Long, severe winter temperatures 3. Growing season too short to favor deciduous habit among most dominants. Better to retain leaves on trees over winter, rather than waste valuable time and energy during the brief growing season with leaf elongation. Needleleaf form necessary to minimize mechanical damage to leaves during long, cold winter. Small needle surface area and waxy cuticle resists water loss during long winter, minimizes exposure to physiological drought stress.
Conifer form has narrow crown, flexible branches.
Helps to shed excess snow and minimize ice buildup. C. Boreal forests have very low productivity compared with other forests, even when compared with other conifers, such as on the Coastal Plain, or in the Pacific Northwest. If harvested, recover very slowly. D. Northern margin - trees thin out and become stunted. Open woodland grades into tundra.