Climatic classification and ordination of the Spanish Sistema Central: relationships with potential vegetation

Monthly precipitation and monthly mean temperature records from 255 meteorological stations in Central Spain (Spanish Sistema Central) were analyzed by cluster and principal component analyses. Classification separated 14 groups according to altitude, geographical distribution, as well as the combination of rainfall and temperature. The first cluster emerged as significantly higher and colder than the second. Then, two ordinations were carried out: one for the 14 groups extracted from the classification and a second for the total station pool. The second ordination was compared with potential natural vegetation data taken around each station. The first ordination summarized the principal climatic characteristics of the Spanish Sistema Central: its behaviour is that of a typical Mediterranean mountainous territory combining summer aridity and variation of temperature with altitude and the influence of winter winds. The ordination of all stations reflected a thermal, rainfall and summer aridity gradient. Meteorological stations situated at the highest altitude or with highest precipitation records characterized by scrub communities or pine woods and Quercus pyrenaica forests, appeared well-separated along the first two axes. Only the most thermophilous Q. rotundifolia associations could be clearly separated. The fourth axis was useful in clarifying some vegetation overlap of deciduous and sclerophyllous forests, along an east-west summer aridity gradient.