Branches close to the ground, shallow roots, thin bark, and abundant lichens on lower branches combine to make black spruce especially vulnerable to death from fire. Cones high in the crown are generally not consumed, and they retain viable seeds after the fire even though the trees are dead. Birch and aspen are also well adapted to recurring fires, both species vigorously reproducing vegetatively following fire. Additionally both species are prolific producers of light seed which can be disseminated long distances by the wind. Aerial view of downtown Fairbanks near crest of flood on Chena River, August 15, 1967.
Arrow indicates direction of flow of river.
Photograph by the Alaska Railroad. The heavy sediment load of the glacier-fed Tanana River supports an aggrading system where silt deposition associated with floods builds terraces of increasing height on the active floodplain. These fluvial processes, including erosion and silt bar formation, shape the surfaces on which ecosystem processes take place. Insect Outbreaks Insect outbreaks are extensive only in more continental regions of southern Alaska, where the climate is relatively warm. Here insects have eliminated spruce forests over broad areas, leading to extensive areas of grasslands.