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Aims: Baltic Sea coastal grasslands are influenced by saline or brackish sea water, a narrow tidal range and non-intensive land use. Since their designation as Natura 2000 habitat types under the EU Habitats Directive, they have become an important conservation issue in Europe. Little supra-regional research has been conducted to date on their floristic and ecological diversity, syntaxonomy and geographic variation. We surveyed the geographical distribution and syntaxonomical variation of saline and brackish grasslands to highlight large-scale gradients in species composition, as well as underlying climatic and other abiotic factors. We discuss the resulting vegetation types in the context of northern Europe and review implications for conservation. Study area: Baltic Sea coast. Methods: We compiled a comprehensive plot-based vegetation dataset for the Baltic Sea coast and subsequently selected relevés by species composition and plot size. We classified 3,732 relevés, using modi­fied TWINSPAN, identified differential species and syntaxa, and performed a DCA with post-hoc fitted intrinsic and climatic variables. We tested main differences in relevant factors for significance. Results: The classification resulted in 33 vegetation types of differing distribution range and area. Most common were the classes Juncetea maritimi and Molinio-Arrhenatheretea, with the classes Phragmito-Magnocaricetea, Cakiletea mari­timae, Saginetea maritimae, Scheuchzerio palustris-Caricetea fuscae and Koelerio-Corynephoretea canescentis also present. Baltic Sea coastal grasslands vary in soil salinity and moisture and, to a lesser extent, in nutrient availability and base content. Conclusions: Variation in the plant communities reflects regional phytogeographical patterns. Communities most similar to north-west European coastal grassland types are characterized by euhaline to a-mesohaline site conditions. Designations of the Natura 2000 habitat types H1330 and H1630 require revision. Many Baltic Sea coastal grassland plant communities include species threatened at the national level. Taxonomic reference: Euro+Med Plantbase (2006-2019), http://ww2.bgbm.org/EuroPlusMed/ [17 January 2019], except for names given in Supplement S3, Table 1. Syntaxonomic reference: Mucina et al. (2016) for higher syntaxa. Abbreviations: BKØ (Belt Sea-Kattegat-Øresund area including the south-western Swedish coast and the German Sea coast); BP (Baltic Proper); BS (Baltic Sea); GeB (German Bight); GB (Great Britain); H (when leading a 4-digit code, European Union Habitats Directive Annex I habitat type); nBS (northern Baltic Sea including the Gulfs of Finland and Bothnia); NL (The Netherlands); var. (variant).

Over the past half century, nature protection in the European Union has been increasingly controlled by commitments to policy and legislative frames, notably the Habitats Directive, originating from the European Union and adopted by an enlarging constituency of member states. Habitat (or biotope) classifications developed in association with these policies, first the Palaearctic habitat classification and CORINE, then the EUNIS habitat classification, have provided typologies with definitions of habitat types intended to aid their recognition, mapping, protection and monitoring. Phytosociological expertise and classifications of formally defined plant communities or syntaxa have played a part in the development of these typologies and in interpretation of the Habitats Directive from the start, though this involvement has been complex and sometimes unclear. This paper catalogues this history and shows how the development of increasingly robust definitions of EUNIS habitat types, an overarching European framework of phytosociological syntaxa and very substantial point-source data (relevés) are converging to aid the interpretation and delivery of environmental policy. In particular, crosswalks between EUNIS habitat types and syntaxa, lists of constant, differential and dominant species, standardised habitat descriptions as well as distribution, predictive and indicative maps are now becoming available. The European Red List of Habitats, also based on the EUNIS typology, provides images and other complementary information on distribution, pressures and threats and a Red List assessment. A comprehensive factsheet with complementary fuller environmental parameterisation for each EUNIS habitat type remains a realistic goal.

WetVegEurope is a research project (http://www.sci.muni.cz/botany/vegsci/wetveg) whose goal is to provide a synthesized formalized classification of the aquatic and marsh vegetation across Europe at the level of phytosociological associations. In order to achieve the project objective, a WetVegEurope database has been created (GIVD ID: EU-00-020, http://www.givd.info/ID/EU-00-020), which currently contains 375,212 vegetation plots of aquatic, marsh and wet vegetation types from 33 European countries. The WetVegEurope database includes datasets from pre-existing national and thematic databases and also 10,616 plots previously not digitalized or even unpublished. This database offers an extensive source of data for future studies on aquatic and marsh plant species and vegetation types at the European scale.

Rubusscrubs belong to the least known and understood vegetation types in Europe. At least in part this is due to the complicated taxonomy and species richness of the main genus in these scrubs. In this study, we explored the regional diversity of Rubusscrubs in the Netherlands. In order to get a clear picture on their species composition free from personal preferences, we used a systematic-randomised sampling scheme to collect data in the three main Rubusregions in the Netherlands along three 100 km long transects. In 185 relevés we recorded 67 known (and three unknown) Rubusspecies. The relevés could be assigned to seven units described in the Dutch national vegetation classification: the Rubetum grati, Rubetum silvatici, Lonicero-Rubion silvatici, Dicrano-Juniperetum, Pruno-Rubetum vestiti, Pruno-Rubion radulae, and the Basal Community Rubus armeniacus. From our study we conclude that the regional variation in Rubusscrubs is substantial, and that only a part of this variation was described in the Dutch national vegetation overview. Especially within the Rubetum silvatici and the Pruno-Rubion radulaeregionally distributed types can be distinguished, which seem to be confined to old landscapes, whereas younger landscapes only harbour common types, or are even devoid of bramble scrubs. The density of relevés made in this study emphasize the importance of bramble scrubs in the landscape of north-western Europe, and we advocate more awareness of the value represented by bramble dominated communities. The vast number of Rubusspecies, many of which having a (very) restricted distribution area, complicate the classification of these scrubs, and can easily lead to the description of countless vegetation types with only a regional distribution. On the other hand, such regionally distributed communities can be of importance for nature conservation because they can harbour rare species, and they add to the regional identity and γ-diversity, and therefore should be recognised at some level.

Aeschimann, D., Lauber, K., Moser, D. M. & Theurillat, J.-P.: Flora alpina. - Ein Atlas sämtlicher 4500 Gefäßpflanzen der Alpen. Mit Farbfotografien von Konrad Lauber und Skizzen von André Michel. - 2670 pp., 5933 colour photographs, 4662 distribution maps, 10 fig., 5 tab., 3 vol. in slipcase 17.5x25 cm, 2004. Haupt Verlag, Bern. ISBN 3-258-06600-0. French edition: Edit. Belin, Paris. ISBN 2-7011-3899-X. Italian edition: Zanichelli ed. Spa, Bologna. ISBN 8808-07159-6. Bastian, O. & Steinhardt, U. (eds.): Development and Perspectives of Landscape Ecology. - 498 pp., 2002. Kluwer Academic Publishers, Dordrecht. ISBN 1-4020-0919-4. Bohn, U. & Neuhäusl, R. with Hettwer, Chr., Gollub, G. & Weber, H.: Karte der natürlichen Vegetation Europas - Map of the Natural Vegetation of Europe. Maßstab/ Scale 1:2 500 000. Part 1: Explanatory Text (in German) with CD-ROM, 656 S. ISBN 3-7843-3837-2. Part 2: Legend (German/English), 153 S. (only in com- bination with part 3). Part 3: Maps, folded (ISBN 3-7843-3809-7) or rolled (ISBN 3-7843-3836-4). 2000/2003. Bundesamt für Naturschutz, Bonn. Federal Agency for Nature Conservation (ed.): Map of the Natural Vegetation of Europe, scale 1:2,500,000. Interactive CD-ROM compiled and revised by U. Bohn, G. Gollub, Ch. Hettwer, Z. Neuhäuslová, Th. Raus, H. Schlüter and H. Weber, technical realisation of the CD-ROM by S. Hennekens. - 2004. Bonn, Germany. BfN-Schriftenvertrieb, Landwirtschaftsverlag Münster, Germany. ISBN 3-7843-3848-8. (Order from: www.lv-h.de/bfn) Gurevitch, J., Scheiner, S. M. & Fox, G. A.: The Ecology of Plants. - 523 pp., 385 illus- trations, 2002. Sinauer Associates, Inc., Publishers. Sunderland, Massachusetts, U.S.A. ISBN 0-87893-291-7. Haacks, M.: Die Küstenvegetation von Neuseeland. Mitteilungen der Geographischen Gesellschaft in Hamburg, Bd. 95. - 269 pp., 77 illustr. & maps, 80 tables, 3 suppl., 2003. Franz Steiner Verlag, Stuttgart. ISBN 3-515-08355-3. Körner, C.: Alpine plant life. Functional plant ecology of high mountain ecosystems. - Second edition, 350 pp., 218 fig., 4 colour plates, 47 tables, 2003. Springer, Berlin, Heidel- berg. ISBN 3-540-00347-9. Lauer, W. & Rafiqpoor, M. D.: Die Klimate der Erde: Eine Klassifikation auf der Grundlage der ökophysiologischen Merkmale der realen Vegetation. - 271 pp., 3 maps, 2002. F. Steiner Verlag, Stuttgart. ISBN 3-515-08072-4. Weber, H. E.: Gebüsche, Hecken, Krautsäume. - In: Pott, R. (Ed.): Ökosysteme Mittel- europas aus geobotanischer Sicht. - 229 pp., 66 colour photos, 28 black-and-white photos, 84 drawings, 54 tables, 2003. Ulmer Verlag, Stuttgart. ISBN 3-8001-4163-9. Härdtle, W., Ewald, J. & Hölzel, N.: Wälder des Tieflandes und der Mittelgebirge. - In: Pott, R. (Ed.): Ökosysteme Mitteleuropas aus geobotanischer Sicht. - 252 pp., 45 colour photos, 65 drawings, 41 tables, 2004. Ulmer Verlag, Stuttgart. ISBN 3-8001-3285-0.

In the development of the Dutch National Vegetation Classification, little emphasis was placed on ordination or gradient analysis. The current study provides a national-scale ordination analysis of salt-marsh communities in the Netherlands and presents it in the context of the National Classification. A series of 4 DCA ordinations derived from synoptic tables of 21 salt-marsh communities, each varying in their emphasis on dominant species, showed that the importance of dominance vs. overall assemblages of species in classifying communities varies with the communities in question: for species-poor communities such as the Spartinetea, T hero-Salicornietea, and portions of the Asteretea tripollii (Puccinellion maritimae and Puccinellio-Spergularion salinae), dominant species were critical in distinguishing communities while for more diverse communities (the Armerion maritimae and the Saginetea maritima of the Astereteae tripolii), total floristic composition was important and over-emphasis on dominant species obscured differences between several communities. Ordination scores were strongly correlated with mean Ellenberg indicator values for salinity and pH, but only weakly with moisture values. In this respect, Ellenberg values do not appear to reflect the critical conditions of duration and timing of flooding in Dutch salt-marsh vegetation. Ordinations based on both synoptic tables and on individual relevés were carried out to study the validity of previously-reported classifications of several related associations. The analysis resolved the question of whether the Suaedetum maritimae is best placed in the Thero-Salicornietea or in the Cakiletea maritimae; it was clearly associated with the Thero-Salicornietea. As for the question of whether certain related associations better belong within the Lolio-Potentillion or within the saltmarsh alliance Armerion maritimae, both options are possible from the point of view of this study. The approach used here of ordinating synoptic tables to locate possible overlap between syntaxa and then using ordinations of individual relevés within these to examine the problem areas further provides a useful method for verifying and revising classifications at the national level.

The nature of the plant community has been a long-standing point of discussion in vegetation science. Already in the early decades of the last century, debate focussed on whether plant communities existed as discrete, intra-dependent entities or merely as loose assemblages of species each responding individualistically to local environmental conditions. Despite the fundamental nature of this question, the issue is generally ignored in many studies. For example, within the study of succession, a major topic in vegetation science, the question of stability within vegetation types is rarely addressed. Generally, succession research investigates vegetation development in terms of communities passing through a series of vegetation types, without considering the nature of these types; they are implicitly regarded to be constant. To some extent, this idea is a misconception, as can be concluded from studies within the framework of the national vegetation classification of the Netherlands. During this program, a large data set has been built up, comprising more than 350,000 vegetation relevés, made in the period 1929-2001. Comparison of sets of relevés from different decades revealed that in most ecosystems the floristic composition of the vegetation types involved has changed, although the appearance of the vegetation and the presence and abundance of - most of - the diagnostic species have remained the same. In the present study, three examples were elucidated: an aquatic vegetation type dominated by Stratiotes aloides (Stratiotetum), a species-rich grassland type on river dunes (Medicagini falcatae-Avenetum pubescentis), and a forest community (Betulo-Quercetum roboris).