sentences:  The silver fir ("Abies alba") is found on the cool, deep-soiled slopes of the flanks of the Pyrenees, from Navarre to Montseny, forming pure fir woods or, more often, mixed forests with beech trees.The most important areas are in Lleida (Lérida), with 170 square kilometres.In altitude, it extends from 700 to 1700 meters, but its main areas are localized in more humid and dark valleys; these forests are dark, with acidic soil, due to the decomposition of the needles of evergreens.