Shrubs and Dwarf Shrubs
Shrubs are woody plants that are less than 10 m tall when mature, and are usually multi-stemmed. In the boreal forest shrubs are often less than 3 m tall (~10 ft) tall, but some willows can attain tree-like heights of greater than 5 m. Dwarf shrubs are woody plants that are less than 30 cm (~1 ft) tall and characteristic of the alpine tundra blanketing the ridges and slopes of Denali above approximately 3500 feet (1066 m) in elevation.
Shrubs are very abundant in Denali, including many of the areas often frequented by visitors along the park road. Shrubs are absent from only the highest alpine areas and some of the very wettest wetland plant communities. Shrubs tend to occur most abundantly in subalpine regions where trees are less common, in riparian areas along streams, (where many species of willows and alders like to grow). Shrubs are also common in the understory of some of the boreal forest types in the park. There are a few species of shrubs that occur above treeline, even at elevations up to 1500 m (5000 ft).
There is a much higher diversity of shrub species in Denali compared to trees. There are fifty-two species of shrubs representing 10 different plant families that occur in Denali National Park and Preserve, 29 of which are included in the Atlas. The willow (Salicaceae) and heath (Ericaceae) families contribute the most species of shrubs to our flora, with 17 and 11 species respectively. Other plant families that are represented by shrubs in our flora are the Rose (Rosaceae), Birch (Betulaceae), Currant (Grossulariaceae), Honeysuckle (Caprifoliaceae), Dogwood (Cornaceae), Oleaster (Elaeagnaceae), Cypress (Cupressaceae), and Bayberry (Myricaeae) families.
Dwarf shrubs are hardy perennials are the dominant component of many tundra types found in the park, particularly in some areas of late-lying snow in saddles and protected slopes. Mountain Avens (Dryas spp.) tundra is perhaps the most familiar and welcome vegetation type to hikers in the Alaska Range, because it is very common and it usually affords solid footing, dry feet and fast traveling. A surprise for many of our visitors from the south is the dwarf willow shrubs that adorn the mountains of Alaska. These diminutive tundra-dwellers that reach just a few centimeters in height are in fact very close relatives (in the same botanical genus – Salix) of the familiar “weeping willow” tree (Salix babylonica).
There are twenty-six species of dwarf shrubs that occur in Denali National Park and Preserve, twenty of which are included in the Atlas, representing five different flowering plant families:
- Heath family (Ericaceae, 11 species)
- Willow family (Salicaceae, 7 species)
- Rose family (Rosaceae, 5 species)
- Crowberry family (Empetraceae, 1 species)
- Diapensia family (Diapensiaceae, 1 species)