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alder photo pair
Photo Credits: Fred Dean (1976), Carl Roland (2005)
Ecoregion: Alaska Range Mountains
Change Type: Permafrost dynamics
Permafrost dynamicsAnimation is available
This is an interesting photo pair that shows upland scrub tundra on a hillside near Moose Creek in the Kantishna Hills. The dark green polygons are alder (Alnus viridis) thickets that form in areas with wetter soil and a mineral substrate (i.e. small drainage features and concave slump scars where mineral soil was exposed, and snow and water tend to collect). There does not appear to be a great deal of change evident between the two photo dates, with the exception of some expansion of the alder patches. It is likely that the areas adjacent to the alder are underlain by permafrost, and thus possess a thicker organic horizon and colder soils that can exclude alder communities. With increasing thaw of these areas predicted with global climate change, we would expect to see the expansion of larger-statured vegetation such as alder and willow thickets, and possibly the invasion of trees into this and other biogeographically similar areas.