Essai de Phytoclimatologie dynamique dans le nord du Portugal, et réflexion sur les climats mediterranéens portugais

Abstract

A STUDY IN DYNAMIC PHYTOCLIMATOLOGY IN THE NORTH OF PORTUGAL AND THE QUESTION OF MEDITERRANEAN CLIMATES IN PORTUGAL - The climate-vegetation relation in the north of Portugal is studied in a new way. The dynamic continuity of the climate is revealed by the existence of botanical "continuums". The vegetation sampling was made along a continous NW-SE line transect, 185 km long, parallel to the strongest pluviometric gradient. Multivariate analysis and some of the applications of the information theory were used in the floristic study. In the climate study the spatial patterns of daily values of precipitation were analysed for a period of three years. This description was also done by means of multivariate analysis, including CCA for the aerological explanation. A "threshold of hydric satisfaction", around 1400mm of mean annual rainfall seems to determine the existence of an Atlantic vegetation, between the Alvão and Falperra mountains and the Ocean. This vegetation is homogeneous because it does not respond to the udometric variations above this level. To the east, the Atlantic vegetation rapidly dissapears. The comparison between daily precipitation regimes in the different stations and the dynamic interpretation of the differences bring some light to the discussion about the climate in the NW of the Iberian Peninsula: is it an Atlantic or a Mediterranean climate? In the maritime coast of Portugal these two influences mingle, as opposed to the sheltered interior provinces.