White spruce (Picea glauca) in this region is preserved as relict trees that are dead but not decayed due to low temperatures. Subfossil trees are preserved in permafrost, glacial sediment deposits and in the White River Ash (pictured above). This last deposition resulted from a major volcanic eruption in the Wrangell Mountains around 800AD. The figure below shows progress to date in finding, sampling, and processing wood material from this region.
An example of an extended Alaska record: The tree-ring chronology below, from northwest Alaska, includes archaeological material (originally collected by Giddings), driftwood and living trees