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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. [ABSTRACT FROM AUTHOR]

Forest decline may be a complex disease caused by the interaction of a number of interchangeable factors (both abiotic and biotic), leading to gradual deterioration of the forest. These factors have been classified as predisposing, inciting or contributing factors. Pinus pinaster Ait. is one of the most important forest species in Spain because of its protective value and the high timber yields obtained. Maritime pine decline has been observed in several forests in the centre of the Iberian Peninsula, manifested as transparency at the crown, small needles, foliage discolouration and premature tree death. The aim of this study was to unravel the role of predisposing, inciting and contributing factors in Mediterranean maritime pine decline in Spain. Various parameters were measured in 27 circular plots of radius 15 m in natural stands of P. pinaster ssp. mesogeensis . The data obtained indicated better forest health status in pure stands, in which thinning has been carried out, than in unthinned mixed stands. High values of total height and spring precipitation showed better forest health, whereas high tree density was associated with the poorest forest health status. The results suggest that predisposing factors such as competition and water deficit have triggered the decline of P. pinaster. [ABSTRACT FROM AUTHOR]