This photo pair was taken from high altitude, looking east across Big Creek in foreground over a ridge towards the Teklanika R. in the background. Although the air is somewhat smoky from large forest fires that occurred in 2005, this large vista allows us to see changes in the distribution and abundance of white spruce trees that have occurred in the 29 years between these images. Specifically, note the increase in spruce density (darker colored vegetation) on the slopes closest to the viewer below the small ridge in the foreground. This is a south-facing area at the current treeline that has seen an expansion of and increase in density of spruce up in elevation towards the ridge. For contrast, note the small open area on the backside of the small ridge with faces north (left edge of the frame) has seen no apparent encroachment by spruce. This is likely because this area is characterized by cooler soil temperatures and decreased solar radiation due to its north aspect. In general, white spruce prefers south slopes with warmer soils.