Classification Distribution Vegetation Accuracy

Tree canopy cover is less than 10% (or absent). Shrub cover is greater than 25%, shrub height is less than 20 centimeters, and rock cover is greater than 25%. The class is comparable to the Viereck et al. (1992) hierarchical level dwarf scrub (IID).

The physical site characteristics of the dwarf shrub-rock landcover class are similar to the dwarf shrub landcover class, however it has a much higher surface rock component. It is a minor class of alpine areas in the Alaska Range and the Kantishna Hills, and is found on unstable to stable surfaces such as gentle to steep mountain slopes, high mountain valley floors, and rounded mountain ridges. In addition, it occurs on sandbars and alluvial fans. The slope ranges up to >50%, and the elevation ranges up to 1,335 meters based on field data (Table 3). The soils are a thin layer of dry to mesic sand, litter or organic matter. Vegetation typically grows on the thin organic mat. This class is common in the Alaska Range-high mountains ecoregion and the Alaska Range-interior mountains and valleys ecoregion (Tables 4a and 4b; Clark 1998). It covers 1.2% (73,894 acres) of Denali National Park and Preserve (Table 5). The dwarf shrub-rock class often grades into the bare ground, sparse vegetation or dwarf shrub landcover classes. On more stable surfaces, it grades into the alder and willow classes.

This class is dominated by dwarf shrubs, primarily Dryas octopetala and D. integrifolia, interspersed with exposed rock. Few additional species are present. Other dwarf shrubs include Salix reticulata, S. arctica, S. phlebophylla, Cassiope tetragona, Vaccinium uliginosum, Arctostaphylos rubra, and A. alpina. Forbs include Epilobium angustifolium, Aster species, Heracleum lanatum, Veratrum viride, Anemone narcissiflora, and Campanula species. Fruticose lichen species are common.

The producer’s accuracy for the dwarf shrub-rock class is 54.9%, with a user’s accuracy of 50.3%. Most of the errors of omission and commission are with the dwarf shrub and sparse vegetation classes. The number of dwarf shrub-rock signatures available for the accuracy assessment is significantly less than preferred.