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Background:Steep environmental gradients, coupled with predicted high temperature rises in the Arctic make arctic mountain vegetation highly suitable for surveillance of changes related to global warming. However, guidelines and baselines for such a purpose are widely lacking since arctic mountain vegetation has been little explored. Aims:We explore options for long-term surveillance on the basis of a detailed analysis of extant plant community patterns and their underlying environmental conditions in the mountainous inland of West Greenland. Methods:Distribution, abundance and site conditions of vegetation types were analysed, using 664 vegetation samples and detailed vegetation maps in four altitudinal belts. Results:Most plant communities had a restricted elevation distribution and were confined to special habitats predominantly defined by mesotopography and soil moisture. Conclusions:Based on the strong linkage to habitat conditions, horizontal and vertical changes of species distribution and vegetation pattern are excellent indicators for inferring underlying environmental changes on three different scales. The recommendations given concerning climate sensitive species and plant communities, ecotones for setting up observation sites as well as stratification of analysis by habitats can be the basis for establishing long-term surveillance programmes on arctic mountain vegetation. [ABSTRACT FROM PUBLISHER]

Plant communities of Unalaska Island in the eastern Aleutian Islands of western Alaska, and their relationship to environmental variables, were studied using a combined Braun-Blanquet and multivariate approach. Seventy relevés represented the range of structural and compositional variation in the matrix of vegetation and landform zonation. Eleven major community types were distinguished within six physiognomic–ecological groups: I. Dry coastal meadows: Honckenya peploides beach meadow, Leymus mollis dune meadow. II. Mesic meadows: Athyrium filix-femina – Aconitum maximum meadow, Athyrium filix-femina – Calamagrostis nutkaensis meadow, Erigeron peregrinus – Thelypteris quelpaertensis meadow. III. Wet snowbed meadow: Carex nigricans snowbed meadow. IV. Heath: Linnaea borealis – Empetrum nigrum heath, Phyllodoce aleutica heath, Vaccinium uliginosum – Thamnolia vermicularis fellfield. V. Mire: Carex pluriflora – Plantago macrocarpa mire. VI. Deciduous shrub thicket: Salix barclayi – Athyrium filix-femina thicket. These were interpreted as a complex gradient primarily influenced by soil moisture, elevation, and pH. Phytogeographical and syntaxonomical analysis of the plant communities indicated that the dry coastal meadows, most of the heaths, and the mire vegetation belonged, respectively, to the widespread classes Honckenyo–Elymetea, Loiseleurio–Vaccinietea, and Scheuchzerio–Caricetea, characterized by their circumpolar and widespread species. Amphi-Beringian species were likely diagnostic of amphi-Beringian syntaxa, many of these yet to be described. Les auteurs ont étudié les communautés végétales de l'île Unalaska dans l'est des îles Aléoutiennes de l'Ouest, ainsi que leurs relations avec les variables environnementales, en utilisant une combinaison des approches de Braun-Blanquet et multivariée. Plusieurs relevés représentent l'amplitude de la variation des structures et de la composition dans le zonage de la matrice de végétation et du paysage. Les auteurs ont identifié 12 types majeurs de communautés dans six groupes écolo-physiognomiques : I. Prairies côtières sèches : prairie côtière à Honckenya peploides, prairie dunaire à Leymus mollis II. Prairies mésiques : prairie à Athyrium filix-femina – Aconitum maximum, prairie à Athyrium filix-femina – Calamagrostis nutkaensis, prairie à Erigeron peregrinus – Thelypteris quelpaertensis; III. Prairies humides à congère de neige à Carex nigricans; IV. ricacaie : éricacaie à Linnaea borealis – Empetrum nigrum, éricacaie à Phyllodoce aleutica, champ d'abattis à Vaccinium uliginosum – Thamnolia vermicularis; V. Tourbière : tourbière à Carex pluriflora – Plantago macrocarpa, et VI. Fourrée arbustive décidue : fourrée à Salix barclayi – Athyrium filix-femina. Les auteurs interprètent ces communautés comme un gradient complexe influencé par l'humidité du sol, l'élévation, et le pH. Les analyses phytogéographiques et syntaxonomiques des communautés végétales indiquent que les prairies côtières, la plupart des éricacaies, et la végétation de tourbière appartiennent respectivement aux classes largement répandues des Honckenyo–Elymetea, Loiseleurio–Vaccinietea et Scheuchzerio–Caricetea, caractérisées par leurs espèces circumpolaires largement répandues. Les espèces amphi-Béringiennes constituent probablement un diagnostic des syntaxons amphi-Béringiens, dont plusieurs restent à décrire. [ABSTRACT FROM AUTHOR]