Conifers – the Cone Bearers – dominate the forests of the North Cascades. They span the elevation ranges from sea level to the alpine zone, sheltering the low valleys and clinging to the thin mineral soils of the high peaks.
The conifers are often referred to as evergreens because of their characteristic needle or scale-like leaves that persist throughout the year. Yet, two species of larch are deciduous – dropping their needle leaves in the fall after turning a beautiful soft shade of gold.
In the North Cascades conifers define the major forest types, but adding to their complexity are many species of deciduous broad-leaved trees. Species of maple, poplar, and alder grow in the natural openings caused by disturbances to the upper canopy. This happens when large trees are blown over by wind or die of disease. Broad-leaved trees also grow along the edges of streams and rivers where there is more available light.
Woody shrubs, both coniferous and deciduous, grow in the understory of these forests providing shelter and food for wildlife. Many birds such as the rufous hummingbird also use shrubs for nesting. Shrubs are also important along stream corridors where their shade helps to keep water temperatures from getting too high for fish, particularly salmon, and other aquatic fauna.
What is the difference between a shrub and a tree?
Generally, trees are over 20 feet tall and have trunks more than 2 inches in diameter at 4.5 feet about the ground. Shrubs are smaller than trees and often have many small, woody, bark covered stems rising from the base.