Botanists Move to Safeguard the Name of Europe’s Species-Rich Semi-Dry Grasslands

Some of the most biologically remarkable habitats in Europe may soon receive a small but consequential gift: a stable, officially protected scientific name. In a formal nomenclatural proposal published in the journal Vegetation Classification and Survey, two researchers have asked the governing body of phytosociological nomenclature to conserve the name Brachypodietalia pinnati Korneck 1974, together with a conserved type, for the order of mesoxeric basiphilous grasslands within the class Festuco-Brometea. These are the semi-dry, calcareous grasslands that flourish on nutrient-poor soils across the continent, and they hold a world record: the highest vascular plant species richness ever recorded at grain sizes below 100 square metres. Behind the dry technical language of the proposal lies a decades-long dispute over naming conventions that has real consequences for how ecologists communicate about one of Europe’s most threatened groups of habitats.

The grasslands in question are of outstanding importance both scientifically and for conservation. Because they are low-productivity ecosystems, they resist domination by a few vigorous species and instead support an extraordinary diversity of plants, often dozens of species packed into a single square metre. Yet these formerly widespread habitats are in steep decline throughout Europe, losing both area and quality mainly through agricultural intensification, abandonment of traditional mowing and grazing, and eutrophication from airborne nutrients. The European Red List of Habitats recognises them as semi-dry perennial calcareous grassland, and the refined EUNIS habitat typology places them in category R1A, the semi-dry perennial calcareous grasslands and meadow steppes. A stable name for the order that unites these vegetation types is therefore not an academic nicety but a practical tool for conservation planning, habitat mapping and legal protection.

The scientific problem is rooted in the history of vegetation science itself. Phytosociology, the discipline that classifies plant communities, follows its own rulebook, the International Code of Phytosociological Nomenclature, currently in its fourth edition. Under this code, names of vegetation units are tied to nomenclatural types, typically a characteristic association or alliance, and priority rules determine which name is correct. For most of the twentieth century, the class Festuco-Brometea, which encompasses Europe’s dry and semi-dry grasslands, was divided into geographically defined orders. The order Brometalia erecti, described by W. Koch in 1926 from the Linth Plain on the Swiss Plateau, covered the subatlantic west, while the continental east was assigned to Festucetalia valesiacae, and further geographic orders such as Scorzoneretalia villosae and Helictotricho-Stipetalia were added for the more distal parts of the continent.

Koch’s original concept, however, differed from the way his name came to be used. In his 1926 publication, the alliance Bromion erecti was established with the association Mesobrometum erecti as its holotype, and the order Brometalia erecti was established with Bromion erecti as its holotype. The Mesobrometum erecti clearly belongs to the subatlantic, mesoxeric basiphilous grasslands. In the following decades, though, the concept of Brometalia erecti was narrowed to the subatlantic parts of the class, and in some influential treatments the order was even applied in a sense that excluded its own type, comprising only the xeric Xerobromion. This history of shifting and contradictory usage is precisely why many modern authors regard Brometalia erecti as a nomen ambiguum, an ambiguous name whose continued use invites confusion.

The turning point came from two mid-century botanists. Krausch in 1961 first highlighted that the mesoxeric alliances of the two geographic orders, the Mesobromion erecti and the Cirsio-Brachypodion pinnati, share more floristic commonalities with each other than with their respective xeric counterparts, the Xerobromion erecti and the Festucion valesiacae. Korneck then took the decisive step in 1974, proposing to replace the purely geographic division of the class with a mainly edaphic one, based on soil conditions, and establishing the order Brachypodietalia pinnati to unite the mesoxeric grasslands. His order comprised the alliances Cirsio-Brachypodion pinnati and Mesobromion erecti. Subsequent large-scale analyses, notably by Willner and colleagues in 2017 and 2019 using extensive datasets from Central and Eastern Europe, confirmed that three main subtypes of the class can be distinguished by soil conditions: mesoxeric, xeric and rocky. The mesoxeric order concept has since been adopted in major syntheses including the EuroVegChecklist of Mucina and colleagues in 2016.

Here the nomenclatural complication deepens. Under the code’s priority rules, Korneck’s name Brachypodietalia pinnati is technically a nomen superfluum, a superfluous name, because his original diagnosis included the type of the earlier-published Brometalia erecti. A superfluous name automatically receives the type of the name it should have replaced, meaning that under strict application of the rules the correct name for the mesoxeric order would be Brometalia erecti W. Koch 1926. But because that name has been applied to at least two vastly different concepts, a geographic order spanning mesoxeric and xeric grasslands, and in some usages a xeric-only order excluding its own type, adopting it for the modern mesoxeric order would sow confusion rather than resolve it. Dengler and colleagues had already chosen the alliance Cirsio-Brachypodion pinnati as the lectotype of Brachypodietalia pinnati in 2003, and numerous authors across Europe have explicitly used the name as a proposed conserved name, but the formal step of submitting a proposal under the code had never been taken until now.

The new proposal therefore asks the Group for Phytosociological Nomenclature to conserve Brachypodietalia pinnati Korneck 1974 against the earlier names Brometalia erecti W. Koch 1926 and Scorzoneretalia villosae Kovačević 1959, and to do so with a conserved type, the alliance Cirsio-Brachypodion pinnati Hadač & Klika in Klika and Hadač 1944. The authors draw an explicit analogy with an earlier successful case, the conservation of the alliance name Mesobromion erecti against the earlier Bromion erecti, argued by Terzi and colleagues in 2016 and ruled on by Theurillat and colleagues in 2017. The Scorzoneretalia villosae, typified by the Scorzonerion villosae, is included among the names to be rejected because it has never been used for a pan-European mesoxeric order, and the current broad order concept comprises five xeric or rocky orders alongside the single mesoxeric one.

Carefully, the authors have framed the proposal so that it constrains only the mesoxeric usage. They deliberately refrain from proposing Brometalia erecti as a nomen ambiguum, keeping that name and others available for researchers who prefer the traditional concept of purely geographically delimited orders. If the proposal is accepted, an order comprising the alliances Bromion erecti and Xerobromion, but not the Cirsio-Brachypodion, would still legitimately be called Brometalia erecti. An order combining the Festucion valesiacae with the Cirsio-Brachypodion, but lacking the Bromion erecti, would bear the name Festucetalia valesiacae, since that name has priority over Brachypodietalia pinnati. And an order containing the Scorzonerion villosae and Saturejion subspicatae without the two core mesoxeric alliances would continue to be called Scorzoneretalia villosae. In other words, the conserved name could only be used when referring to a purely mesoxeric order, while dissenting authors would face no change to their own practice.

The precise boundaries of the mesoxeric order remain an open research question, and the authors are candid about this. A pan-European synthesis based on vegetation plots from the European Vegetation Archive is still pending, so it is not yet fully resolved which alliances belong to the order. The consensus core, according to the EuroVegChecklist, includes the Bromion erecti, Cirsio-Brachypodion pinnati, Filipendulo vulgaris-Helictotrichion pratensis, Gentianello amarellae-Helictotrichion pratensis, Potentillo montanae-Brachypodion pinnati, Polygalo mediterraneae-Bromion erecti and Chrysopogono-Danthonion calycinae. Recent analyses by García-Mijangos and colleagues in 2021 supported adding the Potentillo montanae-Brachypodion pinnati and much of the Iberian Brachypodion phoenicoidis, demonstrating that two Spanish associations previously assigned to other classes and orders in fact belong to the Brachypodietalia pinnati. The position of the French type association of the Brachypodion phoenicoidis, however, remains less clear, and the authors deliberately excluded that order from their proposal until a large-scale plot-based classification can settle the question.

Whether the Group for Phytosociological Nomenclature accepts the proposal will determine the official name attached to some of the most species-rich plant communities on Earth. The authors argue that acceptance would support nomenclatural stability while avoiding the confusion caused by identical names applying to vastly different concepts, and that the time is ripe for a formal decision. For the scientists who survey, map and defend Europe’s semi-dry calcareous grasslands, a settled name would mean that habitat assessments, red-list evaluations and cross-border conservation strategies all rest on a shared, unambiguous vocabulary. In a field where a single name can carry half a century of shifting meanings, the conservation of Brachypodietalia pinnati would be a quiet victory for clarity, achieved not in the field with a quadrat and a species list, but in the pages of a nomenclatural proposal.

Subject of Research: Nomenclatural conservation of the grassland order name Brachypodietalia pinnati within the class Festuco-Brometea

Article Title: Proposal (31) to conserve the name Brachypodietalia pinnati Korneck 1974 as a nomen conservandum with a conserved type

Article References: Dengler, J., & Willner, W. (2023). Proposal (31) to conserve the name Brachypodietalia pinnati Korneck 1974 as a nomen conservandum with a conserved type. Vegetation Classification and Survey, 4, 63-68. https://doi.org/10.3897/vcs.100985

Image Credits: AI Generated

DOI: 10.3897/VCS.100985

Keywords: Brachypodietalia pinnati, Festuco-Brometea, phytosociological nomenclature, nomen conservandum, mesoxeric grasslands, calcareous grassland, Brometalia erecti, vegetation classification, biodiversity, habitat conservation, Cirsio-Brachypodion pinnati, International Code of Phytosociological Nomenclature