Vegetation classification and biogeography of European floodplain forests and alder carrs

Abstract

Aim: Formalized classifications synthesizing vegetation data at the continental scale are being attempted only now, although they are of key importance for nature conservation planning. Therefore, we aim to provide a vegetation classification and to describe the main biogeographical patterns of floodplain forests and alder carrs in Europe. Location: Europe.Methods: A database of more than 40 000 vegetation plots of floodplain forests and alder carrs across Europe was compiled. After geographic stratification, 16 392 plots were available for classification, which was performed using the supervised method Cocktail. We also searched for new associations using semi-supervised Kmeans classification. The main biogeographic patterns and climate-related gradients in species composition were determined using detrended correspondence analysis and cluster analysis.Results: Thirty associations of floodplain forests and alder carrs were distinguished, which belong to five alliances. The Alnion incanae includes riparian, seepage and hardwood floodplain forests in the nemoral and hemiboreal zones (dominated by Alnus glutinosa and Fraxinus excelsior) and in the boreal zone (dominated by A. incana). The Osmundo-Alnion represents oceanic vegetation dominated by Alnus glutinosa, Fraxinus angustifolia and F. excelsior distributed mostly on the Iberian Peninsula and composed of species with Atlantic distribution and Iberian endemics. The Populion albae comprises floodplain forests frequently dominated by Fraxinus angustifolia, Populus alba and P. nigra that are widespread in floodplains of large rivers under summer-dry climates in the Mediterranean region. The Platanion orientalis represents eastern Mediterranean floodplain forests dominated by Platanus orientalis. The Alnion glutinosae includes forest swamps dominated by Alnus glutinosa distributed mostly in the nemoral and hemiboreal zones. The main biogeographic patterns within European floodplain forests and alder carrs reflect the climatic contrasts between the Mediterranean, nemoral, boreal and mountain regions. Oceanic floodplain forests differ from those in the rest of Europe. The hydrological regime appears to be the most important factor influencing species composition within regions.Conclusions: This study is the first applying a formalized classification at the association level for a broad vegetation type at the continental scale. The proposed classification provides the scientific basis for the necessary improvement of the habitat classification systems used in European nature conservation.

Forest Vegetation of Hardwood Tree Species along the Mirna River in Istria (Croatia)

“…In addition, continental stands are described in the association Lonicero caprifoliae-Quercetum roboris [45], which is broadly understood and of heterogeneous composition. This was also confirmed by Douda et al [10], when they divided it into associations Fraxino panonnicae-Ulmetum glabrae and Ficario vernae-Ulmetum campestris, within the alliance Alnion incanae. However, the majority of stands of the association Lonicero caprifoliae-Quercetum roboris belong to the snytaxa within the Carpinion alliance: stands with the species of Illyrian floristic geo-element will be classified within the alliance Erythronio-Carpinion, and those in which these species are lacking in the alliance Carpinion betuli.…”

“…In the previous studies, the community Carici remotaeFraxinetum oxycarpae was classified into different alliances: Alno-Ulmion, Alno-Quercion roboris, Alnion incanae, Carici remotae-Fraxinion oxycarpae, Populion albae [5,9,10,18,29,31,37]. Our research shows a high coincidence with the alliance Carici remotae-Fraxinion oxycarpae, as it is defined in the syntaxonomic overview of the vegetation of Italy [9,18].…”

“…Douda et al [10] consider the majority of them to be synonyms for the association Lithospermo purpureocaerulei-Ulmetum minoris, which they included into the middle Mediterranean alliance Populion albae. The studied forests in Istria fit only partially into such a broadly understood association and its affiliation to the alliance Populion albae.…”

“…The results of the research should help to define the forest vegetation of this important forest locality, but also of the northern part of the Mediterranean region. When it comes to these issues, the opinions of phytocoenologists are quite varied, which is also evidenced by the overviews of the forest vegetation of Europe or its specific regions [5,[8][9][10][11][12].…”

Syntaxonomical analysis of the riparian vegetation of thePorsuk River (Eskişehir-Kütahya/Turkey)

“…If Populion albae, following Mucina et al (2016), is to be understood as an alliance of western South European distribution, our Populus alba woods would have to be assigned to its eastern sub-Mediterranean counterpart, Lauro nobilis-Fraxinion angustifoliae, although the differences are inconsistent across the wide range of the two alliances. This is why we follow Douda et al (2016) in their recent revision of European floodplain forests, treating Populion albae in a wide sense comprising poplar and ash (Fraxinus angustifolia s.l.) forests of large river systems throughout the Mediterranean.…”