Diversity and classification of tall humid herb grasslands (Molinio‐Holoschoenion) in Western Mediterranean Europe

Abstract

Questions What is the community diversity of tall, humid herb grasslands in Western Mediterranean Europe? What are the diagnostic species of the Molinio‐Holoschoenion alliance? What underlying ecological patterns influence their diversity? Location Western Mediterranean Europe (France, Portugal and Spain). Methods We compiled a vegetation plot database of Molinio‐Holoschoenion plant communities. The initial data set of 1056 plots was filtered according to physiognomic and floristic criteria, and geographically stratified. We used hierarchical agglomerative classification and semi‐supervised classification techniques based on the k‐means algorithm as a combination of methods to define vegetation types. A DCA analysis was performed to assess the main ecological drivers of diversity in the Molinio‐Holoschoenion community. Results Seventeen vegetation types were defined, which can be classified in the following major vegetation groups: (1) tall humid grasslands on base‐poor and sandy soils; (2) Scirpoides holoschoenus grasslands on base‐rich soils; and (3) eastern Iberian and southwestern French Schoenus nigricans and/or Molinia caerulea grasslands. The water‐logging gradient was recognized as a major underlying pattern influencing the diversity and distribution of Molinio‐Holoschoenion, and at a second level, the soil factor. Conclusions We suggest a revision of the concept of the Molinio‐Holoschoenion alliance to be considered for the interpretation of habitat type 6420 of the European Habitats Directive, which should include Mediterranean wet dune slacks and tall, humid inland grasslands. This vegetation type is largely distributed on the eastern Iberian Peninsula, where base‐rich soils are predominant and Scirpoides holoschoenus grasslands comprise the main floristic composition of the alliance.

The effects of climate change on the flowering phenology of alder trees in southwestern Europe

“…In some waterlimited ecosystems, the effect of aridity has the opposite effect (Osborne et al, 2000). Vegetation in areas with increasingly warmer and drier conditions will suffer changes in competitive interactions because plant species' drought tolerance determines plant survival to intense summer droughts and extreme heat events (García-Madrid et al, 2016;Peñuelas et al, 2001). Furthermore, global warming affects the timing of the main stages of plant life cycles from a phenological perspective (Picornell et al, 2019;Rojo and Pérez-Badia, 2014).…”

Silaum silaus (L.) Schinz and Thell.—Habitat Conditions and Variation in Selected Characteristics of Populations at Different Densities

“…It is sporadically noted on grasslands of the alliance Mesobromion [59], on semi-dry grasslands of the class Festuco-Brometea at the foot of hillsides [60] and even in scrubs and marsh woodland [61]. In Western Europe, Silaum silaus occurs on mesophilic and alluvial meadows of the class Molinio-Arrhenatheretea [7,62] and in tall humid herb grasslands of the class Molinio-Holoschoenion [63]. Meanwhile, in Asia, it is found in halophytic communities of rushes and meadows of the class Asteretea tripolium [39,45,64,65].…”

Grasslands of Navarre (Spain), focusing on the Festuco-Brometea: classification, hierarchical expert system and characterisation

“…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 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).…”