On the lower slopes of the Sistema Central extensive extensions of holm oaks survive. At a higher level, between 1000 and 1100 masl, chestnut trees abound. Above them predominates the pyrenean oak, very resistant to the cold, whose stratum extends until the 1700 masl. However, many oak groves have disappeared, cut down by man and replaced by pine trees of repopulation. The main native pine forests are found in the Sierra de Guadarrama. The subalpine zones located between 1700 and 2200 masl are home to thickets of cytisus oromediterraneus and junipers.