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Grasslands of Navarre (Spain), focusing on the Festuco-Brometea: classification, hierarchical expert system and characterisation
expand article infoItziar García-Mijangos, Asun Berastegi§, Idoia Biurrun, Iwona Dembicz|, Monika Janišová, Anna Kuzemko#, Denys Vynokurov#, Didem Ambarlı¤, Javier Etayo«, Goffredo Filibeck», Ute Jandt˄, Rayna Natcheva˅, Oktay Yildiz¤, Jürgen Dengler¦ˀˁ
‡ University of the Basque Country, Bilbao, Spain
§ Environmental Management of Navarre, Pamplona-Iruña, Spain
| University of Warsaw, Warsaw, Poland
¶ Institute of Botany, Plant Science and Biodiversity Center, Slovak Academy of Sciences, Banská Bystrica, Slovakia
# M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, Kyiv, Ukraine
¤ Düzce University, Düzce, Turkey
« I.E.S. Zizur Institute, Pamplona, Spain
» University of Tuscia, Viterbo, Italy
˄ Martin Luther University Halle-Wittenberg, Halle, Germany
˅ Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria
¦ Zurich University of Applied Sciences, Wädenswil, Switzerland
ˀ University of Bayreuth, Bayreuth, Germany
ˁ German Centre for Integrative Biodiversity Research, Leipzig, Germany
Open Access

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.

Keywords

diagnostic species, electronic expert system, Elyno-Seslerietea, Festuco-Brometea, Festuco-Ononidetea, grassland, Lygeo-Stipetea, modified TWINSPAN, Molinio-Arrhenatheretea, Nardetea strictae, Navarre, vegetation classification

Introduction

Grasslands represent one of the most extensive and diverse formations of the world, yet undervalued and under-researched. Grasslands are spontaneously occurring herbaceous vegetation types that are mostly dominated by grasses (Poaceae) or other graminoids (Cyperaceae, Juncaceae) and have a relatively high herb-layer cover (usually > 10%), while woody species (dwarf shrubs, shrubs and trees), if present at all, have a significantly lower cover than the herbs (Dengler et al. 2020a). Extending in all continents except Antarctica, grasslands host thousands of habitat specialist species, support agricultural production, people’s livelihoods based on traditional and indigenous lifestyles, and several other ecosystem services such as pollination for crops and water regulation (Bengtsson et al. 2019). Palaearctic grasslands represent the richest habitats for vascular plants at small spatial scales (Dengler et al. 2020a). Temperate grasslands are, however, among the most threatened biomes of the world with the highest proportion of habitat conversion but lowest protection (Hoekstra et al. 2005).

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 specifically 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). 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 therefore, then will increase the usefulness of vegetation typologies for conservation and management (Willner et al. 2017).

During the last decades, a great effort on grassland classification has been made, based on large vegetation-plot databases and numerical analysis in several countries or regions across Europe to delimit and define the different syntaxonomic units. Several studies have been developed at a regional, up to continental scale on dry-grasslands (Illyés et al. 2007; Vassilev et al. 2012; Aćić et al. 2015) or mesic and wet grasslands (Kuzemko 2016; Rodríguez-Rojo et al. 2017; Škvorc et al. 2020). The broadest studies regarding syntaxonomic scope and geographic extent are focused on dry and semi-dry grasslands (Willner et al. 2017, 2019). As a result, great advances to define the classes Festuco-Brometea, Molinio-Arrhenatheretea, Nardetea strictae and Koelerio-Corynephoretea in temperate Europe have been made. However, grasslands of Southern Europe are still not well-known and the distinction of the Mediterranean grasslands from those of temperate Europe is not clear, especially along the submediterranean areas that, although broadly classified as temperate, still exhibit the “Mediterranean” sharp drop in summer precipitation levels (Apostolova et al. 2014; Aćić et al. 2015).

Phytosociological studies in the Iberian Peninsula have been broadly developed in the last century and were synthesized in the syntaxonomic checklist of Spain (Rivas-Martínez 2011). More recently, some reviews based on large vegetation databases aimed to obtain a consistent grassland classification (Rodríguez-Rojo and Fernández-González 2014; Rodríguez-Rojo et al. 2014; García-Madrid et al. 2016; Gavilán et al. 2017). Nevertheless, there is a lack of studies on the typical Mediterranean grassland and low scrub classes Festuco hystricis-Ononidetea striatae, Ononido-Rosmarinetea and Lygeo sparti-Stipetea tenacissimae (but see Marcenò et al. 2019). Moreover, in the submediterranean areas, these Mediterranean grasslands are in touch (across elevational or edaphic gradients) with temperate grasslands placed in the class Festuco-Brometea, but their boundaries are not clearly defined (Cancellieri et al. 2020). Studies of such transitional areas are necessary to discriminate between different grassland types and define the diagnostic species that differentiate these classes.

Navarre region, located in northern Iberian Peninsula, is a bioclimatically diverse region where Alpine, Atlantic and Mediterranean biogeographical areas converge. The long history of grazing and management throughout the area has resulted in the broad spread of grasslands. The region has an important elevational and precipitation gradient that allows the coexistence of dry and mesic grasslands as well as alpine and Mediterranean semi-arid communities (Berastegi 2013). This makes this region very suitable for studying the diversity of grassland communities that are driven by ecological and management gradients. Navarre is also an interesting area for the challenge of drawing the boundaries between the temperate and Mediterranean grasslands and establishing their valid classification. Many phytosociological studies have been carried out in Navarran grasslands (Darquistade et al. 2004; Berastegi et al. 2005; Berastegi et al. 2010; Berastegi 2013). Nevertheless, only a few of these studies have applied numerical methods (Peralta and Olano 2001), and none of them included bryophytes and lichens, although these taxonomic groups may become an important component of several grassland types (Biurrun et al. 2021).

According to Berastegi (2013), 69 grassland associations or communities can be recognised in Navarre, grouped in 32 alliances and 11 phytosociological classes. In the high-elevation areas of Pyrenees, communities of Carici rupestris-Kobresietea bellardii, Juncetea trifidi, and Elyno-Seslerietea coexist; in the temperate zone, grasslands of Nardetea strictae, Sedo-Scleranthetea, Molinio-Arrhenetheretea and Festuco-Brometea, and in Mediterranean areas communities of Festuco-Ononidetea, Lygeo-Stipetea, Poetea bulbosae and Stipo-Trachynietea (Berastegi 2013). Although some of these classes are well defined floristically and biogeographically, those occurring in submediterranean areas need clarification as many species of different floristic origin coexist in the same area. In these cases, the occurrence of temperate or Mediterranean grasslands is driven by edaphic and microclimatic conditions. There are also some interpretation issues, such as the inclusion of some Mediterranean communities in Festuco-Ononidetea or Ononido-Rosmarinetea (Berastegi et al. 2005; Berastegi 2013). All this led to the organisation of the 7th Field Workshop (Biurrun et al. 2014) to sample by means of biodiversity plots (Dengler et al. 2016a) all types of grasslands along latitudinal and elevational gradients. The expedition ran from subalpine areas in Pyrenees to semi-arid Mediterranean ones where information on bryophytes and lichens as well as vascular plants was recorded.

The high grassland diversity in Navarre reflects the richness of grassland habitats of interest for European Community (European Commission 2013). Regarding the habitat types included in the Annex I of the Habitat Directive, nine of those belonging to natural and semi-natural grassland formations are present in Navarre (Peralta et al. 2018). Phytosociological classifications of formally defined syntaxa were also used to interpret the types in the Habitats Directive, so determining diagnostic species for different types of grassland is necessary to interpret the habitats and to assess their conservation status (Tsiripidis et al. 2018). However, the definition of these habitats is sometimes ambiguous and there are still some inconsistent interpretations between countries and regions, which impede effective conservation of grasslands habitats (Evans 2013). Rodriguez-Rojo et al. (2020) aimed to develop an expert system for semi-natural grassland habitat identification through the analysis of their characteristic species, but Mediterranean grasslands were not included in the analysis. The delimitation and definition of diagnostic species of the Mediterranean grassland classes would help to properly interpret the habitat types that would lead to their adequate management and protection.

The large amount of data available related to grassland in the region of Navarre and its strategic geographical position where different climatic conditions converge provide a unique opportunity to clarify grassland syntaxonomy, especially those from submediterranean areas. More specifically, we aim to 1) Identify the main grassland types in Navarre using numerical and reproducible methods, 2) Compare our results with existing traditional classifications at the level of alliance or association 3) Define the diagnostic species of syntaxa including bryophytes and lichens. 4) Characterise and differentiate associations with regard to topographic, edaphic and climatic variables.

Study area

Navarre is a territory of 10,391 km2 located in the north-central part of the Iberian Peninsula. There is a wide elevational range in the region, from 25 m a.s.l. in Endarlatsa, 15 km from the Cantabrian Sea in the north, to 2,466 m a.s.l. in the Mesa de los Tres Reyes in the western Pyrenees. The bioclimate is temperate in the northern part of the region, and Mediterranean in the south, with large submediterranean areas in the central part (Loidi and Báscones 2006; Peralta et al. 2018). As regards the thermic and humidity types proposed in the bioclimatic classification of Rivas-Martínez (Rivas-Martínez 1996), mesotemperate (colline), supratemperate (montane), orotemperate (subalpine) and cryorotemperate (alpine) thermotypes can be distinguished in the temperate zone, while in the Mediterranean areas only the mesomediterranean and the supramediterranean occur. There is a high ombrotype diversity, from the semiarid in the Ebro valley to the ultrahyperhumid in the northern mountains (Peralta et al. 2018). The temperate-climate area is included in the Atlantic and Alpine regions. The western part has a stronger Atlantic influence (Atlantic region) while the eastern area is more influenced by the Pyrenees (Alpine region). The Mediterrranean-climate area is included in the Mediterranean region.

Several types of deciduous forests prevail in the temperate zone, where secondary grasslands, mainly mesic and meso-xeric grasslands, are an important component of the landscape. Sclerophyllous woodlands dominate in the Mediterranean areas of southern Navarre, with Mediterranean grasslands and garrigues as secondary vegetation. In the Pyrenees, alpine grasslands and scrubs occur above 1,700 m a.s.l., in the subalpine belt mostly as secondary vegetation replacing Pinus uncinata woodlands, and as potential natural vegetation in the alpine belt, above ca. 2,100 m a.s.l. (Loidi and Báscones 2006).

Geological diversity also has a great influence on the vegetation. Shales, quartzites or granites from the Palaeozoic are common in the northern area of Navarre, mostly in the Atlantic region. Red sandstones and conglomerates from the Triassic surround these Palaeozoic rocks. Limestones, marls and dolomites from the Jurassic and Cretaceous period, and also limestones, marls, flysch substrates, but also calcarenites from the continental Tertiary are dominant in all of the central area of Navarre. From the continental Tertiary, sandstones, clays, slimes, but also limestones and gypsum are dominant in the south of Navarre, mostly in the Mediterranean region (Del Valle Lersundi et al. 1997).

Methods

Vegetation data

We took 119 10-m² plots sampled following the standard EDGG methodology (Dengler et al. 2016a) during the EDGG Field Workshop in Navarre, between 16th and 23rd of June 2014 (Biurrun et al. 2014). The sampling focused on dry and semi-dry grasslands but covered the full climatic/elevation gradient in the region. All vascular plants as well and terricolous bryophytes and lichens, and their percentage cover were recorded. Additionally, an extensive set of structural and site variables were recorded (for all available variables and the underlying methodology, see Suppl. material 1).

Furthermore, we included those 839 vegetation plots from Berastegi (2013), recorded between 1996 and 1999, that had a plot size between 5 and 25 m². We excluded smaller and larger plots because otherwise serious distortion of species constancies and fidelities would be expected (Dengler et al. 2009). In these plots, only vascular plants were recorded, with a 7-step variant of the Braun-Blanquet scale (Braun-Blanquet 1932). Apart from coordinates and elevation, no other structural or site variables are available for these data.

Although these plots from the additional dataset were evenly distributed across the region and all grassland types, we wish to highlight that four of the 11 classes represented in Berastegi (2013) were only documented by fewer than 10 relevés. Two of them normally occur as small patches in mosaics with grasslands of other classes (Stipo-Trachynietea and Poetea bulbosae) and the other two are very rare in Navarre (Carici-Kobresietea and Caricetea curvulae). Another important aspect of this dataset is that the classes Festuco-Ononidetea and Ononido-Rosmarinetea have been only partially included. The former one encompasses oro- and supramediterranean grasslands and shrublands (Mucina et al. 2016), but Berastegi (2013) only considered the dry grasslands of the associations Carici-Teucrietum pyrenaici, Helianthemo-Koelerietum vallesianae and Helictotricho-Seslerietum hispanicae from the order Ononidetalia striatae (and thus excluded dwarf-shrub communities), and those belonging to the order Festuco-Poetalia. The Ononido-Rosmarinetea, and specifically the order Rosmarinetalia, are defined as Mediterranean scrub (tomillar, espleguer, romeral, garrigue) on base-rich substrates (Mucina et al. 2016). In this study we only considered the association Thymelaeo-Aphyllanthetum monspeliensis, described from the central part of Navarre (Braun-Blanquet 1966) and characterised by dwarf chamaephytes of the genera Thymus, Helianthemum, Fumana and Teucrium among others. Berastegi (2013) only sampled stands of the subassociation brachypodietosum retusi, dominated by hard-leaved grasses (Brachypodium retusum, Helictochloa bromoides) and other hemicryptophytes such as Bromopsis erecta subsp. erecta, Carex humilis, Helictochloa pratensis subsp. iberica, Sanguisorba minor aggr. and Carex flacca subsp. flacca.

The combination of both datasets resulted in a total of 958 vegetation plots. The data from EDGG expedition are stored in and available from the GrassPlot database (Dengler et al. 2018a; Biurrun et al. 2019; https://edgg.org/databases/GrassPlot) as dataset ES_A. The data from Berastegi (2013) are stored in the Vegetation-Plot Database of the University of the Basque Country (BIOVEG) (Biurrun et al. 2012), which is available in the European Vegetation Archive (Chytrý et al. 2016) and the Global Vegetation Database sPlot (Bruelheide et al. 2019) as dataset EU-00-011. All plots are provided in Suppl. materials 1 (header data) and 2 (composition data).

Soil analyses

Soil samples were collected in each EDGG plot. Samples were taken with a hand shovel from the uppermost 5–10 cm at five random points within the plot, merged in a mixed sample and air-dried. The coarse fragment of the samples was determined by dry screening (Ø > 2 mm) and soil texture was determined by the Bouyoucos hydrometer method (Gee and Bauder 1986). The acidity and electrical conductivity (EC) were determined in air-dried soil samples dissolved in pure water using pH meter and EC meter (Thomas 1996). Lime content was determined by a Scheibler calcimeter. Soil organic matter content was determined by Walkley-Black wet combustion.

Climatic data

We retrieved climatic data from CHELSA dataset version 1.2 (Karger et al. 2017) at 30 arc sec resolution. As climatic parameters, we selected mean annual temperature, annual precipitation and Mediterranity Index: Med = Eva / Prec, where Eva is mean potential evapotranspiration during summer months, and Prec is sum of precipitation during the summer months (Rivas-Martínez 1996).

Data preparation for classification analyses

Before numerical analysis, we unified species taxonomy and nomenclature. Vascular plants were named according to Euro+Med PlantBase (Euro+Med 2006–2021), bryophytes according to Hodges et al. (2020) and lichens according to The British Lichen Society (2021), with the exception of those taxa not included there: Endocarpon loscosii, Heppia lutosa, Psora saviczii and P. vallesiaca follow Nimis and Martellos (2021), while Buellia zoharyi, Fulgensia poeltii, Lichenochora clauzadei and Toninia massata follow Llimona et al. (2001). We merged several groups of closely related species that cannot always be determined to species level into aggregates (aggr.), whose definitions are provided in Suppl. material 3. Species recognised only at the genus level were deleted, and subspecies that were not always recognised by the authors were combined into species. Bryophytes and lichens were removed for the initial unsupervised classification, but re-integrated later (see below) since they were only recorded in a subset of relevés.

Numerical classification and expert system development

For the initial unsupervised classifications, we used the modified version of TWINSPAN (Roleček et al. 2009) implemented in JUICE (Tichý 2002) with the three pseudospecies cut levels at 0%, 5% and 15%, and average Sørensen dissimilarity as a measure of cluster heterogeneity. Species with only one occurrence were excluded. TWINSPAN analysis resulted in ten groups as the best solution that corresponded very closely to the phytosociological classes of grasslands represented in the study area according to a previous study (Berastegi 2013).

In the case of very large datasets, classification is highly dependent on the selection of attributes (species) used. The more attributes used, the data become more scattered (Visa et al. 2011). In this context, the selection of diagnostic species that can be used in the classification of vegetation is one of the challenges to be addressed. Here we used confusion matrices to select relevés that matched both supervised and unsupervised classifications for subsequent selection of diagnostic species. These species were used for further classification (expert system) of the entire dataset, so that misclassified relevés were reorganised appropriately.

We created the confusion matrix comparing the original (expert-based) and new numerical (unsupervised) classifications (see Suppl. material 4). We selected those relevés that were consistently classified in both approaches as a sort of consensus core of the respective vegetation units. Based on these plots (n = 639), we determined the diagnostic species for the classes (see below). The list of diagnostic species was then translated into an expert system implemented in JUICE (Tichý 2002), with the principle that each plot is assigned to the class whose diagnostic species prevail, based on the sum of square root transformed cover values (as for example widely implemented in Chytrý et al. (2020)). This approach in its current implementation in JUICE leaves a few plots unassigned if they have exactly the same score of diagnostic species for two classes. After applying the so-developed expert system to the whole dataset, we then determined the diagnostic species of the resulting classes again.

In the case of the classes, we found that three of the traditional classes shared a significant number of frequent species and therefore, we decided to merge them and re-run the previous steps to achieve the final expert system and the final set of diagnostic species of classes. We continued then, with the same approach, with our main target class Festuco-Brometea to search for the most plausible division into orders. Criteria were based on how well the resulting units were floristically and ecologically characterised and how closely they matched the general syntaxonomic system of Europe. Next, we continued in each of the resulting orders to find an appropriate division into alliances and finally for each of the alliances we analysed the appropriate subdivision into associations separately. For each syntaxonomic level and cluster we therefore followed the procedure of: (1) running modified TWINSPAN, (2) identifying a reasonable number of syntaxa of the next lower level and (3) determining their diagnostic species. In the case of order and alliance we selected the relevés that matched both the expert and TWINSPAN classification, but for associations we used only the TWINSPAN results, (4) translating these into an expert system, (5) appling this expert system to the data including the type relevés of all associations included in Festuco-Brometea (details provided in Suppl. material 5) and (6) re-determining the diagnostic species based on the group assignment resulting from the expert system. Accordingly, we can then present a hierarchical expert system in JUICE syntax that allows the standardised reproduction of our classification and its application on new relevés (Suppl. material 612).

We followed the fourth edition of the International Code of Phytosociological Nomenclature (ICPN; Theurillat et al. 2021) for the nomenclature of plant communities.

We determined diagnostic species using the phi coefficient of association (Chytrý et al. 2002) standardised to equal plot number per cluster (Tichý and Chytrý 2006). We also determined the diagnostic species in a hierarchical fashion, corresponding to the hierarchical nature of syntaxonomy (Dengler et al. 2008; Theurillat et al. 2021) and to our hierarchical expert system. Since this approach is not implemented in JUICE (Tichý 2002) thus far, we carried out all calculations in Microsoft Excel, which also allowed the production of formatted tables. We acknowledge that this approach has the potential shortcoming of not being able to filter for statistical significance with Fisher’s exact test as is possible in JUICE. However, given the relatively large number of plots per unit and the relatively high thresholds for phi that we applied, the number of non-significant diagnostic species should be negligible. We considered species as diagnostic when phi ≥ 0.25 and as highly diagnostic when phi ≥ 0.5. While phi-values refer to the concentration of a species in one syntaxon compared to the rest of the dataset as a whole, in fact the syntaxonomically relevant aspect is the comparison to the syntaxon of the same rank where the species reaches the next-higher constancy/fidelity (see Dengler 2003; Dengler et al. 2005, 2018b; Tsiripidis et al. 2009). Therefore, for species to be considered diagnostic, we also required that their phi-value was at least 0.25 higher than in the syntaxon of the same rank with the next-higher phi-value. If all syntaxa of a certain rank were ordered by decreasing phi-values of a certain species, the species was considered diagnostic for the first syntaxa prior to a decrease in phi-values ≥ 0.25. If no such decrease occurred or if the maximum phi-value was below 0.25, the species was not considered diagnostic anywhere. We applied these calculations for all four syntaxonomic levels and identified a species as diagnostic to the level where it reached its maximum phi-value, provided all aforementioned criteria were fulfilled. Last but not least, we also determined diagnostic species for the bryophytes and lichens, which had not been used in the set-up of the system, by adding their data again post-hoc. Importantly, here the constancy values were calculated based on the smaller sample of plots from the EDGG Field Workshop only, but otherwise in the same way.

NMDS ordination

To visualize the gradient of vascular plant species composition across the vegetation types, we used non-metric multidimensional scaling (NMDS; McCune and Grace 2002) calculated in the Canoco 5 software (ter Braak and Šmilauer 2012). Prior to the calculation, the Braun-Blanquet scale was transformed to mean percentage cover values. Bray-Curtis dissimilarity was calculated on the log-transformed cover of each vascular plant species in each plot. The sample configuration from non-metric multidimensional scaling (NMDS) was centred and rotated by principal component analysis. Elevation and three bioclimatic variables (mean annual temperature, annual precipitation and Mediterraneity Index) were used as supplementary variables. The whole data set (containing 958 samples) as well as the data subset of relevés included in the Festuco-Brometea (containing 339 samples) were analysed.

Analyses of differences between syntaxa

Differences among classes regarding structural, topographic, bioclimatic and soil variables, as well as regarding richness values, were analysed by means of analyses of variance (ANOVAs) in the R programming language (R Core Team 2021). The same was done with the Festuco-Brometea subset to compare associations and alliances. Tukey’s post-hoc test was applied following a significant ANOVA (p < 0.05). We checked whether the assumptions of linear models (homoscedasticity and normality of residuals) were severely violated by visual inspection of the boxplots, and since this was not the case, we stuck to the linear model (ANOVA) (see Quinn and Keough 2002).

Results

Subdivision of all grasslands into classes

At the level of ten groups, the TWINSPAN analysis resulted in a division of the data where the classification into seven classes proposed by Berastegi (2013) can be recognised to a large extent (Figure 1). We then reduced the hierarchy of these groups into eight clusters. Clusters 1 and 2 were related to Elyno-Seslerietea and Festuco-Ononidetea classes, respectively. Cluster 3 grouped relevés from Lygeo-Stipetea and Stipo-Trachynietea classes. Cluster 4 was composed mostly of the relevés of the association Elytrigio campestris-Brachypodietum phoenicoidis, traditionally assigned to the order Brachypodietalia phoenicoidis in Festuco-Brometea. Clusters 5 and 6 were related to Ononido-Rosmarinetea and Festuco-Brometea, respectively. Groups 7, 8 and 9 corresponded to three orders of Molinio-Arrhenatheretea (Holoschoenetalia, Molinietalia and Arrhenatheretalia), so we grouped them in Cluster 7. Cluster 8 grouped relevés belonging to the classes Nardetea strictae and Sedo-Scleranthetea.

Figure 1. 

Dendogram of the modified TWINSPAN classification of the 958 grassland relevés from Navarre into ten groups gathered in eight clusters.

The synoptic table with the diagnostic species for each cluster of the modified TWINSPAN analysis is presented in Suppl. material 13 (cluster 4 was not considered as it was related only to one association). In this table, we can see that the relevés in clusters 2 and 5 related to the classes Festuco-Ononidetea and Ononido-Rosmarinetea presented many diagnostic species considered characteristic of Festuco-Brometea (Bromopsis erecta subsp. erecta, Carex humilis, Carthamus mitissimus, Potentilla tabernaemontani). Therefore, these two groups were joined to cluster 6, related to the Festuco-Brometea, for subsequent analyses. We finally recognised five groups corresponding to the following classes of grasslands in Navarre: LYG (Lygeo-Stipetea), FES (Festuco-Brometea), MOL (Molinio-Arrhenatheretea), NAR (Nardetea strictae) and SES (Elyno-Seslerietea).

The relationship between the previous expert-based classification (Berastegi 2013) and our classification of five classes based on the expert system analysis is displayed in Table 1. The proportion of relevés matching in both classifications (in brackets) ranged between 60 and 100%. In FES the expert system gathered most of the relevés previously classified in Festuco-Brometea, Festuco-Ononidetea and Ononido-Rosmarineta. However, 35% of relevés previously classified in Festuco-Brometea were distributed among MOL and NAR. From the class Festuco-Ononidetea 23% relevés were classified in SES and 13% relevés from Ononido-Rosmarinetea were included into LYG. Only eight relevés (0,8%) remained unclassified.

Table 1.

Relationship between the original classification and the expert system classification. In each column the number of relevés and the proportion related to the total of relevés belonging to the original classification (in brackets) that match the expert system are shown.

Syntaxonomic classes (original classification) Expert System classification Nº rel. per class
LYG (%) FES (%) MOL (%) NAR (%) SES (%) Non-classified
Lygeo–Stipetea 25 (96) 1 (4) 26
Stipo–Trachynietea 10 (100) 10
Ononido–Rosmarinetea 5 (13) 33 (87) 38
Festuco–Brometea 8 (4) 131 (61) 34 (16) 40 (19) 2 215
Festuco–Ononidetea 158 (75) 1 (< 1) 2 (1) 48 (23) 1 210
Molinio–Arrhenatheretea 13 (6) 185 (86) 17 (8) 1 216
Nardetea strictae 149 (96) 5 (3) 1 155
Sedo–Scleranthetea 11 (85) 1 (8) 1 13
Elyno–Seslerietea 1 (2) 3 (5) 58 (93) 2 64
Carici–Kobresietea 2 2
Caricetea curvulae 1 1
Poetea bulbosae 6 2 8
Nº relevés per group 54 339 220 223 114 8 958

LYG – Lygeo-Stipetea (Figure 2D)

The expert system analysis included in this group LYG most relevés that were originally classified in the class Lygeo-Stipetea. Communities dominated by therophytes of Stipo-Trachynietea and those from Poetea bulbosae were also classified in this group, as they shared many annual species: Bombycilaena erecta, Catapodium rigidum, Linum strictum, Trachynia distachya, etc. LYG also includes some relevés from the subassociation Thymelaeo-Aphyllanthetum brachypodietosum retusi of the class Ononido-Rosmarinetea and from the association Elytrigio campestris-Brachypodietum phoenicoidis of Festuco-Brometea.

Figure 2. 

Photo plate showing typical stands of four of the five distinguished vegetation classes (for Festuco-Brometea, see Figures 1314). A Elyno-Seslerietea, A1 Primula intricata, A2 Festuca gautieri subsp. scoparia; B Nardetea strictae (Nardus stricta, Trifolium alpinum, Lotus alpinus, Jasione laevis subsp. laevis); C Molinio-Arrhenatheretea; D Lygeo-Stipetea (Lygeum spartum). Photos: J. Dengler (A1, A2, B); A. Berastegi (C); Renaud Jaunatre (D).

These communities are characterised by the presence of hard-leaved grasses such as Brachypodium retusum, Helictochloa bromoides, Lygeum spartum and Stipa parviflora and dwarf chamaephytes as well as many therophytes (Table 2). They are distributed throughout the southern part of Navarre, with a typical Mediterranean climate, although they also occur in the lower elevations of the central area, always in the mesomediterranean thermotype (Figure 3).

Table 2.

Abridged constancy table of the five grassland classes considered in this study. Values are percentage constancies, and species are ordered by decreasing phi-values in the respective syntaxon, respectively by decreasing overall constancy for non-diagnostic species. In the upper part vascular plants are given, in the lower part bryophytes and lichens, whose constancies and fidelities have been calculated based only on the plots of the EDGG Field Workshop. In the table, the 15 vascular plant taxa and the eight non-vascular plant taxa with the highest fidelity in a class are shown, plus all taxa that are diagnostic for multiple classes and all taxa with at least 10% overall constancy. Diagnostic species (phi ≥ 0.25) are highlighted in grey, highly diagnostic species (phi ≥ 0.5) in dark grey. The complete constancy table combined with the table of the underlying 958 vegetation plots is given in Suppl. material 2.

Class All LYG FES MOL NAR SES
# plots 958 54 339 220 223 114
# plots with bryophyte/lichen treatment 119 19 64 8 11 17
Class LYG (47 taxa)
Linum strictum 3.9 52 2 1 . .
Brachypodium retusum 8.4 52 14 1 . .
Catapodium rigidum 4.3 43 5 1 . .
Lygeum spartum 2.0 33 <1 . . .
Asterolinon linum-stellatum 2.2 33 1 <1 . .
Artemisia herba-alba 1.8 31 . . . .
Thymus vulgaris subsp. vulgaris 9.9 50 20 . . .
Polygala monspeliaca 2.4 33 1 . . .
Trachynia distachya 3.0 35 2 <1 . 1
Teucrium capitatum subsp. capitatum 4.3 35 6 . . .
Bombycilaena erecta 2.8 31 3 . . .
Euphorbia exigua 3.9 33 5 <1 . .
Plantago lagopus subsp. lagopus 1.5 26 . . . .
Plantago albicans 1.5 26 . . . .
Atractylis humilis 1.8 24 1 . . .
[…]
Class FES (21 taxa)
Bromopsis erecta subsp. erecta 27.1 2 65 6 5 11
Carthamus mitissimus 19.4 7 51 1 3 2
Carex humilis 14.5 4 40 . . 1
Potentilla tabernaemontani 19.5 6 48 1 4 10
Coronilla minima 14.2 7 38 <1 . 1
Festuca rectifolia 17.7 4 42 . 2 15
Seseli montanum subsp. montanum 14.1 2 33 1 6 4
Helictochloa pratensis subsp. iberica 20.9 2 46 <1 4 30
Geum sylvaticum 6.8 . 18 . 1 1
Scabiosa columbaria subsp. columbaria 11.1 . 25 4 3 5
Medicago lupulina 20.1 6 39 18 3 8
Onobrychis conferta subsp. hispanica 6.3 2 17 1 . .
Sanguisorba minor aggr. 16.0 17 34 6 6 1
Teucrium chamaedrys 6.8 4 18 . . 2
Trifolium montanum subsp. montanum 6.2 . 15 2 1 .
[…]
Class MOL (33 taxa)
Holcus lanatus 11.6 . 3 44 1 .
Ranunculus acris subsp. friesianus 7.8 . 1 32 <1 .
Agrostis stolonifera subsp. stolonifera 9.1 2 3 34 <1 .
Trifolium fragiferum 6.6 . . 28 1 .
Ranunculus repens 6.5 . . 26 2 .
Poa trivialis subsp. trivialis 8.9 . 6 30 . .
Lolium perenne 11.1 2 4 35 7 .
Schedonorus arundinaceus subsp. arundinaceus 6.4 . 2 25 . .
Juncus articulatus 4.9 . . 21 <1 .
Juncus inflexus 4.3 . . 19 . .
Centaurea debeauxii 6.8 . 4 23 1 .
Anthoxanthum odoratum 10.5 . 4 30 9 2
Rumex acetosa subsp. acetosa 4.8 . <1 19 . 3
Potentilla reptans 6.7 6 2 24 1 .
Veronica chamaedrys subsp. chamaedrys 5.0 . <1 18 3 .
[…]
Class NAR (17 taxa)
Potentilla erecta 16.7 . 1 5 63 4
Galium saxatile 11.5 . <1 <1 48 1
Agrostis capillaris 35.4 . 18 27 86 23
Festuca microphylla 40.2 . 22 19 94 48
Polygala serpyllifolia 8.6 . 2 <1 33 .
Nardus stricta 8.5 . . . 34 5
Danthonia decumbens 17.1 . 10 9 47 4
Agrostis curtisii 5.7 . . . 25 .
Jasione laevis subsp. laevis 5.8 . . . 25 1
Carex pilulifera subsp. pilulifera 5.5 . . <1 23 .
Calluna vulgaris 7.4 . . . 27 8
Veronica officinalis 5.0 . . <1 21 1
Helictochloa marginata subsp. marginata 6.7 . 3 . 24 2
Trifolium alpinum 3.7 . . . 16 .
Vaccinium myrtillus 2.7 . . . 11 1
[…]
Class SES (46 taxa)
Helictotrichon sedenense subsp. sedenense 5.6 . . . <1 46
Carex sempervirens subsp. sempervirens 5.4 . 1 . <1 43
Alchemilla plicatula aggr. 13.5 . 4 . 19 61
Festuca gautieri subsp. scoparia 4.7 . <1 . <1 38
Poa alpina 10.4 . 5 . 12 50
Androsace villosa subsp. villosa 4.4 . 1 . . 32
Paronychia kapela subsp. serpyllifolia 4.6 . 1 . 2 32
Agrostis schleicheri 3.9 . 1 . . 29
Carex ornithopoda 4.8 . 2 . 2 32
Ranunculus carinthiacus 4.1 . 1 . 2 29
Sesleria caerulea subsp. caerulea 4.3 . 2 . <1 29
Trifolium thalii 7.9 . <1 . 13 38
Silene acaulis 3.4 . . . 1 26
Aster alpinus 3.5 . 1 . <1 25
Saxifraga paniculata 2.9 . <1 . . 24
[…]
Anthyllis vulneraria 13.6 4 22 1 1 43
Diagnostic for multiple classes (13 taxa)
Eryngium campestre 16.1 37 32 9 1 .
Genista scorpius 7.0 30 15 . . .
Koeleria vallesiana 25.1 37 53 . . 34
Dactylis glomerata 21.0 52 20 43 3 2
Carex flacca subsp. flacca 25.3 . 45 35 4 3
Pilosella officinarum 29.6 13 41 5 48 13
Thymus praecox 42.5 . 63 1 43 82
Carex caryophyllea 27.9 4 31 4 51 30
Helianthemum canum subsp. canum 14.6 2 27 . 1 39
Teucrium pyrenaicum 11.0 . 24 <1 <1 18
Trifolium repens 30.0 . 17 47 52 8
Campanula scheuchzeri 7.0 . 1 <1 15 25
Plantago alpina 6.5 . 1 . 20 13
Companion species
Lotus corniculatus 44.3 4 53 32 54 43
Plantago lanceolata 37.5 7 50 47 29 11
Trifolium pratense 32.0 4 29 46 37 20
Bellis perennis 31.1 7 26 43 41 15
Achillea millefolium 25.6 2 24 24 41 12
Hypochaeris radicata 24.8 15 19 30 40 9
Plantago media 24.7 . 31 24 30 9
Galium pumilum 23.7 2 40 8 15 34
Briza media subsp. media 22.2 . 38 25 9 9
Brachypodium rupestre 21.5 . 32 19 18 10
Ranunculus bulbosus subsp. bulbosus 21.5 2 28 20 24 11
Cerastium fontanum subsp. vulgare 17.7 . 11 22 35 6
Daucus carota 16.1 19 22 32 . .
Linum catharticum subsp. catharticum 15.7 . 28 3 13 18
Galium verum subsp. verum 14.3 13 20 12 15 2
Potentilla montana 13.6 . 17 1 26 10
Cynosurus cristatus 13.0 . 13 27 10 .
Prunella vulgaris 11.5 . 7 26 12 3
Helianthemum nummularium 11.3 . 21 <1 8 15
Blackstonia perfoliata 11.0 17 25 5 . .
Hippocrepis comosa 10.9 2 20 <1 5 18
Leontodon saxatilis subsp. saxatilis 10.9 19 12 15 9 .
Colchicum montanum 10.8 . 20 1 11 5
Trifolium campestre 10.8 13 19 12 3 .
Phleum pratense 10.5 11 17 15 1 .
Erica vagans 10.4 . 17 . 17 4
[…]
Bryophytes and lichens (based on plots from the Field Workshop)
Class LYG (12 taxa)
Seirophora lacunosa 5.9 37 . . . .
Gyalolechia fulgens 5.9 37 . . . .
Didymodon acutus 23.5 58 25 . . 6
Squamarina cartilaginea 6.7 37 . . . 6
Weissia condensa 7.6 32 3 . . 6
Fulgensia poeltii 4.2 21 2 . . .
Lathagrium cristatum 4.2 21 2 . . .
Enchylium tenax 10.1 32 8 . . 6
[…]
Class FES (5 taxa)
Cladonia rangiformis 14.3 . 27 . . .
Cladonia convoluta 8.4 . 16 . . .
Eurhynchiastrum pulchellum 5.9 . 11 . . .
Campyliadelphus chrysophyllus 12.6 . 20 . . 12
Cladonia foliacea 4.2 . 8 . . .
Class MOL (2 taxa)
Brachythecium laetum 4.2 . . 50 9 .
Rhytidiadelphus squarrosus 2.5 . 3 13 . .
Class NAR (3 taxa)
Tortula acaulon 1.7 . . . 18 .
Lophocolea minor 0.8 . . . 9 .
Tortula inermis 0.8 . . . 9 .
Class SES (20 taxa)
Cladonia pocillum 5.9 . 3 . . 29
Tortella tortuosa 20.2 . 23 . 9 47
Fissidens dubius 15.1 . 19 . . 35
Mnium marginatum 2.5 . . . . 18
Polytrichum juniperinum 2.5 . . . . 18
Scapania calcicola 2.5 . . . . 18
Tortella inclinata 10.9 5 8 . 9 35
Ptychostomum capillare aggr. 11.8 5 13 . . 29
[…]
Ditrichum pusillum 10.1 11 6 . 9 29
Diagnostic for multiple classes
Tortella squarrosa 31.1 32 41 . . 29
Abietinella abietina 10.9 . 19 13 . .
Ctenidium molluscum 31.1 . 44 13 . 47
Flexitrichum gracile 21.0 . 33 . . 24
Companion species
Homalothecium lutescens 34.5 16 42 50 9 35
Weissia controversa 23.5 42 23 13 9 18
Hypnum cupressiforme 22.7 5 28 . 36 24
Pseudoscleropodium purum 13.4 . 20 13 9 6
Calliergonella cuspidata 12.6 . 20 13 9 .
Figure 3. 

Study area (Navarre) and location of grassland relevés classified to classes according to expert system analysis.

FES – Festuco-Brometea

After applying the expert system most relevés of Festuca-Brometea, Festuco-Ononidetea and Ononido-Rosmarinetea were classified in the FES group (Table 1). The diagnostic species for this group with highest fidelity index were Bromopsis erecta subsp. erecta, Carthamus mitissimus, Carex humilis, Potentilla tabernaemontani, Coronilla minima, Festuca rectifolia and Seseli montanum subsp. montanum (Table 2).

This group (FES) occupies the transition areas between the Pyrenees and Cantabrian mountains and the Mediterranean region (Figure 3). These communities grow at moderate elevations, mostly in the upper colline and montane belts, and with average precipitation and temperatures of 1,230 mm and 10 °C, respectively (Table 3).

Table 3.

Comparison of climatic, structural, ecological and diversity characteristics among the five classes. The p-values and significance levels refer to ANOVAs.

Parameter LYG FES MOL NAR SES p-value Sig.
Total number of relevés 54 339 220 223 114
Number of relevés from EDGG FW 19 64 8 11 17
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
Parameters calculated for all relevés
Geographical and climatic parameters
Elevation [m a.s.l.] 439 ± 157 853 ± 286 577 ± 272 1265 ± 378 1752 ± 386 <0.001 ***
Mediterranity index 1.36 ± 0.46 0.66 ± 0.19 0.77 ± 0.31 0.41 ± 0.1 0.36 ± 0.08 <0.001 ***
Annual mean temperature [°C] 13.2 ± 1.3 10.5 ± 1.5 11.8 ± 1.6 8.0 ± 2.4 5.3 ± 2.7 <0.001 ***
Mean annual precepitation [mm] 686 ± 260 1232 ± 283 1134 ± 331 1751 ± 271 1865 ± 232 <0.001 ***
Parameters calculated for relevés from EDGG Field Workshop
Vegetation structure
Cover vegetation total [%] 67 ± 22 81 ± 19 98 ± 2 86 ± 9 55 ± 22 <0.001 ***
Cover shrub layer [%] 1 ± 1 1 ± 3 0 ± 0 0 ± 0 0 ± 0 0.138
Cover herb layer [%] 55 ± 25 76 ± 20 98 ± 2 77 ± 25 51 ± 22 <0.001 ***
Cover cryptogam layer [%] 19 ± 21 16 ± 18 31 ± 32 1 ± 2 10 ± 10 0.005 **
Cover litter [%] 16 ± 17 9 ± 14 8 ± 12 6 ± 6 14 ± 25 0.365 n.s.
Herb layer maximum height [cm] 66 ± 26 65 ± 31 108 ± 32 31 ± 17 24 ± 19 <0.001 ***
Species richness
Species richness (total) 35.6 ± 6.8 55.3 ± 14.5 45.3 ± 14.7 40.5 ± 6.9 44.0 ± 11.7 <0.001 ***
Species richness (vascular plants) 29.2 ± 7.5 48.0 ± 11.9 43.5 ± 14.0 37.5 ± 6.4 34.4 ± 7.7 <0.001 ***
Species richness (cryptogams) 6.4 ± 4.2 7.3 ± 4.9 2.0 ± 1.7 2.9 ± 2.0 9.6 ± 6.2 <0.001 ***
Species richness (bryophytes) 3.2 ± 2.0 6.3 ± 4.2 2.0 ± 1.7 2.5 ± 1.6 7.2 ± 5.6 <0.001 ***
Species richness (lichens) 3.2 ± 3.2 1.0 ± 1.3 0.0 ± 0.0 0.4 ± 0.7 2.4 ± 2.3 <0.001 ***
Topography
Southing (cosine of aspect) 0.1 ± 0.6 -0.3 ± 0.68 -0.46 ± 0.65 0.24 ± 0.69 0.08 ± 0.89 0.019 *
Inclination [°] 8 ± 9 16 ± 13 6 ± 6 26 ± 9 32 ± 11 <0.001 ***
Maximum microrelief [cm] 7 ± 7 9 ± 8 4 ± 3 9 ± 4 29 ± 26 <0.001 ***
Soil parameters
Soil depth mean [cm] 12 ± 6 16 ± 8 17 ± 5 36 ± 16 6 ± 5 <0.001 ***
Soil depth CV 54 ± 32 50 ± 40 49 ± 34 30 ± 16 97 ± 51 0.001 ***
Cover rocks and stones [%] 6 ± 13 7 ± 14 0 ± 0 2 ± 3 35 ± 23 <0.001 ***
Cover gravel [%] 19 ± 29 6 ± 15 0 ± 0 1 ± 1 13 ± 16 0.011 *
Cover fine soil [%] 75 ± 35 88 ± 22 100 ± 0 97 ± 3 52 ± 32 <0.001 ***
Coarse fragments [%] 16 ± 13 22 ± 17 15 ± 14 12 ± 8 24 ± 16 0.139 n.s.
Fine fragments < 2mm [%] 84 ± 13 78 ± 17 85 ± 14 88 ± 8 76 ± 16 0.139 n.s.
pH 7.69 ± 0.24 7.52 ± 0.42 7.66 ± 0.99 6.8 ± 0.29 7.46 ± 0.38 <0.001 ***
Electrical conductivity [µS/cm] 283 ± 184 232 ± 86 168 ± 78 146 ± 80 310 ± 158 0.002 **
CaCO3 [%] 40.7 ± 10.5 26.7 ± 19.1 8.5 ± 8.5 4 ± 1.1 4.6 ± 1.8 <0.001 ***
Organic matter [%] 0.6 ± 0.6 1.4 ± 0.8 1.2 ± 0.3 1.3 ± 0.2 2.2 ± 0.7 <0.001 ***

MOL – Molinio-Arrhenatheretea (Figure 2C)

86% of the relevés previously assigned to the Molinio-Arrhenetheretea were included in the group MOL, together with 16% of the relevés of Festuco-Brometea. This group is characterized by several diagnostic species of the class Molinio-Arrhenatheretea, such as Agrostis stolonifera subsp. stolonifera, Anthoxanthum odoratum, Holcus lanatus, Juncus articulatus, J. inflexus, Lolium perenne, Poa trivialis subsp. trivialis, Ranunculus acris subsp. friesianus, R. repens and Trifolium fragiferum subsp. fragiferum, among other species (Table 2).

The relevés from Festuco-Brometea class classified in the group MOL had been originally assigned to the associations Seseli-Brachypodietum and Elytrigio-Brachypodietum phoenicoidis from Festuco-Brometea. The presence of Agrimonia eupatoria, Agrostis stolonifera subsp. stolonifera, Bromus hordeaceus subsp. hordeaceus, Poa trivialis subsp. trivialis, Potentilla reptans, Ranunculus acris subsp. friesianus and Schedonorus arundinaceus subsp. arundinaceus relates these relevés to this group (MOL).

This group is widely distributed throughout the study area (Figure 3), although it does not reach high elevations. In the temperate zone it can be found in the meso- and supratemperate, and in the Mediterranean zone it is restricted to wet soils, both in the meso- and the supramediterranean. These grasslands and pastures grow on flat areas with a proportion of 100% fine soil, which results in an almost total vegetation cover (Table 3).

NAR – Nardetea strictae (Figure 2B)

Table 1 shows that almost all the relevés originally classified in the class Nardetea strictae have been classified in group NAR by the expert system. Most relevés of the class Sedo-Scleranthetea were also classified in this group, as well as some relevés of Festuco-Brometea (19%) and Molinio-Arrhenateretea (8%). The diagnostic species include acidophilous taxa such as Agrostis capillaris, Carex pilulifera subsp. pilulifera, Danthonia decumbens, Galium saxatile, Jasione laevis subsp. laevis or Potentilla erecta (Table 2).

Relevés from Festuco-Brometea included in this group correspond to communities of the association Calamintho-Seselietum montani that grow in places with a very humid ombroclimate, which causes acidification of the soil leading to the presence of acidophilous species diagnostic of Nardetea. As regards Molinio-Arrhenatheretea, relevés originally assigned to the association Merendero-Cynosuretum were classified in this group. In both cases, the species shared with Nardetea were Agrostis capillaris, Carex pilulifera subsp. pilulifera, Danthonia decumbens, Festuca microphylla, Galium saxatile, Helictochloa marginata subsp. marginata, Luzula campestris, Jasione laevis subsp. laevis, Polygala serpyllifolia, Potentilla erecta, among others.

The relevés of this group are widely distributed in the montane and subalpine belts of the Pyrenees and Basque-Cantabrian mountains under temperate climate (Figure 3).

SES – Elyno-Seslerietea (Figure 2A)

The expert system classification within the group SES included most of the relevés of the class Elyno-Seslerietea and 23% of relevés from Festuco-Ononidetea. Agrostis schleicheri, Alchemilla plicatula aggr., Androsace villosa subsp. villosa, Carex ornithopoda subsp. ornithopoda, C. sempervirens subsp. sempervirens, Festuca gautieri subsp. scoparia, Helictotrichon sedenense subsp. sedenense, Paronychia kapela subsp. serpyllifolia, Poa alpina, Ranunculus carinthiacus, Sesleria caerulea subsp. caerulea, Silene acaulis and Trifolium thalii are diagnostic species of this group (Table 2).

Relevés of Festuco-Ononidetea included in this group correspond to communities of the Pyrenean subalpine alliance Festucion scopariae, which share most of the diagnostic species of the group, such as Aster alpinus, Minuartia verna subsp. verna, and Saxifraga paniculata, in addition to those aforementioned.

This group SES includes the plots at highest elevations in calcareous mountains, in the upper montane and subalpine belts. In these cases, they share territories with the previous group NAR, but in rocky calcareous places (Figure 3). However, the concentration of calcium carbonate in the soil is very low due to the decarbonation effect caused by high precipitation and snow accumulation (Table 3).

Ordination

The NMDS ordination diagram clearly differentiated between the five groups defined by our class expert system (Figure 4). Axis 1 distributes Lygeo-Stipetea, Festuco-Brometea, Molinio-Arrhenatheretea, Nardetea strictae and Elyno-Seslerietea along a decreasing mediterraneity and increasing precipitation gradient. Axis 2 separates classes Molinio-Arrhenatheretea and Nardetea, in the upper part, from the others. This axis could be related to soil moisture.

Figure 4. 

NMDS ordination of all grassland relevés. Eigenvalues: Axis 1 – 0.4434, Axis 2 – 0.4010, Axis 3 (not shown) – 0.1556. Med stands for Mediterraneity Index.

Site conditions and biodiversity of different classes

The differences between classes regarding elevation and climatic conditions can be seen in Table 3 and Figure 5. The class Lygeo-Stipetea (LYG) shows the highest Mediterraneity index and the highest mean annual temperature and is generally present at lower elevations with the lowest annual precipitation. On the other hand, the classes Nardetea (NAR) and Elyno-Seslerietea (SES) develop at the highest elevations, linked to the highest annual precipitation and lowest mean annual temperature and Mediterraneity Index.

Figure 5. 

Comparison of nine ecological variables among the five classes. For elevation and Mediterraneity Index, all relevés were analysed, whereas for the rest of variables only relevés from EDGG Field Workshop were used. Letters represent homogeneous groups (at α = 0.05) according to Tukey’s post-hoc test following a significant ANOVA.

Regarding soil, topographic and structural variables (Table 3, Figure 5), the class Nardetea represents the highest soil depth and is also the most acidophilous community. The class Elyno-Seslerietea is characterised by a higher cover of stones and rocks as well as higher soil organic matter content, and, together with Nardetea and Molinio-Arrhenatheretea, is the poorest in soil carbonate content. Conversely, Lygeo-Stipetea is signified by its high soil carbonate content and low soil organic matter. Molinio-Arrhenatheretea is distinghuished by its high cover of the herb layer and cryptogams.

The total species richness is highest in Festuco-Brometea, although differences with the second richer class Molinio-Arrhenatheretea are not significant (Figure 6). Festuco-Brometea is also rich in vascular plants and bryophytes, although for the former values do not significantly differ from those of Molinio-Arrhenatheretea, and for the latter from those of Elyno-Seslerietea. The latter class stands out because of its high cryptogam richness, both in bryophytes and lichens. On the other hand, Molinio-Arrhenetheretea and Nardetea are the poorest in cryptogams. Finally, Lygeo-Stipetea shares with Elyno-Seslerietea the high number of lichens, although its richness in bryophytes is lower.

Figure 6. 

Comparison of species richness divided into four groups (total species, vascular plants, bryophytes and lichens) among the five classes using the relevés from EDGG Field Workshop. Letters represent homogeneous groups (at α = 0.05) according to Tukey’s post-hoc test following a significant ANOVA.

Subdivision of the Festuco-Brometea into orders, alliances and associations

The TWISPAN analysis for the group FES related to the class Festuco-Brometea resulted in four main divisions that can be interpreted at order and alliance levels (Figure 7). Order 1 grouped relevés originally classified in the classes Ononido-Rosmarinetea (Thymelaeo-Aphyllanthetum monspeliensis) and Festuco-Ononidetea (Ononidetalia striatae: Helianthemo-Koelerietum vallesianae; Festuco-Poetalia ligulatae: Jurineo-Festucetum hystricis). The dry grasslands of the Thymelaeo-Aphyllanthetum association were included in alliance 1.1. The two associations from Festuco-Ononidetea, Helianthemo-Koelerietum and Jurineo-Festucetum, were merged in the alliance 1.2.

Figure 7. 

Dendogram of the modified TWINSPAN classification of the 339 relevés from Festuco-Brometea into two orders and four alliances.

Diagnostic species for order 1 were Carex humilis, Galium lucidum subsp. fruticescens, Helianthemum apenninum subsp. apenninum and Koeleria vallesiana (Table 4). The alliance 1.1 was characterized by the presence of Mediterranean species such as Aphyllanthes monspeliensis, Brachypodium retusum, Coris monspeliensis, Helictochloa bromoides and Thymus vulgaris subsp. vulgaris (Table 4). Only one association was recognised in this alliance and corresponded to Thymelaeo-Aphyllanthetum monspeliensis, as both the type relevé of the association (Braun-Blanquet 1966) and the type of the subassociation brachypodietum retusi (Berastegi et al. 2005) were placed in this group by the expert system. Inside the alliance 1.2 the relevés were split into two groups. The types of the associations Jurineo-Festucetum hystricis and Helianthemo-Koelerietum vallesianae, both described by Berastegi (2013), were classified to the groups 1.2.1 and 1.2.2. respectively. The diagnostic species for this alliance were Asperula pyrenaica, Ononis striata, Plantago atrata subsp. discolor and Sedum album, among others.

Table 4.

Abridged constancy table of the class Festuco-Brometea and its subordinate syntaxa. Values are percentage constancies, and species are ordered by decreasing phi-values in the respective syntaxon, respectively by decreasing overall constancy for non-diagnostic species. In the upper part vascular plants are given, in the lower part bryophytes and lichens, whose constancies and fidelities have been calculated based on the plots of the EDGG Field Workshop only where they have been recorded (in italics if based on data from a single plot, with ? if no such data were available for any plot). In the table, the 15 vascular plant taxa and the eight non-vascular plant taxa with the highest fidelity in a syntaxon are shown, plus all taxa that are diagnostic for multiple syntaxa and all taxa with at least 10% overall constancy. Diagnostic species (phi ≥ 0.25) for higher syntaxa highlighted in light grey, diagnostic species for associations in dark grey, while differential species of associations within the respective alliance are given with a frame. The complete constancy table combined with the table of the underlying 339 vegetation plots is given in Suppl. material 14.

Class Class Ord. Ord. All. All. All. All. Assoc. Assoc. Assoc. Assoc. Assoc. Assoc. Assoc. Assoc.
Order 1 2 1 1 2 2 1 1 1 2 2 2 2 2
Alliance 1.1 1.2 2.1 2.2 1.1 1.2 1.2 2.1 2.1 2.2 2.2 2.2
Association 1.1.1 1.2.1 1.2.2 2.1.1 2.1.2 2.2.1 2.2.2 2.2.3
# plots 339 139 200 52 87 40 160 52 25 61 14 26 12 78 69
Field Workshop (with bryophytes + lichens) 64 23 41 18 5 8 33 18 <1 5 1 7 1 20 12
Ord. 1 (4 taxa)
Koeleria vallesiana 53.1 92 26 85 97 15 29 85 100 95 36 4 <1 27 36
Carex humilis 40.1 66 22 65 67 8 26 65 96 56 14 4 42 28 19
Helianthemum apenninum subsp. apenninum 13.6 29 3 19 34 3 3 19 32 36 <1 4 <1 3 4
Galium lucidum subsp. fruticescens 9.7 21 2 15 24 3 2 15 24 25 <1 4 17 <1 1
All. 1.1 (38 taxa + 1 multiple diagnostic taxon)
Brachypodium retusum 14.5 29 5 75 1 18 1 75 <1 2 43 4 8 1 <1
Thymus vulgaris subsp. vulgaris 20.1 45 3 81 24 8 1 81 44 16 7 8 <1 1 1
Lavandula latifolia 7.1 17 1 42 1 3 <1 42 4 <1 <1 4 <1 <1 <1
Aphyllanthes monspeliensis 14.7 24 9 58 3 10 8 58 4 3 14 8 <1 13 4
Coris monspeliensis 6.8 14 2 38 <1 8 <1 38 <1 <1 14 4 <1 <1 <1
Teucrium chamaedrys 18.0 35 7 60 20 10 6 60 16 21 14 8 42 3 3
Helictochloa bromoides 6.2 13 2 35 <1 8 <1 35 <1 <1 14 4 <1 <1 <1
Bupleurum rigidum subsp. rigidum 4.7 11 1 29 <1 3 <1 29 <1 <1 7 <1 <1 <1 <1
Linum appressum 9.7 17 5 40 2 8 4 40 4 2 21 <1 8 4 4
Genista scorpius 15.0 23 10 58 2 35 3 58 4 2 50 27 8 4 1
Dorycnium pentaphyllum subsp. pentaphyllum 16.5 24 12 58 3 33 6 58 4 3 64 15 33 5 3
Santolina villosa 3.8 9 1 23 <1 <1 1 23 <1 <1 <1 <1 8 <1 <1
Coronilla minima 38.3 60 23 79 49 25 23 79 72 41 36 19 8 29 17
Fumana ericifolia 3.5 8 1 21 <1 <1 1 21 <1 <1 <1 <1 <1 <1 1
Linum narbonense 6.2 12 3 29 1 5 2 29 <1 2 14 <1 8 3 <1
[…]
Asperula cynanchica 17.7 22 15 44 9 8 16 44 4 11 14 4 17 18 14
Catananche caerulea 13.6 17 12 42 1 23 9 42 <1 2 21 23 <1 17 1
Festuca marginata subsp. andres-molinae 10.3 14 8 35 2 20 4 35 8 <1 29 15 <1 9 <1
Assoc. 1.1.1 (7 taxa)
Rhamnus alaternus subsp. alaternus 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Odontites kaliformis 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Lithodora fruticosa 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Gladiolus illyricus 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Atractylis humilis 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Aster willkommii 1.2 3 <1 8 <1 <1 <1 8 <1 <1 <1 <1 <1 <1 <1
Helichrysum stoechas subsp. stoechas 1.8 4 <1 10 1 <1 <1 10 <1 2 <1 <1 <1 <1 <1
All. 1.2 (8 taxa + 1 multiple diagnostic)
Sedum album 14.2 27 6 2 41 <1 7 2 48 39 <1 <1 8 <1 14
Ononis striata 4.7 12 <1 2 17 <1 <1 2 20 16 <1 <1 <1 <1 <1
Asperula pyrenaica 12.7 19 8 4 29 3 9 4 28 30 <1 4 <1 4 17
Plantago atrata subsp. discolor 5.6 12 2 2 17 <1 2 2 12 20 <1 <1 <1 3 1
Anthyllis vulneraria 22.1 29 18 8 41 15 18 8 40 43 14 15 <1 15 23
Thymus praecox 62.8 60 65 33 76 23 76 33 80 74 21 23 42 67 91
Oreochloa confusa 3.8 7 2 <1 11 <1 2 <1 16 8 <1 <1 <1 <1 4
Dianthus pungens subsp. brachyanthus 3.2 6 1 <1 10 <1 1 <1 16 8 <1 <1 <1 <1 3
Brimeura amethystina 3.2 6 1 <1 10 <1 1 <1 4 13 <1 <1 <1 1 1
Assoc. 1.2.1 (13 taxa)
Arenaria grandiflora subsp. grandiflora 13.0 29 2 4 44 <1 3 4 88 25 <1 <1 <1 <1 6
Festuca hystrix 5.9 14 <1 4 21 <1 <1 4 56 7 <1 <1 <1 <1 <1
Helianthemum canum subsp. canum 26.8 49 12 12 71 <1 14 12 100 59 <1 <1 <1 12 20
Klasea nudicaulis 6.5 15 1 4 22 <1 1 4 48 11 <1 <1 <1 <1 1
Anthyllis montana 2.9 7 <1 <1 11 <1 <1 <1 32 3 <1 <1 <1 <1 <1
Jurinea humilis 3.5 8 1 <1 13 <1 1 <1 28 7 <1 <1 <1 <1 1
Erucastrum nasturtiifolium subsp. sudrei 1.8 4 <1 <1 7 <1 <1 <1 20 2 <1 <1 <1 <1 <1
Trinia glauca 7.7 17 1 10 22 <1 1 10 36 16 <1 <1 <1 3 <1
Festuca ovina aggr. 11.2 18 7 8 24 <1 8 8 44 16 <1 <1 8 8 9
Aster alpinus 1.2 3 <1 <1 5 <1 <1 <1 16 <1 <1 <1 <1 <1 <1
Paronychia kapela subsp. kapela 0.9 2 <1 <1 3 <1 <1 <1 12 <1 <1 <1 <1 <1 <1
Arenaria erinacea 0.9 2 <1 <1 3 <1 <1 <1 12 <1 <1 <1 <1 <1 <1
Scilla verna 6.8 10 5 4 14 3 5 4 28 8 <1 4 <1 5 4
Assoc. 1.2.2 (5 taxa + 1 multiple diagnostic taxon + 1 differential taxon)
Conopodium arvense 4.4 9 2 <1 14 <1 2 <1 <1 20 <1 <1 <1 3 1
Sedum acre 2.9 6 1 <1 10 <1 1 <1 <1 15 <1 <1 <1 <1 1
Deschampsia media subsp. hispanica 3.2 7 1 <1 11 3 <1 <1 <1 16 <1 4 <1 <1 <1
Helianthemum salicifolium 1.5 4 <1 <1 6 <1 <1 <1 <1 8 <1 <1 <1 <1 <1
Erodium glandulosum 1.5 4 <1 <1 6 <1 <1 <1 <1 8 <1 <1 <1 <1 <1
Medicago lupulina 38.9 33 43 12 46 33 46 12 4 64 21 38 8 54 43
Ord. 2 (12 taxa)
Lotus corniculatus 52.8 24 73 13 30 58 77 13 20 34 57 58 17 85 78
Trifolium pratense 28.6 4 46 2 6 45 46 2 <1 8 29 54 8 62 35
Briza media subsp. media 38.3 17 54 25 11 45 56 25 4 15 43 46 33 83 29
Trifolium ochroleucon 15.6 1 26 <1 2 20 27 <1 <1 3 7 27 <1 47 9
Trifolium repens 16.5 2 27 2 2 20 28 2 <1 3 <1 31 <1 27 35
Cynosurus cristatus 12.7 <1 22 <1 <1 28 20 <1 <1 <1 7 38 <1 35 7
Ranunculus bulbosus subsp. bulbosus 28.0 12 40 17 8 45 38 17 4 10 21 58 8 44 38
Plantago lanceolata 50.4 32 64 23 37 50 67 23 12 48 43 54 <1 73 72
Endressia castellana 9.4 <1 16 <1 <1 10 18 <1 <1 <1 <1 15 25 23 10
Ononis spinosa 13.0 2 21 2 2 28 19 2 <1 3 7 38 <1 35 4
Trisetum flavescens subsp. flavescens 11.8 2 19 4 1 20 18 4 <1 2 <1 31 <1 31 7
Festuca nigrescens 9.1 1 15 <1 1 13 16 <1 <1 2 <1 19 17 24 4
All. 2.1 (11 taxa + 1 multiple diagnostic taxon)
Schedonorus arundinaceus subsp. fenas 5.9 <1 10 <1 <1 38 3 <1 <1 <1 36 38 <1 5 1
Centaurea jacea 17.1 6 25 13 2 55 17 13 <1 3 57 54 17 29 3
Arrhenatherum elatius 6.2 1 10 4 <1 33 4 4 <1 <1 29 35 33 3 <1
Convolvulus arvensis 4.4 1 7 2 <1 28 2 2 <1 <1 21 31 <1 3 1
Brachypodium phoenicoides 10.0 8 12 19 1 43 4 19 <1 2 43 42 <1 4 4
Blackstonia perfoliata 24.8 23 26 58 2 68 16 58 <1 3 79 62 <1 27 6
Daucus carota 21.8 10 30 17 6 53 24 17 <1 8 36 62 17 44 4
Carex flacca subsp. flacca 45.1 26 59 58 7 80 53 58 4 8 86 77 58 81 22
Agrimonia eupatoria 4.1 1 7 2 <1 20 3 2 <1 <1 14 23 <1 6 <1
Poa compressa 3.2 1 5 <1 1 18 2 <1 <1 2 7 23 <1 4 <1
Dactylis glomerata 19.8 15 23 27 8 48 17 27 4 10 29 58 58 21 6
Medicago sativa subsp. sativa 1.2 <1 2 <1 <1 10 <1 <1 <1 <1 7 12 <1 <1 <1
Assoc. 2.1.1 (7 taxa + 2 differential taxa)
Plantago maritima subsp. serpentina 6.8 6 7 15 1 25 3 15 <1 2 57 8 <1 3 3
Festuca capillifolia 5.3 4 7 6 2 28 1 6 4 2 50 15 <1 3 <1
Jasonia tuberosa 6.2 9 4 21 2 15 1 21 <1 3 43 <1 <1 1 1
Prunella hyssopifolia 11.5 8 14 19 1 35 9 19 <1 2 57 23 <1 15 3
Agrostis stolonifera subsp. stolonifera 2.7 <1 5 <1 <1 18 1 <1 <1 <1 29 12 <1 3 <1
Lotus tenuis 0.6 <1 1 <1 <1 5 <1 <1 <1 <1 14 <1 <1 <1 <1
Lathyrus latifolius 0.6 <1 1 <1 <1 5 <1 <1 <1 <1 14 <1 <1 <1 <1
Assoc. 2.1.2 (28 taxa + 3 differential taxa)
Phleum pratense 17.1 4 26 10 1 53 19 10 <1 2 14 73 <1 28 13
Poa trivialis subsp. trivialis 5.6 <1 10 <1 <1 28 5 <1 <1 <1 <1 42 <1 8 3
Vicia parviflora 3.2 <1 6 <1 <1 23 1 <1 <1 <1 <1 35 <1 1 1
Brachypodium phoenicoides x rupestre 9.4 2 15 6 <1 40 8 6 <1 <1 7 58 8 12 4
Xeranthemum cylindraceum 2.7 1 4 2 <1 18 1 2 <1 <1 <1 27 <1 <1 1
Trifolium campestre 18.6 7 27 6 8 40 23 6 8 8 <1 62 <1 24 26
Vicia sativa subsp. nigra 5.9 2 9 2 2 25 4 2 <1 3 <1 38 8 6 1
Iris spuria subsp. maritima 1.8 <1 3 <1 <1 13 1 <1 <1 <1 <1 19 <1 1 <1
Gaudinia fragilis 2.1 <1 4 <1 <1 13 1 <1 <1 <1 <1 19 <1 3 <1
Trifolium angustifolium 2.4 1 4 2 <1 13 1 2 <1 <1 <1 19 <1 <1 3
Lathyrus pratensis subsp. pratensis 1.5 <1 3 <1 <1 10 1 <1 <1 <1 <1 15 <1 1 <1
Jacobaea vulgaris 3.2 <1 6 <1 <1 18 3 <1 <1 <1 7 23 <1 5 <1
Allium oleraceum 1.8 <1 3 <1 <1 10 1 <1 <1 <1 <1 15 <1 1 1
Cerastium fontanum subsp. vulgare 10.6 4 15 <1 7 23 13 <1 4 7 <1 35 <1 14 14
Picris hieracioides 7.1 4 9 12 <1 23 6 12 <1 <1 7 31 <1 10 1
[…]
Eryngium campestre 32.4 29 35 58 13 58 29 58 8 15 29 73 25 31 28
Galium verum subsp. verum 19.8 9 27 6 11 38 24 6 <1 16 14 50 17 22 29
Anacamptis pyramidalis 10.6 7 13 19 <1 28 9 19 <1 <1 14 35 <1 19 <1
All. 2.2 (10 taxa + 1 multiple diagnostic taxon)
Brachypodium rupestre 32.4 12 47 12 11 3 58 12 4 15 7 <1 92 73 36
Festuca microphylla 22.4 4 35 2 6 3 43 2 <1 8 7 <1 25 46 43
Achillea millefolium 24.5 7 37 6 8 13 43 6 12 7 7 15 8 47 42
Agrostis capillaris 17.7 3 28 <1 5 5 34 <1 4 5 <1 8 8 37 35
Erica vagans 17.1 3 27 6 1 13 31 6 4 <1 <1 19 58 41 14
Potentilla montana 16.8 3 27 <1 5 8 31 <1 4 5 <1 12 25 24 39
Helianthemum nummularium 21.2 7 31 <1 11 <1 39 <1 <1 16 <1 <1 17 36 46
Danthonia decumbens 10.3 1 17 <1 1 3 21 <1 <1 2 <1 4 <1 29 14
Scabiosa columbaria subsp. columbaria 25.4 12 35 10 14 10 41 10 <1 20 7 12 42 56 23
Gentiana verna subsp. verna 5.6 1 9 <1 1 <1 11 <1 <1 2 <1 <1 <1 9 16
Assoc. 2.2.1 (21 taxa + 1 multiple diagnostic taxon + 2 differential taxa)
Vincetoxicum hirundinaria subsp. intermedium 3.8 4 4 4 3 <1 5 4 4 3 <1 <1 58 1 <1
Sesleria autumnalis 2.7 1 4 <1 2 <1 4 <1 <1 3 <1 <1 50 1 <1
Tanacetum corymbosum subsp. corymbosum 2.9 1 4 2 1 <1 5 2 <1 2 <1 <1 33 5 <1
Genista hispanica subsp. occidentalis 15.9 7 22 10 6 10 25 10 8 5 7 12 67 32 9
Euphorbia characias 2.1 2 2 4 1 <1 3 4 <1 2 <1 <1 25 <1 1
Euphorbia amygdaloides 0.6 <1 1 <1 <1 <1 1 <1 <1 <1 <1 <1 17 <1 <1
Cruciata laevipes 0.6 <1 1 <1 <1 <1 1 <1 <1 <1 <1 <1 17 <1 <1
Teucrium pyrenaicum 23.9 22 25 10 30 3 31 10 28 30 7 <1 67 29 26
Pimpinella major subsp. major 1.2 <1 2 <1 <1 <1 3 <1 <1 <1 <1 <1 17 1 1
Helictotrichon cantabricum 6.8 6 8 12 2 13 6 12 4 2 21 8 42 5 1
Viola alba aggr. 3.5 4 3 12 <1 <1 4 12 <1 <1 <1 <1 25 4 <1
Dianthus hyssopifolius subsp. hyssopifolius 4.1 3 5 <1 5 <1 6 <1 <1 7 <1 <1 25 3 7
Helleborus foetidus 0.9 <1 2 <1 <1 3 1 <1 <1 <1 <1 4 17 <1 <1
Senecio lagascanus 1.8 3 1 4 2 <1 1 4 <1 3 <1 <1 17 <1 <1
Echium vulgare subsp. vulgare 2.1 1 3 2 1 <1 3 2 <1 2 <1 <1 17 3 1
Assoc. 2.2.2 (4 taxa + 1 multiple diagnostic taxon + 2 differential taxa)
Leontodon hispidus 9.1 1 15 2 1 <1 18 2 <1 2 <1 <1 <1 32 6
Plantago media 31.3 9 47 8 9 25 53 8 8 10 14 31 8 72 39
Linum catharticum subsp. catharticum 27.7 12 39 19 7 25 43 19 <1 10 29 23 <1 63 28
Polygala vulgaris subsp. vulgaris 7.1 1 12 2 <1 5 13 2 <1 <1 <1 8 <1 24 1
Prunella vulgaris 6.8 1 11 2 1 5 12 2 <1 2 <1 8 <1 21 4
Holcus lanatus 2.9 <1 5 <1 <1 3 6 <1 <1 <1 <1 4 <1 12 <1
Assoc. 2.2.3 (10 taxa + 1 multiple diagnostic taxon)
Carex caryophyllea 31.3 14 43 6 20 13 51 6 8 25 7 15 17 36 72
Festuca rectifolia 42.5 45 41 6 68 8 49 6 36 80 <1 12 17 26 81
Bellis perennis 25.7 12 35 6 16 18 39 6 <1 23 7 23 <1 31 57
Colchicum montanum 20.4 17 23 2 25 3 28 2 8 33 <1 4 <1 19 43
Alchemilla plicatula aggr. 3.5 1 6 <1 1 <1 7 <1 <1 2 <1 <1 <1 1 14
Aira caryophyllea subsp. caryophyllea 9.1 5 12 2 7 8 13 2 <1 10 <1 12 <1 4 26
Vicia pyrenaica 2.9 1 4 <1 2 <1 5 <1 <1 2 <1 <1 <1 <1 12
Poa alpina 4.7 3 6 <1 5 <1 8 <1 <1 7 <1 <1 <1 1 16
Cerastium arvense 8.3 9 8 <1 14 <1 10 <1 8 15 <1 <1 <1 <1 23
Erinus alpinus 3.8 3 5 <1 5 <1 6 <1 <1 5 <1 <1 <1 <1 13
Euphrasia salisburgensis 2.1 <1 4 <1 <1 <1 4 <1 <1 <1 <1 <1 <1 1 9
Other species (class character species and companion species)
Bromopsis erecta subsp. erecta 65.2 60 69 69 55 53 73 69 32 66 29 65 75 82 61
Carthamus mitissimus 50.7 56 47 58 55 23 53 58 44 61 14 27 33 63 45
Potentilla tabernaemontani 48.1 56 43 52 59 20 48 52 36 69 21 19 8 36 68
Helictochloa pratensis subsp. iberica 45.7 48 44 52 46 18 51 52 36 51 7 23 42 51 51
Pilosella officinarum 41.3 31 49 40 25 23 55 40 8 33 29 19 <1 59 61
Galium pumilum 39.8 27 49 44 17 48 49 44 4 23 36 54 58 60 33
Sanguisorba minor aggr. 33.9 29 37 44 21 20 41 44 8 26 14 23 25 54 30
Seseli montanum subsp. montanum 32.7 32 34 23 37 35 33 23 32 39 21 42 8 32 38
Hippocrepis comosa 20.4 12 27 13 10 10 31 13 8 11 14 8 8 41 22
Hypochaeris radicata 18.9 10 25 15 7 25 25 15 <1 10 43 15 17 32 19
Geum sylvaticum 18.0 12 23 12 11 10 26 12 8 13 7 12 17 32 20
Onobrychis conferta subsp. hispanica 16.8 20 15 31 14 8 16 31 16 13 14 4 <1 28 6
Trifolium montanum subsp. montanum 15.3 6 22 2 9 15 23 2 8 10 7 19 <1 33 14
Clinopodium alpinum subsp. pyrenaeum 14.2 19 11 13 23 <1 13 13 8 30 <1 <1 <1 10 19
Leucanthemum pallens 13.6 9 17 19 3 23 15 19 <1 5 14 27 17 26 3
Filipendula vulgaris 12.7 6 17 <1 10 13 18 <1 12 10 7 15 33 13 20
Astragalus monspessulanus subsp. monspessulanus 12.4 19 8 15 21 5 9 15 28 18 7 4 <1 10 9
Leontodon saxatilis subsp. saxatilis 12.1 8 15 8 8 25 13 8 <1 11 21 27 8 12 14
Prunella laciniata 12.1 4 18 8 1 8 21 8 <1 2 <1 12 8 26 17
Thymelaea ruizii 11.5 12 12 21 6 10 12 21 4 7 14 8 8 17 7
Ononis pusilla 10.3 19 4 25 16 5 4 25 8 20 14 <1 <1 3 6
Bellis sylvestris 10.0 14 8 23 8 10 7 23 8 8 7 12 <1 10 4
[…]
Bryophytes and lichens (based on plots from the Field Workshop)
Ord. 1 (1 taxon)
Tortella squarrosa 40.6 70 24 72 60 13 27 72 ? 60 <1 14 <1 20 42
All. 1.1 (1 taxon)
Flexitrichum gracile 32.8 48 24 61 <1 <1 30 61 ? <1 <1 <1 <1 30 33
All. 1.2 (8 taxa)
Cladonia foliacea 7.8 13 5 <1 60 <1 6 <1 ? 60 <1 <1 <1 <1 17
Didymodon acutus 25.0 30 22 22 60 <1 27 22 ? 60 <1 <1 <1 40 8
Lathagrium cristatum 1.6 4 <1 <1 20 <1 <1 <1 ? 20 <1 <1 <1 <1 <1
Pseudocrossidium hornschuchianum 1.6 4 <1 <1 20 <1 <1 <1 ? 20 <1 <1 <1 <1 <1
Scytinium schraderi 1.6 4 <1 <1 20 <1 <1 <1 ? 20 <1 <1 <1 <1 <1
Encalypta vulgaris 3.1 4 2 <1 20 <1 3 <1 ? 20 <1 <1 <1 <1 8
Didymodon vinealis 4.7 9 2 6 20 <1 3 6 ? 20 <1 <1 <1 5 <1
Ditrichum pusillum 6.3 9 5 6 20 <1 6 6 ? 20 <1 <1 <1 5 8
Ord. 2 (4 taxa)
Pseudoscleropodium purum 20.3 <1 32 <1 <1 25 33 <1 ? <1 <1 29 <1 40 25
Cladonia rangiformis 26.6 9 37 6 20 13 42 6 ? 20 100 <1 <1 20 83
Eurhynchiastrum pulchellum 10.9 <1 17 <1 <1 25 15 <1 ? <1 <1 29 <1 20 8
Fissidens dubius 18.8 4 27 6 <1 13 30 6 ? <1 100 <1 100 25 33
All. 2.1 (2 taxa)
Calliergonella cuspidata 20.3 <1 32 <1 <1 50 27 <1 ? <1 100 43 <1 35 17
Weissia controversa 23.4 17 27 17 20 50 21 17 ? 20 100 43 100 25 8
Assoc. 2.1.2 (6 taxa)
Oxyrrhynchium hians 6.3 4 7 6 <1 38 <1 6 ? <1 <1 43 <1 <1 <1
Fissidens taxifolius 14.1 4 20 6 <1 38 15 6 ? <1 <1 43 <1 25 <1
Brachytheciastrum velutinum 1.6 <1 2 <1 <1 13 <1 <1 ? <1 <1 14 <1 <1 <1
Brachythecium rutabulum 1.6 <1 2 <1 <1 13 <1 <1 ? <1 <1 14 <1 <1 <1
Plagiomnium undulatum 1.6 <1 2 <1 <1 13 <1 <1 ? <1 <1 14 <1 <1 <1
Weissia condensa 3.1 4 2 6 <1 13 <1 6 ? <1 <1 14 <1 <1 <1
All. 2.2 (6 taxa)
Entodon concinnus 12.5 <1 20 <1 <1 <1 24 <1 ? <1 <1 <1 <1 20 33
Abietinella abietina 18.8 9 24 11 <1 <1 30 11 ? <1 <1 <1 <1 30 33
Enchylium tenax 7.8 <1 12 <1 <1 <1 15 <1 ? <1 <1 <1 <1 20 8
Cladonia convoluta 15.6 9 20 11 <1 <1 24 11 ? <1 <1 <1 <1 20 33
Thuidium assimile 6.3 <1 10 <1 <1 <1 12 <1 ? <1 <1 <1 <1 10 17
Cladonia cariosa 4.7 <1 7 <1 <1 <1 9 <1 ? <1 <1 <1 <1 10 8
Assoc. 2.2.2 (4 taxa)
Barbula unguiculata 6.3 <1 10 <1 <1 <1 12 <1 ? <1 <1 <1 <1 20 <1
Campyliadelphus chrysophyllus 20.3 13 24 17 <1 13 27 17 ? <1 <1 14 <1 40 8
Rhytidiadelphus squarrosus 3.1 <1 5 <1 <1 <1 6 <1 ? <1 <1 <1 <1 10 <1
Thuidium delicatulum 3.1 <1 5 <1 <1 <1 6 <1 ? <1 <1 <1 <1 10 <1
Assoc. 2.2.3 (23 taxa)
Exsertotheca crispa 14.1 <1 22 <1 <1 <1 27 <1 ? <1 <1 <1 <1 15 50
Ptychostomum capillare aggr. 12.5 4 17 <1 20 <1 21 <1 ? 20 <1 <1 <1 5 50
- Ptychostomum capillare 7.8 4 10 <1 20 <1 12 <1 ? 20 <1 <1 <1 5 25
- Ptychostomum elegans 6.3 <1 10 <1 <1 <1 12 <1 ? <1 <1 <1 <1 <1 33
Tortella tortuosa 23.4 17 27 17 20 <1 33 17 ? 20 <1 <1 <1 20 58
Hypnum cupressiforme 28.1 17 34 17 20 13 39 17 ? 20 <1 14 <1 30 58
Cetraria islandica 3.1 <1 5 <1 <1 <1 6 <1 ? <1 <1 <1 <1 <1 17
Lophocolea heterophylla 3.1 <1 5 <1 <1 <1 6 <1 ? <1 <1 <1 <1 <1 17
Tortella inclinata 7.8 9 7 11 <1 <1 9 11 ? <1 <1 <1 <1 <1 25
Bryum argenteum 4.7 <1 7 <1 <1 <1 9 <1 ? <1 <1 <1 <1 5 17
[…]
Other species (class character species and companion species)
Ctenidium molluscum 43.8 35 49 44 <1 38 52 44 ? <1 100 29 <1 55 50
Homalothecium lutescens 42.2 35 46 44 <1 63 42 44 ? <1 100 57 <1 40 50
Syntrichia ruralis aggr. 12.5 13 12 11 20 <1 15 11 ? 20 <1 <1 <1 5 33
[…]
Table 5.

Climatic structural, ecological and diversity characteristics of the orders and alliances within the Festuco-Brometea. The p-values and significance levels refer to ANOVAs.

Parameter Alliances p-value Sig.
1.1 1.2 2.1 2.2
Total number of relevés 52 87 40 160
Number of relevés from EDGG FW 18 5 8 33
Mean ± SD Mean ± SD Mean ± SD Mean ± SD
Parameters calculated for all relevés
Geographical and climatic parameters
Elevation [m a.s.l.] 602±151 1030±215 561±139 912±273 <0.001 ***
Mediterranity index 0.83±0.19 0.6±0.12 0.91±0.15 0.58±0.15 <0.001 ***
Annual mean temperature [°C] 11.9±1.0 9.9±1.0 12.1±0.7 10.0±1.5 <0.001 ***
Mean annual precipitation [mm] 1025±205 1287±210 920±167 1346±27.0 <0.001 ***
Parameters calculated for relevés from EDGG Field Workshop
Vegetation structure
Cover vegetation total [%] 74±27 68±16 91±7 85±14 0.033 *
Cover shrub layer [%] 4±4 0±0 1±2 0±1 <0.001 ***
Cover herb layer [%] 69±22 62±15 79±26 81±16 0.068 .
Cover cryptogam layer [%] 15±17 9±7 34±32 14±12 0.021 *
Cover litter [%] 11±13 3±4 26±27 5±7 0.001 **
Herb layer maximum height [cm] 77±32 38±15 86±33 58±27 0.005 **
Species richness
Species richness (total) 48.2±10.1 50.6±1.5 55.3±17.9 59.8±15.4 0.041 *
Species richness (vascular plants) 42.9±8.9 46.0±3.8 50.6±16.8 50.5±12.2 0.151 n.s
Species richness (cryptogams) 5.3±2.7 4.6±2.6 4.6±3.0 9.4±5.7 0.004 **
Species richness (bryophytes) 4.7±2.4 3.4±2.1 4.5±2.9 8.0±4.8 0.007 **
Species richness (lichens) 0.6±0.8 1.2±0.8 0.1±0.4 1.4±1.5 0.029 *
Topography
Southing (cosine of aspect) -0.1±0.7 0.8±0.2 -0.5±0.6 -0.5±0.5 <0.001 ***
Inclination [°] 19±11 14±5 11±7 16±15 0.563 n.s
Maximum microrelief [cm] 7±4 9±7 7±7 11±9 0.240 n.s
Soil parameters
Soil depth mean [cm] 14±6 8±5 21±9 17±9 0.034 *
Soil depth CV 48±26 100±82 35±29 46±35 0.020 *
Cover rocks and stones [%] 6±11 9±13 1±4 8±16 0.600 n.s
Cover gravel [%] 10±21 15±17 0±0 3±10 0.112 n.s
Cover fine soil [%] 84±26 76±18 99±4 89±22 0.261 n.s
Coarse fragments [%] 17±15 30±25 30±19 22±16 0.278 n.s
Fine fragments < 2mm [%] 83±15 70±25 70±19 78±16 0.278 n.s
pH 7.65±0.37 7.31±0.86 7.32±0.36 7.52±0.38 0.229 n.s
Electrical conductivity [µS/cm] 188±60 213±141 225±103 261±80 0.031 *
CaCO3 [%] 42.9±9 27.3±23.2 17.9±11.6 19.5±19 <0.001 ***
Organic matter [%] 0.8±0.3 1.8±1.5 1.3±0.4 1.6±0.8 0.001 **
Table 6.

Ecological characteristics of the associations within the Festuco-Brometea. The p-values and significance levels refer to ANOVAs.

Parameter Association p-values Sig.
1.1.1 1.2.1 1.2.2 2.1.1 2.1.2 2.2.1 2.2.2 2.2.3
Total number of relevés 52 25 61 14 26 12 78 69
Elevation [m a.s.l.] 602 1113 989 578 552 800 797 1060 <0.001 ***
Mediterraneity index 0.83 0.61 0.59 0.89 0.91 0.57 0.64 0.51 <0.001 ***
Annual mean temperature [ºC] 11.8 9.8 9.9 12.1 12.1 10.5 10.5 9.4 <0.001 ***
Mean annual precipitation [mm] 1025 1242 1302 905 928 1369 1258 1445 <0.001 ***

The NMDS analysis in Figure 8 shows a clear separation of this order 1 in the upper left part of the diagram. There is also a clear segregation of the alliances. Alliance 1.1 is associated with mediterraneity and high temperatures and alliance 1.2 with elevation and precipitation.

Figure 8. 

NMDS ordination of relevés from Festuco-Brometea. Eigenvalues: Axis 1 – 0.4308, Axis 2 – 0.3302, Axis 3 (not shown) – 0.2389. Med stands for Mediterraneity Index.

The order 2 was defined by Briza media subsp. media, Cynosurus cristatus, Lotus corniculatus, Trifolium ochroleucon and T. pratense subsp. pratense, as diagnostic species (Table 4). It was divided into two alliances. Alliance 2.1 grouped relevés that develop in more Mediterranean areas with lower mean annual precipitation and some of its diagnostic species were Arrhenatherum elatius, Blackstonia perfoliata, Brachypodium phoenicoides, Centaurea jacea and Schedonorus arundinaceus subsp. fenax. Relevés from more humid areas were classified in alliance 2.2, that presented Achillea millefolium subsp. millefolium, Agrostis capillaris, Brachypodium rupestre and Festuca microphylla among its diagnostic species. These two alliances are also clearly separated in the ordination diagram along the mediterraneity and precipitation gradients (Figure 8).

Inside the alliance 2.1 two groups were distinguished. Each one was related to one association previously described according to the analysis of their types: group 2.1.1 to the association Prunello-Plantaginetum serpentinae and group 2.1.2 to the association Carduncello-Brachypodietum phoenicoidis.

Finally, alliance 2.2 was split into three groups corresponding to the associations Helictotricho-Seslerietum hispanicae, Calamintho-Seselietum montani and Carici-Teucrietum pyrenaici according to the position of their type relevés. The latter is mainly distributed in the calcareous Cantabrian and Pyrenean mountains (Figure 9) and was correlated with the highest elevations and annual precipitation values (Figure 8).

Figure 9. 

Location of the relevés from the class Festuco-Brometea: Order 1 (left) and Order 2 (right).

Site conditions and biodiversity of the different vegetation units

The alliance 1.2 is distributed in the highest elevations but also shows by far the highest values of southing; alliance 2.2 is also found in high elevations, and both share lower mediterraneity values compared to alliances 1.1 and 2.1; the two latter alliances show similar values of high temperature and low precipitation but 2.1 occurs in the most thermic and less rainy areas (Table 5, Figure 10). Differences are not so clear in the case of soil carbonate content, although alliance 1.1 shows the highest mean. Regarding structural parameters, the biggest differences amongst alliances are in their shrub layer cover, with highest values for alliance 1.1 (Table 5). At association level, Figure 11 shows that 2.2.3 is found at higher elevations than the other two associations within the alliance, reaching similar elevations as the two associations in alliance 1.2, and shows the lowest mediterraneity values. Association 2.1.2 is found at the lowest elevations and shows the highest mediterraneity, although the lowest precipitation corresponds to its sister association 2.1.1 (Table 6).

Figure 10. 

Comparison of four ecological variables among the four alliances. For elevation and Mediterraneity Index, all relevés were analysed, whereas for the rest of variables only relevés from EDGG Field Workshop were used. Letters represent homogeneous groups (at α = 0.05) according to Tukey’s post-hoc test following a significant ANOVA.

Figure 11. 

Comparison of elevation and Mediterraneity Index among the associations using all relevés from Festuco-Brometea. Letters represent homogeneous groups (at α = 0.05) according to Tukey’s post-hoc test following a significant ANOVA.

The total species richness is similar among the different alliances, as well as richness of vascular plants and lichens (Figure 12). On the contrary, alliance 2.2 outstands by its high bryophyte richness (Figure 12).

Figure 12. 

Comparison of species richness divided into four groups (total species, vascular plants, bryophytes and lichens) among the four alliances in Festuco-Brometea using the relevés from EDGG Field Workshop. Letters represent homogeneous groups (at α = 0.05) according to Tukey’s post-hoc test following a significant ANOVA.

Description of the Festuco-Brometea associations

Association 1.1.1 – Thymelaeo ruizii-Aphyllanthetum monspeliensis

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 13)

Characterisation: Grasslands usually growing on the middle part of slopes, characterised by the dominance of Brachypodium retusum and Bromopsis erecta subsp. erecta. Typical Mediterranean grasses such as Brachypodium retusum, B. phoenicoides, Dactylis glomerata subsp. hispanica, Festuca marginata subsp. andres-molinae and Helictochloa bromoides, and chamaephytes as Helianthemum apenninum subsp. apenninum, Lavandula latifolia and Thymus vulgaris subsp. vulgaris are frequent in this association. In addition, typical species of submediterranean and temperate grasslands are also common: Carex humilis, Koeleria vallesiana, Plantago lanceolata, Potentilla tabernaemontani, Sanguisorba minor, and Teucrium pyrenaicum.

Figure 13. 

Photo plate showing typical stands of the associations included in order 1 of the Festuco-Brometea. A Thymelaeo ruizii-Aphyllanthetum monspeliensis, A1 Overview, A2 Orchis papilionacea, endangered in Navarre; B Jurineo humilis-Festucetum hystricis, B1 Festuca hystrix, B2 Anthyllis montana; C Helianthemo incani-Koelerietum vallesianae, C1 Festuca rectifolia, C2 overview. Photos: A. Berastegi (A2, B1, B2, C1); J. Dengler (A1, C2).

Ecology and distribution: These grasslands are typical of temperate submediterranean transitional areas, at elevations between 400 to 1,100 m a.s.l. The sampled stands are grazed or recently abandoned. They are distributed in the middle part of Navarre region, as serial stages of Quercus faginea, Q. pubescens and Q. rotundifolia forests, and main land use are the cereal crops. They are usually found in carbonate soils developed on marls, limestones, flysch, conglomerates and sandstones, in the meso-supramediterranean and mesotemperate-supratemperate sub-humid to humid belts (Berastegi et al. 2005).

Syntaxonomy: This unit matches quite well with the association Thymelaeo ruizii-Aphyllanthetum monspeliensis, described from the submediterranean central areas in Navarre by Braun-Blanquet (1966) as a dwarf-shrub community. However, Berastegi (2013) did not sample communities of the typical stands rich in dwarf shrubs, and our dataset only includes relevés of the subassociation brachypodietosum retusi. Therefore, the identity of this unit is mostly based on this subassociation dominated by hard-leaved grasses (Brachypodiun retusum, Helictochloa bromoides) and other hemicryptophytes such as Bromopsis erecta subsp. erecta, Carex flacca subsp. flacca, C. humilis, Helictochloa pratensis subsp. iberica and Sanguisorba minor aggr. (Berastegi et al. 2005). Although the type relevé assigned by Braun-Blanquet was also placed by the expert system in the same cluster, we would like to acknowledge that it is only one relevé and thus that the identity of this unit with the whole Thymelaeo-Aphyllanthetum is only provisional. Chamaephyte-rich stands should be included in new analyses to draw a final conclusion.

Association 1.2.1 – Jurineo humilis-Festucetum hystricis

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 13)

Characterisation: These grasslands grow on ridges and flat summit areas that are very windy, in mountain ranges usually above 900 m a.s.l. located in the transition between temperate and Mediterranean climates, in areas where cryoturbation phenomenon usually occurs. Carex humilis, Helianthemum canum subsp. canum and Koeleria vallesiana show a very high constancy in these open grasslands, but they are characterised by species like Anthyllis montana, Arenaria grandiflora subsp. grandiflora, Festuca hystrix, Jurinea humilis and Klasea nudicaulis, most of them typical of the high Mediterranean mountains.

Ecology and distribution: These communities can be found at elevations between 650 and 1,350 m a.s.l., although more commonly above 900 m, in the supramediterranean and supratemperate subhumid-humid belts (Berastegi 2013). They grow on different calcareous rocks such as limestones, calcarenites, marl limestones and conglomerates, on very windy ridges and flat summit areas. Due to the landforms and the elevation at which they are found, the soils are usually stony due to the disintegration processes of the parent rock. Although the ombrotype of this area, e.g., the humidity type, is subhumid to humid, water availability for plants is very low, due to the low water retention capacity of the soils. They are often permanent natural communities, but they may also represent an initial successional stage, colonizing eroded soils after the elimination of more mature stages of the vegetation series in which they are integrated: Fagus sylvatica, Quercus pubescens and Q. rotundifolia series.

Syntaxonomy: This unit fits quite well with the association Jurineo humilis-Festucetum hystricis. Berastegi (2013) included these rocky grasslands in the class Festuco-Ononidetea, order Festuco-Poetalia ligulatae and alliance Plantagini-Thymion mastigophori, due to their affinity to the communities of the associations Koelerio vallesianae-Thymetum mastigophori García-Mijangos et al. 1994 and Festuco hystricis-Genistetum eliassennenii García-Mijangos et al. 1994 from submediterranean territories west of Navarre, where they are widely represented in the landscape (Loidi et al. 1997). These communities reach the central-western area of Navarre, but in specific geographical and ecological conditions, interspersed among other communities with which they share many species. For this reason, they do not achieve enough differential characteristics in the classification analysis to be considered in a different phytosociological class. It is therefore provisionally proposed that they should be included in the Festuco-Brometea, at least in Navarre context.

Association 1.2.2 – Helianthemo incani-Koelerietum vallesianae

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 13)

Characterisation: These communities are dominated by dry grassland species such as Carex humilis, Coronilla minima, Festuca rectifolia, Helianthemum canum subsp. canum, Helictochloa pratensis subsp. iberica, Koeleria vallesiana, Potentilla tabernaemontani, or Thymus praecox. Typical species of meso-xeric grasslands such as Bromopsis erecta subsp. erecta or Carthamus mitissimus are also common. From a physiognomic point of view, they are characterised by being short grasslands, with a cover of around 70-90%, in which some creeping chamaephytes can be important.

Ecology and distribution: The association represents pastures which are subject to intense livestock use, mainly by sheep, especially in the summer period. It occurs on different types of carbonate substrates (limestones, calcarenites, conglomerates, flysch), although mainly on limestone. They develop in the mountain ranges of the transition between the Atlantic and Mediterranean regions, also reaching the westernmost Pyrenean mountains, mostly in the montane belt.

Syntaxonomy: This unit matches well with the association Helianthemo incani-Koelerietum vallesianae, which was originally included in the class Festuco-Ononidetea, order Ononidetalia striatae, alliance Genistion occidentalis (Berastegi 2013), due to the floristic and ecological affinities to other rocky dry grasslands also included in this alliance. However, we would like to acknowledge that Genistion occidentalis originally included cushion shrub communities from Cantabrian mountains and Western Pyrenees (Díaz and Fernández-Prieto 1994), and only recently rocky dry grasslands from the Basque-Cantabrian mountains (Helictotricho-Seslerietum hispanicae and Carici-Teucrietum pyrenaici) were moved to this alliance and consequently to the class Festuco-Ononidetea (Rivas-Martínez 2011) from the class Festuco-Brometea where they had been previously placed (Rivas-Martínez et al. 1991a).

Association 2.1.1 – Prunello hyssopifoliae-Plantaginetum serpentinae

(relevès in Suppl. material 14; distribution in Figure 9)

Characterisation: These communities are characterised by species like Festuca capillifolia, Jasonia tuberosa, Plantago maritima subsp. serpentina or Prunella hyssopifolia. Other species with high frequency are Blackstonia perfoliata, Carex flacca subsp. flacca, Centaurea jacea or Dorycnium pentaphyllum subsp. pentaphyllum.

Ecology and distribution: They are typical of the submediterranean climate and can be found at elevations from 410 to 1,000 m a.s.l., in the colline and montane belts. These communities develop in micro-depressions in loamy or clayey soils, which, due to their impermeable nature, are subject to temporary waterlogging. During the rainy season, these areas can become flooded, while in periods of strong sunshine they dry out completely. They are relatively frequent in the areas of blue-grey loams in the central part of Navarre, as serial stages of Quercus pubescens and Q. faginea forests, and main land use are the cereal crops.

Syntaxonomy: This unit matches quite well with the Prunello hyssopifoliae-Plantaginetum serpentinae association, originally placed in the class Molinio-Arrhenatheretea, although as a quite deviant community from the alliance Deschampsion mediae that often occurs in mosaic with meso-xeric grasslands; thus, typical dry grassland species are common (Biurrun 1999; Berastegi 2013).

Association 2.1.2 – Carduncello mitissimi-Brachypodietum phoenicoidis

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 14)

Characterisation: Grasslands growing usually on the middle or bottom part of slopes, characterised by Blackstonia perfoliata, Brachypodium phoenicoides (including its hybrid with B. rupestre), Bromopsis erecta subsp. erecta, Carex flacca subsp. flacca, Eryngium campestre or Phleum pratense. Some other typical Festuco-Brometea species also occur: Carthamus mitissimus, Centaurea jacea, Ranunculus bulbosus subsp. bulbosus or Trifolium ochroleucon. Species of the class Molinio-Arrhenatheretea are also common, including Lotus corniculatus, Plantago lanceolata, Trifolium campestre and T. pratense.

Figure 14. 

Photo plate showing typical stands of the associations included in order 2 of the Festuco-Brometea. A Carduncello mitissimi-Brachypodietum phoenicoidis; B Helictotricho cantabrici-Seslerietum hispanicae; C Calamintho acini-Seselietum montani, D Carici ornithopodae-Teucrietum pyrenaici. Photos: J. Dengler (A, C, D); A. Berastegi (B).

Ecology and distribution: These dry grasslands are typical for the submediterranean climate type and can be found at elevations between 400 and 1,040 m a.s.l., in the supramediterranean and mesotemperate belts. They appear on clayey soils developed from calcareous materials (marl and limestone). They are distributed in the middle area of Navarre region, as serial stages of Quercus pubescens and Q. faginea forests, and main land use are the cereal crops. The sampled stands are grazed with low intensity or have been recently abandoned.

Syntaxonomy: This unit matches well with the association Carduncello mitissimi-Brachypodietum phoenicoidis, originally included in the order Brachypodietalia phoenicoidis (Berastegi 2013).

Association 2.2.1 – Helictotricho cantabrici-Seslerietum hispanicae

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 14)

Characterisation: These communities, dominated by the grasses Brachypodium rupestre, Helictotrichon cantabricum or Sesleria autumnalis, develop on rocky, steep slopes on limestone, usually with large crevices. In addition to the abovementioned species, it is common to find species such as Bromopsis erecta subsp. erecta, Carex flacca subsp. flacca, Dactylis glomerata, Galium pumilum, Teucrium pyrenaicum or Vincetoxicum hirundinaria subsp. intermedium. Some scrub species such as Dorycnium pentaphyllum subsp. pentaphyllum, Erica vagans or Genista hispanica subsp. occidentalis are also present, sometimes with relevant cover.

Ecology and distribution: These rocky grasslands are typical for the temperate climate and can be found at elevations between 460 and 1,050 m a.s.l., in the colline and montane belts These communities develop mainly in the context of the series of Quercus ilex, Fagus sylvatica and Quercus pubescens. However, their main role is as a permanent natural community on steep calcareous slopes.

Syntaxonomy: This unit roughly matches with the association Helictotricho cantabrici-Seslerietum hispanicae described by Braun-Blanquet (1967) in more atlantic areas of nearby Basque Country. Originally placed in the Potentillo-Brachypodion pinnati (Braun-Blanquet 1967; Rivas-Martínez et al. 1991a), the Spanish checklist of phytosociological syntaxa (Rivas-Martínez 2011) included it in the alliance Genistion occidentalis, therefore in the class Festuco-Ononidetea, although, it has also been assigned to the alliance Bromo erecti-Teucrion pyrenaici Rivas-Mart. et al. 1997 (Loidi et al. 1997).

Association 2.2.2 – Calamintho acini-Seselietum montani

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 14)

Characterisation: Basophilous grasslands characterised by Brachypodium rupestre, Briza media subsp. media, Bromopsis erecta subsp. erecta, Carex flacca subsp. flacca, Lotus corniculatus or Plantago media. Some other taxa typical in these communities are Carthamus mitissimus, Helictochloa pratensis subsp. iberica, Linum catharticum subsp. catharticum, Potentilla tabernaemontani, Ranunculus bulbosus subsp. bulbosus, Thymus praecox and Trifolium ochroleucon. Species such as Achillea millefolium or Trifolium pratense are also common within the most mesic stands.

Ecology and distribution: These meso-xeric grasslands are typical for the temperate climate with submediterranean features and can be found at elevations between 230 and 1,400 m a.s.l., in the colline and montane belts. They develop on more or less deep soils, as serial stages of Fagus sylvatica and Quercus pubescens forests.

Syntaxonomy: This unit matches quite well with the association Calamintho acini-Seselietum montani described by Braun-Blanquet (1967) from temperate areas in Navarran inner valleys. In the Atlantic valleys in Navarre and nearby Basque Country it is replaced by the association Seseli cantabrici-Brachypodietum rupestris Br.-Bl. 1967 corr. Rivas-Mart. et al. 1984 (Rivas-Martínez et al. 1991a), linked to a more oceanic and humid climate. However, we could not reproduce this unit in our classification, as we had very sparse data from these Atlantic valleys.

Association 2.2.3 – Carici ornithopodae-Teucrietum pyrenaici

(relevès in Suppl. material 14; distribution in Figure 9; photos in Figure 14)

Characterisation: These grasslands are characterised by species such as Clinopodium alpinum subsp. pyrenaeum, Festuca rectifolia, Helictochloa pratensis subsp. iberica, Seseli montanum subsp. montanum or Teucrium pyrenaicum, and some orophilous plants such as Poa alpina and Vicia pyrenaica. Typical elements of Festuco-Brometea such as Bromopsis erecta subsp. erecta, Carex caryophyllea, Helianthemum nummularium, etc. also occur, as well as others of Nardetea and Molinio-Arrhenatheretea such as Festuca microphylla, Lotus corniculatus or Plantago lanceolata.

Ecology and distribution: They are typical for the temperate climate and can be found at elevations between 560 and 1,720 m a.s.l., mostly in the montane belt. They usually grow on shallow soils (rendzina) developed on limestones, in the beech forest belt, and main land use is summer grazing (transterminant herds).

Syntaxonomy: This unit roughly matches with the association Carici ornithopodae-Teucrietum pyrenaici described by Loidi (1983), although it also includes some relevés originally included in Festucion scopariae and an important number of relevés originally classified in Helianthemo incani-Koelerietum vallesianae. Originally placed in the alliance Potentillo-Brachypodion pinnati (Loidi 1983; Rivas-Martínez et al. 1991a), the Spanish checklist of phytosociological syntaxa (Rivas-Martínez 2011) included it in the alliance Genistion occidentalis, therefore in the class Festuco-Ononidetea, although it has also been assigned to the alliance Bromo erecti-Teucrion pyrenaici Rivas-Mart. et al. 1997 (Loidi et al. 1997).

Discussion

Delimitation of the grassland classes

Although 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). Dry and rocky grasslands and dwarf-shrub communities have been traditionally assigned to the class Festuco-Ononidetea and those scrublands with a more Mediterranean character to Ononido-Rosmarinetea. Nevertheless, we could not recognise any of these two classes in Navarre in the context of the grasslands. Rather, they would remain within the communities dominated by dwarf shrubs and chamaephytes, while the communities dominated by grasses would belong to Festuco-Brometea or Elyno-Seslerietea. This new arrangement would tally with the European perspective of placing rocky grasslands in Festuco-Brometea (Willner et al. 2017, 2019; Dengler et al. 2020b), although their distinction from the remaining units in the classes Festuco-Ononidetea and Ononido-Rosmarinetea mentioned above, is still to be clarified.

The class Festuco-Ononidetea was proposed by Rivas-Martínez et al. (1991b) to separate grasslands rich in tussock grasses and dwarf shrubs with submediterranean continental supra-oromediterranean distribution from the communities dominated by nanophanerophytes and dwarf shrubs with broad Mediterranean distribution of the class Rosmarinetea officinalis Rivas-Mart. et al. 2002. The authors recognised two orders within the class, Ononidetalia striatae and Festuco hystricis-Poetalia ligulatae. Subsequently, Mucina et al. (2016) also included in Festuco-Ononidetea the order Erysimo-Jurineetalia bocconei, which includes submediterranean xeric calcicolous grasslands on skeletal soils of the Apennine Peninsula and the oromediterranean belt of Sicily. Nevertheless, the assignment of the orders Ononidetalia and Erysimo-Jurineetalia to the class Festuco-Ononidetea has been controversial (Bardat et al 2004; Biondi et al. 2014). In the Iberian Peninsula, the order Ononidetalia striatae has a Pyrenean and Cantabrian distribution, encompassing seven alliances that include a very heterogenous set of communities: dry grasslands, dwarf shrublands and cushions, occurring from the sea level to the subalpine belt (Rivas-Martínez 2011). According to our results, grasslands of Ononidetalia in Navarre should be included either in Festuco-Brometea or in Elyno-Seslerietea. The full set of communities of this order, including its type alliance Ononidion striatae, should be analysed together with dry grasslands in order to decide on its potential complete integration in Festuco-Brometea.

The class Elyno-Seslerietea gathers alpine and subalpine calcicolous swards of the nemoral mountain ranges of Europe. In Navarre, they belong to the Alpine-Pyrenean order Seslerietalia caeruleae and the alliance Primulion intricatae (Mucina et al. 2016). However, our analyses pose the question whether subalpine grasslands of Festucion scopariae should also be included in this class. Actually, this alliance had been originally included by Braun-Blanquet (1948) in Elyno-Seslerietea, but subsequently Rivas-Martínez et al. (1991b) transferred it to Ononidetalia striatae. Peyre and Font (2011) conducted a syntaxonomic revision by means of numerical analysis of the subalpine and alpine grasslands of the Pyrenees and Cantabrian Mountains and concluded that Festucion scopariae should be included in the order Seslerietalia caeruleae, even though it contains some thermophilous species. Our results also support the reclassification of Festucion scopariae into the class Elyno-Seslerietea as it presents a number of species of this class (Euphrasia salisburgensis, Gentiana verna subsp. verna, Helictotrichon sedenense subsp. sedenense, Trifolium thalii), which differentiates them from the rest of the Festuco-Ononidetea communities.

As regards the class Carici-Kobresietea bellardii, although our analysis included these communities in Elyno-Seslerietea, we kept it as a separate class, as it was only represented by two relevés in our dataset. Actually, these cryophytic alpine grasslands are very scarce in Navarre, so our geographic scope is not suitable to decide on the separation or grouping of both classes.

The class Nardetea strictae was defined as secondary oligotrophic grasslands and groups mesophilous or acidophilous, fairly grazed, tussock grasslands dominated by Nardus stricta from the montane to alpine belts with humid and hyper-humid ombroclimate (Rivas Goday and Rivas-Martínez 1963). Our relevés were included by Berastegi (2013) in the alliances Violion caninae and Carici macrostylidi-Nardion strictae (sub suballiance Carici-Nardenion strictae), following the classification of Rivas-Martínez (2011). However, the Carici macrostylidi-Nardion, grouping mat-grass chionophilous swards at high elevations of the Pyrenees and the Cantabrian Mountains (Rivas-Martínez et al. 1984) was transferred by Mucina et al. (2016) to the class Juncetea trifidi, within the order Festucetalia spadiceae. This new classification is based on the differentiation of the secondary mat-grass swards growing at low and mid-elevations included within the class Nardetea, from the primary oligotrophic pastures/grasslands occurring at high elevations, placed within the Juncetea trifidi (Mucina et al. 2016). Further analyses supported the separation of high and mid-low elevation swards (Rodriguez-Rojo et al. 2020), although Gavilán et al. (2017) included Nardus stricta grasslands from high elevations in the Pyrenees in the Festucion eskiae alliance, not in Carici macrostylidi-Nardion. Our analyses do not support the separation of low and high elevation swards, as all relevés originally assigned to the alliances Violion caninae and Carici macrostylidi-Nardion were grouped in the same cluster. In Navarre, the class Juncetea trifidi according to Rivas-Martínez (2011, as Caricetea curvulae) is represented by the association Carici pseudotristis-Festucetum eskiae, within the alliance Festucion eskiae. These communities have a central Pyrenean distribution and only occasionally reach the highest siliceous peaks in Navarre (Lakora Mountain). The scarcity of data from this alliance does not allow us to establish a clear differentiation between the classes Nardetea and Juncetea trifidi in the territory, as only one relevé from Juncetea trifidi was available, which was of course included in Nardetea. A more in-depth study would be necessary to decide definitively in this respect, since the high presence of acidophilous species in the communities of Violion caninae, Carici macrostylidi-Nardion and Festucion eskiae (Berastegi 2013) determines their grouping compared to the rest of the grasslands and pastures analysed in the context of this study.

According to our results, the association Merendero-Cynosuretum should also be included in the class Nardetea strictae. This association was originally included in the alliance Cynsurion cristati of the Molinio-Arrhenatheretea class (Tüxen and Oberdorfer 1958), although the high constancy of Nardus stricta and Danthonia decumbens is noteworthy. These pastures originate from the oligotrophic grasslands after intense grazing (Berastegi 2013). The position of this association within Nardetea would be justified by the high presence of acidophilous species diagnostic of this group, such as Festuca microphylla, Galium saxatile and Polygala serpyllifolia. However, they are enriched by species of the alliance Cynosurion due to livestock pressure.

Our analysis included relevés previously classified in the alliance Sedion pyrenaici from the class Sedo-Scleranthetea in Nardetea strictae. However, we have to consider the reduced context of our study, so we kept this class as a separate unit. In Navarre, these communities shaped by succulent species and dwarf chamaephytes growing on siliceous lithosols and rock surfaces (Rivas-Martínez et al. 2002) develop in montane and subalpine areas forming mosaics with grasslands of Nardetea strictae. Consequently, they share some acidophilous plants such as Agrostis curtisii, Festuca microphylla and Galium saxatile.

Molinio-Arrhenetheretea is the most diverse class in Navarre regarding the number of associations. Berastegi (2013) recognised twelve alliances grouped within four orders. Although some associations were not well represented in our data, especially the most hygrophilous ones, the TWINSPAN analysis did reproduce a structure with three branches interpreted as corresponding to the orders Arrhenatheretalia elatioris, Molinietalia caeruleae and Holoschoenetalia. The only changes regarding this class are the new positions of the associations Merendero-Cynosuretum (Cynosurion, Arrhenatheretalia) and Prunello-Plantaginetum serpentinae (Deschampsion mediae, Holoschoenetalia). We suggest moving the former to the class Nardetea strictae, as explained above, while the latter should be placed in Festuco-Brometea, as has been also explained in the results section.

The class Lygeo-Stipetea gathers Mediterranean pseudo-steppes on calcareous substrates and relict Mediterranean steppes on deep clayey soils (Mucina et al. 2016). In Navarre this class encompasses communities dominated by Lygeum spartum on the one hand and Brachypodium retusum grasslands on the other (Berastegi 2013). The former develops on the bottom of slopes receiving regular downslope input of fine materials (silt, clay) and can tolerate short periods of hydromorphy. Lygeum spartum communities are characterised by the co-occurrence of many annual species (Asterolinon linum-stellatum, Filago pyramidata, Linum strictum, Trachynia distachya) (Marcenò et al. 2019). However, the delimitation of Brachypodium retusum grasslands is another unresolved syntaxonomic issue (Apostolova et al. 2014). Two associations belonging to two different classes are recognised in the territory (Berastegi 2013), which is also reflected in our results. Within Lygeo-Stipetea, the association Ruto angustifolio-Brachypodietum retusi groups the typically Mediterranean grasslands of the Ebro valley (Braun-Blanquet and Bolòs 1958). The other syntaxon including grasslands rich in Brachypodium retusum is Thymelaeo-Aphyllanthetum brachypodietosum retusi, which was classified in Festuco-Brometea and is thus discussed in the next section.

Our analyses placed relevés of the classes Poetea bulbosae and Stipo-Trachynietea distachyae in Lygeo-Stipetea. However, our dataset contained only a small number of relevés from these classes and thus we cannot make any decision about the grouping of these classes within Lygeo-Stipetea. Therefore, we kept both classes as independent units.

Subdivision of the Festuco-Brometea

In Navarre, the class Festuco-Brometea is composed of dry grasslands dominated by hemicryptophytes that develop on non-hygromorphic soils in temperate and submediterranean climates (Berastegi 2013). According to our results, the class Festuco-Brometea in Navarre includes, besides the associations previously assigned to this class (Calamintho-Seselietum montani and Carduncello-Brachypodietum phoenicoidis), several associations that had been included in the class Festuco-Ononidetea striatae (Rivas-Martínez 2011; Berastegi 2013): Carici-Teucrietum pyrenaici, Helianthemo-Koelerietum vallesianae and Helictotricho-Seslerietum hispanicae from the order Ononidetalia striatae, and Jurineo-Festucetum hystricis from the order Festuco-Poetalia ligulatae. Additionally, the association Thymelaeo-Aphyllanthetum monspeliensis, classified in Ononido-Rosmarinetea by the Spanish checklist (Rivas-Martínez 2011) has also been included in Festuco-Brometea, as well as the association Prunello-Plantaginetum serpentinae, previously classified in Molinio-Arrhenatheretea (Rivas-Martínez 2011)

The numerical analysis clearly separates two groups that can be interpreted as two orders. Order 1 groups the more xerophytic relevès with Mediterranean influence which occupy an intermediate position between the orders Brachypodietalia pinnati and the more Mediterranean communities of Festuco-Ononidetea and Ononido-Rosmarinetea. This order would be a vicariant of Astragalo-Potentilletalia and Stipo-Festucetalia pallentis from central-southern Europe (Aćić et al. 2015).

Communities in this order 1 are included in two alliances. Alliance 1 includes the association Thymelaeo-Aphyllanthetum monspeliensis, originally included in the alliance Helianthemo italici-Aphyllanthion monspeliensis (class Ononido-Rosmarinetea) by Braun-Blanquet (1966). Subsequently most Spanish phytosociologists have also placed it there, including the Spanish checklist (Rivas-Martínez 2011), where it sits well due to the high cover of dwarf shrubs in the typical subassociation. A new comprehensive analysis including all basophilous grasslands and dwarf-shrublands from Mediterranean and submediterranean areas in Europe would help us decide not only on the syntaxonomic position of Thymelaeo-Aphyllanthetum, but also on the position of the alliance Helianthemo-Aphyllanthion. Consequently, we put forward the question whether a new alliance and order should be proposed for these grasslands rich in dwarf shrubs which would be transitional to Lygeo-Stipetea and Ononido-Rosmarinetea.

Alliance 2 in this order 1 includes two associations that were previously classified in two different orders of the class Festuco-Ononidetea: Jurineo humilis-Festucetum hystricis in the order Festuco-Poetalia ligulatae and Helianthemo incani-Koelerietum vallesianae in Ononidetalia striatae (Berastegi 2013). These communities contain a number of species diagnostic for perennial rocky calcareous grasslands of subatlantic-submediterranean Europe belonging to the Xerobromion, the Festuco-Bromion or the Artemisio-Dichantion (Chytrý et al. 2020), which justifies their inclusion within Festuco-Brometea. The identity of this alliance also remains unresolved until a comprehensive analysis including all basophilous grasslands and dwarf-shrublands in southern Europe is conducted.

Order 2 is related to Brachypodietalia pinnati and includes grasslands that usually develop in areas with a temperate climate, in well-constituted soils with relatively good water retention capacity and normally high total vegetation cover. Calamintho-Seselietum represents one of the typical associations of this order. This order also includes grasslands growing in rocky steep slopes from areas of high rainfall (Helictotricho-Seslerietum hispanicae and Carici-Teucrietum pyrenaici), as well as dry grasslands from submediterranean areas, but the latter ones are restricted to soils or topographic situations that allow relatively good water retention (Prunello-Plantaginetum serpentinae and Carduncello-Brachypodietum phoenicoidis).

Rocky grasslands from this order 2 (Helictotricho-Seslerietum hispanicae and Carici-Teucrietum pyrenaici) are included in Ononidetalia striatae in the Spanish checklist, but our analysis has shown that they have a strong floristic relationship with grasslands of Brachypodietalia pinnati. In fact, both associations were originally included in this order (Braun-Blanquet 1967; Loidi 1983).

Alliance 2.1, which includes the associations Prunello-Plantaginetum serpentinae and Carduncello-Brachypodietum phoenicoidis in Navarre, could be assigned to the alliance Brachypodion phoenicoidis. More comprehensive analyses would be needed to confirm, as this alliance is distributed along the Western Mediterranean region, and its type association Brachypodietum phoenicoidis Br.-Bl. 1924 was described in Mediterranean France (Rivas-Martínez 2011).

Proposed syntaxonomic scheme for the class Festuco-Brometea in Navarre

Class: Festuco-Brometea Br.-Bl. et Tx. ex Klika et Hadač 1944

Order 1: ???

Alliance 1.1: ???

1.1.1: Thymelaeo ruizii-Aphyllanthetum monspeliensis Br.-Bl. et P. Montserrat in Br.-Bl. 1966

Alliance 1.2: ???

1.2.1: Jurineo humilis-Festucetum hystricis Peralta et al. in Berastegi 2013

1.2.2: Helianthemo incani-Koelerietum vallesianae Berastegi et al. in Berastegi 2013

Order 2: Brachypodietalia pinnati Korneck 1974 nom. cons. propos. (= Brometalia erecti Koch 1926)

Nomenclatural remark: Dengler et al. (2003) proposed to reject the name Brometalia erecti Koch 1926 as nomen ambiguum, and Kuzemko et al. (2014) proposed to conserve the name Brachypodietalia pinnati Korneck 1974. This proposal was also adopted by Mucina et al. (2016), but no formal proposal has been submitted so far.

Alliance 2.1: ???

2.1.1: Prunello hyssopifoliae-Plantaginetum serpentinae F. Prieto et al. ex Biurrun 1999

2.1.2: Carduncello mitissimi-Brachypodietum phoenicoidis García-Mijangos et al. in Berastegi 2013

Alliance 2.2: Potentillo montanae-Brachypodion pinnati Br.-Bl. 1967

2.2.1: Helictotricho cantabrici-Seslerietum hispanicae Br.-Bl. 1967

2.2.2: Calamintho acini-Seselietum montani Br.-Bl. 1967

2.2.3: Carici ornithopodae-Teucrietum pyrenaici Loidi 1983

Biodiversity

Grasslands of Festuco-Brometea showed the highest total species richness, and specifically meso-xeric grasslands of the association Calamintho-Seselietum montani, which have previously been highlighted as species rich grasslands (Dengler et al. 2016b; Boch et al. 2020). However, differences with mesic grasslands are not significant. In fact, only bryophyte richness is significantly higher in Festuco-Brometea than in Molinio-Arrhenatheretea in the Navarran context. This may be due to the continued agricultural extensive management of these secondary mesic grasslands, at least in part of the region, as it has been demonstrated that intensively managed grasslands tend to be species poor (Hilpold et al. 2018). In any case, the high bryophyte richness of Festuco-Brometea grasslands is comparable to that of alpine grasslands of Elyno-Seslerietea, which is the richest vegetation type when both bryophytes and lichens are considered. This significant cryptogam-richness of alpine grasslands was already shown by Dengler et al. (2020c) and has recently been evidenced using a very large dataset by Biurrun et al. (2021). We would also like to highlight the high lichen richness in the Mediterranean grasslands of Lygeo-Stipetea, which is comparable in this respect to Elyno-Seslerietea. Our results show that these Mediterranean grasslands, although being quite species-poor regarding total species richness and richness of vascular plants, host a high proportion of bryophytes and especially lichens, which was already observed by Biurrun et al. (2021).

Relevance of bryophytes and lichens

Up to now vegetation ecologists in the Southern European countries, and particularly in the Mediterranean region, rarely considered bryophytes and lichens as part of the vegetation - unlike many of their colleagues in temperate and boreal Europe. This is reflected by the fact that for example, Rivas-Martínez et al. (2002) in their overview of the syntaxa of the Iberian Peninsula did not list any non-vascular plant species (apart from few Characeae spp. and Sphagnum spp.) as diagnostic for any of the hundreds of syntaxa of the region. Also, Mucina et al. (2016), while listing some bryophytes and lichens as diagnostic for temperate and boreal classes, do not mention any for the Mediterranean classes. Even Dierßen (2001), who characterised the phytosociological prevalences of all European bryophyte species, systematically under-reported their presence in Mediterranean classes. As already highlighted by Guarino et al. (2012) in the report from the EDGG Field Workshop in Sicily, the non-vascular flora of Mediterranean grasslands can be quite rich. In fact, while amongst all grasslands of Navarre, those of the Mediterranean class Lygeo-Stipetea were poorest in vascular plants, they hosted the highest lichen diversity together with the Elyno-Seslerietea. We also found that bryophytes and lichens are not randomly distributed across communities but have clear and often narrow prevalences which makes them equally effective diagnostic species as many vascular plants. All this calls for a better consideration of non-vascular plants in syntaxonomic studies in South European countries.

Conclusions and outlook

The combination of numerical methods allows a standardisation of the classification of grassland types. In fact, with our expert system we could largely reproduce the associations previously recognised in the region. Moreover, some often “diagnostic” species mentioned in the literature could be confirmed by our numerical analyses of a large dataset, while others were not supported by the data. However, at the class level, we found significant deviations from the Iberian syntaxonomic tradition (Rivas-Martínez et al. 2002; Rivas-Martínez 2011) and we propose a new system that matches the Iberian data more appropriately, and is consistent with the European concept of the class Festuco-Brometea. In any case, questions still remain regarding classification at order and alliance level, which can only be solved by means of a comprehensive analysis of all basophilous grasslands and dwarf-shrub communities in southern Europe. This analysis will also allow for the delimitation of the controversial class Festuco-Ononidetea.

Our study provides, for the first time, an electronic expert system for the grasslands of Navarre, which allows a standardised assignment of any new relevé, thus is of enormous value, particularly for practitioners. We provide, also for the first time, a detailed databased characterisation and comparison of the syntaxa in terms of their environmental conditions and biodiversity. We were also able to show that bryophytes and lichens, contrary to past assumptions, are core elements of these grasslands and in particular, the Mediterranean ones of Lygeo-Stipetea, both in terms of biodiversity and of diagnostic species. Therefore, they should also be taken into account in Mediterranean phytosociology.

Once the main five phytosociological classes were differentiated, our study focused on the analysis of the Festuco-Brometea. Therefore, an in-depth analysis based on expert systems of the rest of the classes would be desirable. Moreover, classes whose status could not be resolved due to a small/marginal dataset or due to plot sizes being too small, should be specifically addressed in future studies with better/more data from a larger area.

Finally, it can be emphasised that we have provided important insights from the western part of Europe that complement the extensive studies of Willner et al. (2017, 2019) from Central and Eastern Europe. Thus, we have taken a new step on the pan-European classification of the Festuco-Brometea. With this aim, we acknowledge that these comprehensive analyses would be facilitated if the hierarchical expert system and hierarchical determination of diagnostic species could be directly implemented in JUICE.

Data availability

The vegetation-plot data underlying this study are stored and available in the GrassPlot database (https://edgg.org/databases/GrassPlot; dataset code ES_A; Dengler et al. 2018a, Biurrun et al. 2019), from which they can be requested according to the GrassPlot Bylaws, and in the Vegetation-Plot Database of the University of the Basque Country (BIOVEG) (Biurrun et al. 2012), which is available in the European Vegetation Archive (Chytrý et al. 2016) and the Global Vegetation Database sPlot (Bruelheide et al. 2019) as dataset EU-00-011.

Author contributions

I.G.M, I.B. and A.B. organized the 7th EDGG Field Workshop in Navarre (Spain); as EDGG Field Workshop Coordinator during the Field Workshop, J.D. ensured consistent application of the EDGG methodology, I.G.M. identified the vascular plant species collected during the Field Workshop, J.E. identified the lichens, R.N. identified the bryophytes and added ecological aspects, and O.Y. analysed the soil samples and described methodological aspects; A.B. compiled 839 relevés used in the paper from 1996 to 1999; I.G.M. together with J.D. developed the numerical classification, implemented the expert system and identified the diagnostic species with the collaboration of I.B., A.B., A.K., M.J., and D.V.; M.J. developed the NMDS ordination, I.D. and D.V. analysed differences between syntaxa by means of ANOVAs and J.D. calculated and analysed biodiversity patterns; I.G.M. led the writing of the manuscript with substantial inputs from A.B., I.B. and J.D.; all authors critically revised the manuscript.

Acknowledgements

We are grateful to EDGG and IAVS for financial support for some of the participants. I.G. and I.B. were supported by the Basque Government (IT936‐16). We would like to give special thanks to F. Urra and I. Ibarrola for helping with the organization of the field workshop in Navarre. Thanks to all Field Workshop participants and other helpers who did not opt-in as authors.

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E-mail and ORCID

Itziar Garcia-Mijangos (itziar.garcia@ehu.eus), ORCID: https://orcid.org/0000-0002-6642-7782

Asun Berastegi (aberastg@gan-nik.es), ORCID: https://orcid.org/0000-0003-0456-3305

Idoia Biurrun (Corresponding author, idoia.biurrun@ehu.eus), ORCID: https://orcid.org/0000-0002-1454-0433

Iwona Dembicz (i.dembicz@gmail.com), ORCID: https://orcid.org/0000-0002-6162-1519

Monika JaniŠová (monika.janisova@gmail.com), ORCID: https://orcid.org/0000-0002-6445-0823

Anna Kuzemko (anyameadow.ak@gmail.com), ORCID: https://orcid.org/0000-0002-9425-2756

Denys Vynokurov (denys.vynokurov@gmail.com), ORCID: https://orcid.org/0000-0001-7003-6680

Didem Ambarlı (didem.ambarli@gmail.com), ORCID: https://orcid.org/0000-0001-5589-9373

Javier Etayo (jetayosa@educacion.navarra.es), ORCID: https://orcid.org/0000-0003-0392-0710

Goffredo Filibeck (filibeck@unitus.it), ORCID: https://orcid.org/0000-0002-4187-9467

Ute Jandt (ute.jandt@botanik.uni-halle.de), ORCID: https://orcid.org/0000-0002-3177-3669

Rayna Natcheva (renimoss@bio.bas.bg)

Oktay Yildiz (oktayyildiz@duzce.edu.tr), ORCID: https://orcid.org/0000-0002-8058-4506

Jürgen Dengler (dr.juergen.dengler@gmail.com), ORCID: https://orcid.org/0000-0003-3221-660X