Bioclimatic analysis of the Quercus pyrenaica forests in Spain

Abstract

A bioclimatic analysis of the Spanish Quercus pyrenaica forests in the Iberian Peninsula was performed in this study. The purpose of this work was to find out the most suitable bioclimatic variables controlling the distribution patterns of Quercus pyrenaica forests in Spain. The study evaluated climatic data from 78 meteorological stations located in territories that could be potentially occupied by Quercus pyrenaica. The climatic information collected was processed with the BIOCLI computer program to diagnose their bioclimatic characteristics. Ten parameters and bioclimatic indices were afterwards analysed using an ordination statistical method (PCA). With this statistical approach, stations with similar bioclimatic features were grouped and subsequently these bioclimatic groups were associated to 14 different vegetation series of Quercus pyrenaica developing in Spain. The statistical analysis revealed the importance of the ombrothermic indices (mainly Summer Ombrothermic Indices) as well as the Compensated Thermicity Index as useful variables for the discrimination among the Spanish Quercus pyrenaica forests. Therefore, Summer Ombrothermic Indices are essential for the establishment of the boundaries between the temperate and mediterranean forests. The temperate forests require values of these indices higher than forests developing in mediterranean bioclimate. On the other hand, it turned out to be a thermic bioclimatic index of remarkable interest to distinguish either mesotemperate from supratemperate forests or mesomediterranean from supramediterranean ones. Finally, the combination of both type of indices allowed us to separate the Lusitan-Extremadurean, Betic and Gaditan-Alagavian forests that displayed summer ombrothermic indices values lower and generally Compensated Thermicity Index values higher than those of the Carpetan-Leonese forests.