruticosi, subdivided in the typicum (releves 10-17) and arthrocnemetosum glauci (releves 18-22) subassociations. The resulting group is fairlyclearly separated from the following group, con-sisting of Puccinellio convolutae-

92 The vegetation ofthe Comacchio Saltern

Arthrocnemetumglauci (releves 23-41). Withinthis association it is possible to distinguish agroup of re1eves characterized by the high pres-ence of Halocnemum strobilaceum(halocnemetosum subassociation, releves 37-41)extremelyinterestingin termsofphytogeography.

The second group of reIeves includesLimonio-Artemisietumcoerulescentis (releve42)and the Elytrigia atherica community (releves43-51). In both cases it is a matter of situationsfree ofwater to a great degree, andwhich usuallyappear on the most surveyed paths and knolls.

It seems evident from the clusters that thedifferent populations are ordered from left toright according to a decreasing degree ofhygrophilia.

Also the ordering procedure (figure 3),considered by various Authors as complemen-tary to the classification procedure, indicates aspatial division of the releves that it seems can beinterpreted in terms of degret!: of hygrophilia.Therelationshipsofsimilarity ),etween the relevesand the groups they give rise to also appear to beconfirmed.

I

•0 .,.:

··· •·. ;..···

Figure 3.- Ordering of the releves ofthe vegetation according to the first two principal components.DSalicornietum venetae; • Limonio-Puccinellietumpalustris ; 0 Suaedo-Salicornietumpatulae ;"Puccinelliofestuciformis-Arthrocnemetumfruticosi; * Puccinellio convolutae-Arthrocnemetumglauci, subass. typicum and *I subass. halocnemetosum strobilacei ;oLimonio-Artemisietum coerulescentis ; • Elytrigia atherica - community.

The vegetation ofthe Comacchio Saltern

CONCLUSIONS

Although being an environment for themost part artificial, in light our findings theComacchio Saltem displays flora and vegetationof unsuspected interest.

The halophilic types that have been foundare, in part, common to the ones pointed out inenvironments with similar ecology (Valli diComacchio, Valli Bertuzzi, and the «Pialasse»ofRavenna) and, in part, entirely original. ThePuccinellio convolutae-Arthrocnemetum glauciassociation in particular, never found up to nowin the territory of the Po Delta, is highly interest-ing and its presence seems to be determined,above all, by edaphic causes (salinity) rather thanby climatic causes. In fact, this association doesnot develop in the adjacent Valli di Comacchiowhich, being exploited for fisheries, receive asupply of fresh water and are regulated for theinlet of sea water. This confirms the «azonalvegetation» character of the halophilicpopulations, i.e. their widespread geographicdistribution, but strictly linked to very particularedaphic conditions which thus assume the role ofecologic factors, absolutely prevalent and deter-minant.

Considering the extreme rarefaction thatthe saline environments have undergone in theNorthern Adriatic littoral in the last decades,although being an artificial environment inmanyrespects, the Comacchio Salterns represent animpressive natural heritage for their value of«conservative» environment, not only for theflora and specialized vegetation but also for theinteresting birds that make their habitat here.Their maintainment as saltmarshes whose hy-drology is regulated by man is therefore to beaugured, disregardful of their direct economicproductivity.

The research was supported by a grant of P.I.M. (ProgrammaIntegrato Mediterraneo per le zone lagunari dell'Adriaticosettentrionale)andM.U.R.S.T.(MinisteroUniversitaeRicercaScientifica e Tecnologica).

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The vegetation ofthe Comacchio Saltern

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