The Alaska Vegetation Classification - Alaska Geobotany Center ...

AFigure 23-A. Aerial view of closed broadleaf forestin interior Alaska. E. Ground view of dosed broadleafpaper birch forest similar to that shown in kI.B. 1. Closed Broadleaf ForestClosed broadleaf forest communities have from 60 to 100 percent tree canopycoverage. Less than 25 percent of the total tree coverage is contributed byneedleleaf (coniferous) tree species (fig. 23, A and B).I.B. 1.a. Closed Red Alder ForestDescription-These communities are dominated by red alder (Alnus rubra) and havea total tree cover of 60 percent or more (fig. 24). Red alder reaches heights of 6 to12 meters (20 to 40 ft) and diameters of IO to 40 centimeters (4 to 16 in). This typehas been described only from the Stikine area in southeastem Alaska, and substantialvariations from the description are to be expected. Woody plants other thanalder are scarce. Common species in the understory include Carex macrochaefa,Calamagrostis nufkagnsis, and in wet areas, Carex lyngbyaei and Potentilla palustris.Distribution and slte characterlstlcs-Red alder forests are common on wet, welldrainedsites with rich, stony, moist soils along creek bottoms and on river terraces insoutheastern Alaska. They also occupy old clearcuts and other disturbed areas onmoist, well-drained sites. Red alder, often with green alder, also forms dense thicketson avalanche slopes.Successlonal status-Red alder communities can be part of a hydrosere betweenmarsh and Sitka spruce-western hemlock forest. Stands on flood plains and riverterraces may remain stable for long periods. Red alder also is successional ondisturbed sites, establishes itself in pure stands on skid trails after clearcut loggingand dominates these areas for several decades.84