Abstract
Aims: To clarify the syntaxonomic position of the grasslands in Navarre, with special focus on the dry grasslands, and to characterise the resulting syntaxonomic units in terms of diagnostic species and ecological conditions. Study area: Navarre (northern Spain). Methods: We sampled 119 plots of 10 m2 following the standardised EDGG methodology and analysed them together with 839 plots of similar size recorded in the 1990. For the classification, we used the modified TWINSPAN algorithm, complemented by the determination of diagnostic species with phi coefficients of association, which led to the creation of an expert system. We conducted these steps in a hierarchical manner for each syntaxonomic rank. We visualised the position of the syntaxa along environmental gradients by means of NMDS. Species richness, and structural and ecological characteristics of the syntaxa were compared by ANOVAs. Results: We could clearly identify five phytosociological classes: Lygeo-Stipetea, Festuco-Brometea, Molinio-Arrhenatheretea, Nardetea strictae, and Elyno-Seslerietea. Within the Festuco-Brometea a xeric and a meso-xeric order could be distinguished, with two alliances each, and eight associations in total: Thymelaeo-Aphyllanthetum, Jurineo-Festucetum, Helianthemo-Koelerietum, Prunello-Plantaginetum, Carduncello-Brachypodietum, Helictotricho-Seslerietum, Calamintho-Seselietum and Carici-Teucrietum.Conclusions: The combination of numerical methods allowed a consistent and more objective classification of grassland types in Navarre than previous approaches. At the association level, we could largely reproduce the units previously described with traditional phytosociological methods. By contrast, at higher syntaxonomic level, our analyses suggest significant modifications. Most importantly, a major part of the units traditionally included in the Festuco-Ononidetea seem to fall within the Festuco-Brometea. We could show that bryophytes and lichens are core elements of these grasslands and particularly the Mediterranean ones of Lygeo-Stipetea, both in terms of biodiversity and of diagnostic species. We conclude that the combination of our different numerical methods is promising for deriving more objective and reproducible delimitations of syntaxa in a hierarchical manner. Taxonomic references: Euro+Med (2006–2021) for vascular plants, Hodges et al. (2020) for bryophytes and The British Lichen Society (2021) for lichens, except for Endocarpon loscosii, Heppia lutosa, Psora saviczii and P. vallesiaca, which follow Nimis and Martellos (2021), and Buellia zoharyi, Fulgensia poeltii, Lichenochora clauzadei and Toninia massata, which follow Llimona et al. (2001). Syntaxonomic reference: Mucina et al. (2016), except for those syntaxa specifically treated here and given with authorities. Abbreviations: ANOVA = analysis of variance; EDGG = Eurasian Dry Grassland Group; NMDS: non-metric multidimensional scaling; TWINSPAN = Two-Way Indicator Species Analysis.
Highlights
Grasslands represent one of the most extensive and diverse formations of the world, yet undervalued and under-researched
Since the second half of the 20th century, European grasslands have experienced two extremes of the land-use gradient, and both resulted in the loss of grassland biodiversity (Török and Dengler 2018), which is important in Western Europe, were grasslands are mostly secondary, originating from human land use (Boch et al 2020): (i) intensification of land use or conversion to croplands in productive areas, and (ii) abandonment of marginal lands resulted in the regeneration of forest and shrublands, both processes leading to the loss of grassland-specific biodiversity (Dengler and Tischew 2018)
Our results largely concur with the previous classification of grasslands in Navarre (Berastegi 2013), our analyses suggest a different treatment of the classes Festuco-Brometea, Festuco-Ononidetea and Ononido-Rosmarinetea compared to the Iberian tradition (Rivas-Martínez et al 1991b; Rivas-Martínez 2011)
Summary
Grasslands represent one of the most extensive and diverse formations of the world, yet undervalued and under-researched. Palaearctic grasslands represent the richest habitats for vascular plants at small spatial scales (Dengler et al 2020a). Among the most threatened biomes of the world with the highest proportion of habitat conversion but lowest protection (Hoekstra et al 2005). It is necessary to understand biodiversity patterns of grasslands and how they relate to land use to be able to design conservation and management actions. This understanding requires the harmonisation and standardisation of grassland classification that leads to a consistent syntaxonomy at the European level and will increase the usefulness of vegetation typologies for conservation and management (Willner et al 2017)
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