Forest migration northward. Though "Fagus" and "Picea" populations did not expand directionally, they have grown in the Scandinavian range. The movement of "Picea" species in the past 1000 years has shown a strong connection to climate change through a model comparison. In the more recent past, there has been documentation of elevation shifts in distribution of many core forest tree species of Catalonia. The populations of two tree species (European Beech, "Fagus sylvatica"; and Holm Oak, "Quercus ilex") were evaluated in their dynamics over elevations through time. Generally, Holm Oak reside lower on mountain slopes than does European Beech. In the past
Fagus sylvatica in the buds. In autumn, the tree builds the reserves that will sustain it into spring. Given good conditions, a bud can produce a shoot with up to ten or more leaves. The terminal bud emits a hormonal substance in the spring that halts the development of additional buds. This tendency, though very strong at the beginning of their existence, becomes weaker in older trees. It is only after the budding that root growth of the year begins. The first roots to appear are very thin (with a diameter of less than 0.5 mm). Later, after a wave of above