Ecologia Mediterranea 2001-27
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ecologia mediterranea Revue Internationale d'Ecologie Méditerranéenne International Journal ofMediterranean Ecology ,, . ' TOME 27 - fascicule 1- 2001 ISSN : 0153-8756 REDACTEUR EN CHEF/ MANAGING EDITOR SECRETARIAT 1SECRETARIAT Frédéric MEDAIL Michelle DOUGNY - Fabrice TRANCHIDA REDACTEURS/EDITORS TRESORIER 1 TREASURER Laurence AFFRE Jacques-Louis de BEAULIEU Philip ROCHE Thierry TATONI Eric VIDAL FONDATEUR 1FOUNDER Prof. Pierre QUÉZEL COMITE DE LECTURE 1ADVISORYBOARD ARONSON J., CEFE CNRS, Montpellier LE FLOC'H E., CEFE CNRS, Montpellier BARBERO M., IMEP, Univ. Aix-Marseille III MARGARIS N. S., Univ. of the Aegan, Mytilène, Grèce BROCK M., Univ. of New England, Armidale, Australie OVALLE c., CSI Quilamapu, INIA, Chili CHEYLAN M., EPHE, Montpellier PEDROTTI F, Univ. degli Studi, Camerino, Italie DEBUSSCHE M., CEFE CNRS, Montpellier PLEGUEZUELOS J. M., Univ. de Grenade, Espagne FADY B., INRA, Avignon PONEL P., IMEP, CNRS, Marseille GOODFRIEND G. A., Carnegie Inst. Washington, USA PRODON R., Labo. Arago, Univ. P. M. Curie, Paris VI GRILLAS P., Station Biologique Tour du Valat, Arles RICHARDSON O. M., Univ.Cape Town, Afrique du Sud GurOT J., IMEP, CNRS, Marseille SANS F X., Univ. de Barcelone, Espagne HOBBS R. J., CSIRO, Midland, Australie SHMIDA A., Hebrew Univ. of Jerusalem, Israël KREITER S., ENSA-M INRA, Montpellier URBINATI C., AgripoIis, Legnaro, Italie ecologia mediterranea Faculté des Sciences et Techniques de Saint Jérôme Institut Méditerranéen d'Ecologie et de Paléoécologie, case 461 F- 13397 MARSEILLE Cedex 20 FRANCE Tél. : + 33 4 91 28 85 35 - Fax: + 33 4 91 28 80 51 E-mail: [email protected] URL: http://www.ecologia.fst.u-3mrs.fr Abonnements 1Subscription Un an =deux numéros / one year =two issues: France: 400 F + 60 F de frais de port Europe: 400 F + 80 F de frais de port Amérique, Afrique, Asie: 400 F + 120 F de frais de port Tous les fascicules de la revue sont disponibles. Pour les commander et pour tout renseignement, nous contacter à l'adresse ci-dessus. Ail issues are available. To order or to obtain information, please contact the address above. ec%gia mediterranea 27 (/), J5-32 - 200/ Vegetation-environment relationships in Lefka Ori (Crete, Greece): ordination results from montane-mediterranean and oro mediterranean communities Relations végétation-environnement dans le massif des Lefka Ori (Crète, Grèce) : résultats d'une ordination des communautés des étages montagnard-méditerranéen et oro-mediterranéen LN, Vogiatzakis & G.H.Griffiths Dcpartment of Geography, The University of Reading, Whiteknights, Reading, UK. RG6 6AB. Tel. +44 118 9318733, Email: i. [email protected] ABSTRACT The extensive Lefka Ori massif on the island of Crete supports more than 100 endemic plant species and is of considerable ecological importance internationally. However, little is known or understood about plant community distribution in the massif. Montane-mediterranean and oro-mediterranean vegetation was sampled at two study sites and the relationships betwccn a range of environmental variables and plant community distribution were investigated. Classification of the t10ristic data was performed with Two Way Indicator Species Analysis (TWINSPAN) resulting in five distinct vegetation communities. Canonical Correspondence Analysis (CCA) suggested that the two main compositional gradients were associated with altitude, pH, organic matter and slope. Rocky slopes, screes and karstic depressions were identified from field observations as the main habitats. Separate ordination analysis was performed only for the first two groups since the third supported only one community. Altitude and bare rock percent cover control vegetation patterns on rocky slopes, whereas on screes ground cover and pH are the most important factors. Key-words: ordination, Lefka Ori, endemic plants, conservation RESUME L'imposant massif montagneux des Lefka Ori sur l'île de Crète (Grèce), abrite plus d'une centaine de plantes endémiques. L'importance de cette richesse tloristique et écologique est reconnue à l'échelle mondiale. Cependant, peu de choses sont connues en ce qui concerne la distribution des communautés végétales dans ce massif. Des relevés de végétation ont été réalisés sur deux sites d'étude, au niveau des étages montagnard-méditerranéen ct oro-meditérranéen, dans le but d'étudier l'int1uence possible de plusieurs variables environnementales sur la distribution des communautés. Une classification des données t10ristiques a été établie à l'aide du logiciel TWINSPAN, et a permis de définir cinq communautés de végétation distinctes. Une analyse canonique des correspondances (ACC) indique que les deux principaux gradients de composition t10ristique sont associés à l'altitude, au pH, à la matière organique et à la pente. Les observations de terrain ont permis d'identifier comme principaux habitats, les pentes rocheuses, les éboulis, et les dolines. Une analyse d'ordination séparée a été menée uniquement sur les deux premiers groupes, car le troisième ne comptait qu'une seule communauté. Sur les pentes rocheuses, l'altitude et le pourcentage de la roche nue déterminent le type de couverture végétale. Par contre, sur les éboulis, la couverture du sol ainsi que le pH constituent les paramètres les plus importants dans la détermination du couvert végétal. Mots-clés: ordination, Lefka Ori, plantes endémiques, conservation Vogiatzakis et al. Vegetation-environment relationships in Lefka Ori (Crete, Greece) INTRODUCTION Worldwide, the destruction of natural habitats or include Crete within one of the Centres of Plant their conversion to other uses is resuIting in rapid Diversity where immediate conservation action is species loss. From an estimated global total of suggested. According to Delanoë et al. (1996), Il 270,000 plant species, 12.5 percent are considered to percent of the island's species belong to globally be threatened (Walter & Gillet, 1998). The expansion threatened taxa, while 13 percent of the total taxa are of forestry and agriculture, habitat loss and locally threatened (Table 1). fragmentation, soil and water pollution and global c1imate change are ail contributing to the destruction Despite the importance of the Cretan flora in a of habitats and the loss of plant species. Despite the regional and global context, human modification of severity of the problem a recent IUCN report (Walter both natural and cultural landscapes continues to & Gillet. 1998) stresses that there is insufficient threaten the survival of endemic species on the island. knowledge of the taxonomy, habitat requirements and According to Grove & Rackham (1993), these threats distribution of many plants to identify potential are: tourism. urbanisation, road building, threats, and therefore, to assess their vulnerability to intensification of cultivation, changes in grazing extinction. pressure, abandonment of cultivation, the increase in tree coyer and increased fire frequency. These prablems are particularly weil illustrated by the situation in the Mediterranean Basin, despite its Although knowledge of the taxonomy of the recognition as a reservoir of plant biodiversity Cretan flora is considered to be satisfactory, the (Gomez-Campo, 1985; Heywood, 1995; Médail & understanding of species ecology and distribution is Quézel, 1997). In recent decades, agricultural relatively POOf. The most important sources of intensification, overgrazing, afforestation and tourist distribution data for the Cretan flora can be found in development have destrayed and continue to threaten Turland et al. (1993), ChiIton & Turland (1997), Strid important habitats and their associated plants. The (1986), Strid & Tan (1991) and Jalas & Suominen present extinction rate of the Mediterranean higher (1972-1996). There are also numerous publications on plants is 0.15 percent of the total, representing 37 individual Cretan species (e.g. Greuter et al., 1985). species presumed to be extinct. Moreover, there are AlI these sources use different mapping schemes, 4251 plant taxa under threat in the Mediterranean making comparisons between species' distributions (Greuter, 1994). from different sources difficult. There is only one National Park on the island, the Samaria Gorge. The Conflict between development pressures and Samaria Park is 48.5km' in area and contains stands of conservation pnontles is a major problem in many pine-cypress forest and associated endemic species. parts of the world but is particularly acute on the The islands of Dia and Theodorou to the north of island of Crete. The varied topography, geology and Iraklion and Chania respectively are Nature Reserves. climate of the island give rise to a wide variety of These are managed mainly for the population of the ecological niches; this is reflected, in tum, in a diverse Cretan ibex, an endemic mammal transferred from flora. The island contains 1706 native plant species Samaria. Along a coastal valley at Vai in the N.E. of (Turland et al., 1993), of which 180 (species and the island, the largest Cretan date palms (Phoenix subspecies) are wholly or mainly confined to Crete theophrastii Greuter) are protected and monitored by (Montmollin & Iatrou, 1995). Crete, therefore, is a the Forest Service. At least 30 sites in Crete have also place of considerable ecological and botanical interest. been proposed for inclusion in the NATURA 2000 This is retlected in various phytosociological (Zohary network of protected sites within the European Union & Orshan, 1965; Barbera & Quézel, 1980; Zaffran, (Council of Europe,