Floodplain forests of the Iberian Peninsula: Vegetation classification and climatic features

Abstract

Aims To produce a formalized classification of floodplain forests in the Iberian Peninsula and to assess their main bioclimatic gradients. Location Iberian Peninsula. Methods A data set with more than 3000 vegetation plots of floodplain forests was compiled from vegetation‐plot databases, while climatic data were derived from a digital climatic atlas. After filtering of plots according to their area and geographic stratification, 1892 plots were used to build a typology from association to order level using multivariate classification methods (Fuzzy C‐means, agglomerative hierarchical clustering). The phi fidelity index was used to determine the diagnostic species of the syntaxa in the proposed classification. Main climatic gradients were explored using non‐metric multidimensional gradient analysis, and ANOVA was carried out in order to define the bioclimatic features of Iberian floodplain forests. Results A total of 41 floodplain forest associations were distinguished for the Iberian Peninsula, grouped in nine suballiances, four alliances and two orders. Mediterraneity (summer aridity) was the main climatic driver, as it separates the temperate floodplain forests of the order Alno‐Fraxinetalia from the Mediterranean forests of the Populetalia albae. Continentality and precipitation were mainly relevant at alliance level, as they separated both the temperate alliances Alnion and Hyperico‐Alnion, the latter more oceanic, and the Mediterranean alliances Populion and Osmundo‐Alnion, the latter from more rainy areas. Temperature was an important driver at association level, as the associations included in the same suballiance or alliance differed regarding their thermicity index. Conclusions Our study develops the first formalized classification of Iberian floodplain forests and provides their bioclimatic diagnosis. One new alliance, Hyperico‐Alnion, is proposed for floodplain forests of the Cantabrian watershed. Mediterraneity, continentality and precipitation drive floodplain forest diversity at broad scale, while temperature is the main bioclimatic driver at fine scale. The proposed classification provides the scientific basis for the conservation of this habitat type, with high conservation priority, in southern Europe.

Phytosociological framework and conservation value of supratemperate riparian birch forest of the NW Iberian Peninsula.

“…This proposal, which is strongly homogenizing from both biogeographic and phytosociological points of view, is not coherent with the observed multiplicity of riparian forests in the Cantabrian-Atlantic and Orocantabric territories of the Iberian Peninsula (16 associations, Rivas-Martínez et al, 2002;Rivas-Martínez, 2011;Biurrun et al, 2016).…”

“…In a recent review, Biurrun et al (2016) proposed the inclusion of the riparian birch forests from the mountains among Galicia, Castilla & León and N Portugal, from the western Cantabrian Range, and from the Moncayo Massif (Iberian Range) in a single association: Carici reuterianae-Betuletum celtibericae. This proposal, which is strongly homogenizing from both biogeographic and phytosociological points of view, is not coherent with the observed multiplicity of riparian forests in the Cantabrian-Atlantic and Orocantabric territories of the Iberian Peninsula (16 associations, Rivas-Martínez et al, 2002;Rivas-Martínez, 2011;Biurrun et al, 2016).…”

“…We followed Guerra & Cros (2006-2015 for the bryophyte nomenclature. For the syntaxonomical discussion we used the hierarchical scheme and groups of differential species for upper units proposed by Mucina et al (2016) and Biurrun et al (2016), respectively.…”

“…Riparian forests growing in the supratemperate horizon of the mountains in the GalicianDuriensian sector (Figure 1) Table 5 as holotypus ( Figure 5, photos 4a and 4b Biurrun et al (2016) recently published a review of the syntaxonomy of the Iberian riparian forests and proposed a new hierarchical system of units for the Eurosiberian zone of Spain and N Portugal. In this work, information about NW Iberian birch forests published by Izco et al (1986, Luzulo-Betuletum subass.…”

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

“…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].…”