[EN] About 200 photographs taken between 1945 and 1950 in the Maresme Mountains (N Barcelona) are interpreted. These photographs, which are part of my PhD, allow us to examine not only the landscape changes, but also the ecosystem dynamics 60 years later. On most years, the clouds covered the Montnegre summit areas (600-750 m a. s. l.) every afternoon, resulting in dropping water from trees that was important to understand floristic diversity. Therefore, more Eurosiberian (or Subatlantic) plants than expected colonized this Mediterranean mountain. On the west side, the top of the Corredor-Montalt Mountain (600 m a. s. l.) only receives raining water and the acid soil on granite rocks evolved very slowly after the glaciation. These conditions resulted in low soil fertility, as indicated by the presence of stunted Pinus sylvestris and many acidophilous plants. We find some ancient and well-preserved soils on the shallow summit of Montnegre, as indicated by Corylus avellana. This is a small tree able to save water and to multiply roots after the abiotic exploitation related with the mobile and stony ground (see the periglaciarism phenomenon). Precisely, Quercus canariensis reached its northern limit on this type of soils. In the past, formations of Alnus glutinosa climbed until 400-500 m a. s. l. thanks to summer water regulation. Nowadays, however, these formations have been disturbed by urbanization. Usually, by the end of summer, torrential storms increased erosion and damaged littoral villages. Aware people preserved forests or dark dense shrubs called “montnegre” (black mountain). When they made charcoal and plantations of Castanea sativa, they were cautious to avoid hazards and conduct sustainable forest works. Finally, the new subspecies Arisarum simorrhinum atratum is also described.

18 pags., 18 figs. - Nº en homenaje a Pedro Montserrat

Peer reviewed