Shade-intolerant species of trees are those that
require full sunlight to thrive. They are sometimes called pioneer
species because they are the first to become established on large,
open, disturbed sites. They include poplar, white birch, jack pine,
and spruce. Stands of these trees tend to be even-aged (all the
trees are about the same age), reflecting the fact that all the trees
became established at the same time, usually after a major disturbance
such as fire.
