Common tree species include oak , beech, birch, hickory , walnut, maple, elm, and ash in North America, but also has pines and hemlocks. In Europe, fewer species, only oak, ash, and beech, also some pines and larch. Heavily cultivated , most natural vegetation cleared, pines occur as second-growth forests. Species are few, in fact, sometimes consisting of only one or two conifer species. Called the boreal forest , which mainly consists of spruce and fir in North American, and larch in Eurasia.
Some deciduous trees occur, like quaking aspen, willow, and birch, but minor.
The deciduous trees form the pioneering species in land that has been cleared, perhaps due to fire. Associated with Mediterranean climate type, found ringing the Mediterranean Sea in Europe and also on west coast of United States in California . Trees are evergreen with small, hard leathery leaves that resist water loss in the long summer drought. Typical species in Europe include olive trees , Aleppo pine, live oak, and stone pine, while live oak and white oak are the dominant species in California, forming chaparral . In Europe, human activity has destroyed much of the natural vegetation, while in the US housing developments are built here extensively.