Continuing with the study of ground vegetation in some plots of the Pan-European
Intensive Monitoring Programme of Forest Ecosystems , in this paper we present the results obtained in the 24Ps plot, located in a pine-silver fir forest at 1,300 m.a.s.l. in Biescas (Huesca, Spain).
After the study during a yea r in this 50 x 50 m plot, and in four 10 x 10 m plots selected in the “buffer” area around the main plot, we consider that vegetation, with characteristics from silver fir and humid Scotch pine forest, seems to progress to a silver fir forest. The high floristic richness of 24Ps plot is due to the existence of different zones : with in the forest, which shows oceanic influence; the lowest, flat
part of the plot, including species from mild meadows; and the western slope, more Mediterranean in character, and with species from dry, rocky pastures, from Quercus cerrioides or Q. ilex rotundifolia forests, or typical of clearings.