Classification Distribution Vegetation Accuracy

The herbaceous-shrub landcover class is a mixture of three already defined landcover classes: willow, dwarf shrub and dry-mesic herbaceous. This combination class was created because of extensive over-classification of the low shrub-sedge class on the upper slopes on the south side of the Alaska Range. The low shrub-sedge class at this slope position was actually a combination of the willow, dwarf shrub and dry-mesic herbaceous classes. We were unable, however, to split the low shrub-sedge class into its proper components of willow, dwarf shrub and dry- mesic herbaceous. The low shrub-sedge class, consequently, was reclassified to a new class, herbaceous-shrub, at or above alder line (generally elevations of 600 m or greater) on the park south side. For a complete description of the methods used to define this class see Stevens et al. (2001). The class is comparable to the Viereck et al. (1992) hierarchical levels closed tall willow (IIB1a), open tall willow (IIB2a), closed low willow (IIC1b), open low scrub (11C2), dwarf scrub (IID), dry graminoid herbaceous (IIIA1), mesic graminoid herbaceous (IIIA2), dry forb herbaceous (IIIB1) and mesic forb herbaceous (IIIB2).

The herbaceous-shrub class is found on mountain ridges and slopes on the south side of the Alaska Range. It occurs both above the alder zone and mixed in with the alder class moving down slope. The willow and dry-mesic herbaceous classes occur adjacent to this class both up and down slope. The dwarf shrub class typically borders the herbaceous-shrub class upslope. The sites are typically moist, and occur below 1,500 meters elevation (Table 3). It is a major component of the Alaska Range-south-central mountains and valleys ecoregion (Tables 4a and 4b; Clark 1998), and covers 1.1% (68,872 acres) of Denali National Park and Preserve (Table 5).

For species and structural information please review the individual landcover classes that make up the herbaceous-shrub class: willow, dwarf shrub and dry-mesic herbaceous. Note that sites dominated by Dryas octopetala are uncommon in the herbaceous-shrub class. Instead, dwarf shrub species are mixed, including Empetrum nigrum and Vaccinium uliginosum, and have a strong graminoid component. The dry-mesic herbaceous component is typically lush and includes Calamagrostis canadensis, Athyrium filix-femina, Epilobium angustifolium, Geranium erianthum, Heracleum lanatum and Sanguisorba stipulata.

The accuracy of the herbaceous-shrub class was not assessed because the class is a combination of other map classes.