Alpine Dwarf Scrub Gravelly Frozen Slopes

Description

The reference plant community is ericaceous dwarf scrub (Viereck et al. 1992). There are two plant communities in the reference state related to fire.

Solifluction is a process associated with this state but does not happen to a degree resulting in a mosaic of vegetation. Solifluction is the slow, viscous downslope flow of water-saturated soil (Shoeneberger and Wysocki 2017). This process is most active for this site during spring thaw where the upper band of soil material slips on a seasonally frozen layer. Solifluction is a common process associated with several ecological sites in this area and this site can at times have small solifluction lobes. Since these small solifluction lobes are uncommon and do not result in a vegetation mosaic, no alternative solifluction state was developed for this site (see R231XY113AK for a site that does have this alternate state).

Submodel

Description

Non-sorted circles are a type of patterned ground. On gentle slopes, these patterned features are roughly circular and as steepness increases these features become slightly elongated. In this area, the diameter of non-sorted circles commonly ranged from 1.5 to 10 feet and are mounded above the surrounding vegetation. These circles are considered non-sorted due to an absence of coarse rock fragments on their borders (Schoeneberger and Wysocki 2017). For this site, these non-sorted patterned ground features form through the process of cryoturbation.

Cryoturbation is a collective term used to describe all soil movements due to frost action, characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits (Schoeneberger and Wysocki 2017). In this instance, these patterned ground features result through differential heave of frost susceptible material resulting in mounds (Schoeneberger and Wysocki 2017). During active periods of cryoturbation, freshly churned up mineral soil and rock fragments were commonly observed on mounded surfaces. The formation of these non-sorted circles leads to a distinct mosaic of vegetation.

This vegetation mosaic has two distinct plant communities that are associated with different positions on or adjacent to the non-sorted circle. The first plant community occurs in adjacent areas that have not yet formed these non-sorted circles or is the community that occurs between the non-sorted circles (community 2.1). This community generally resembles the reference state vegetation. The second plant community occurs on the non-sorted circle (community 2.2), which supports a lichen dominant plant community. When compared to community 2.1 soils, the non-sorted circle soils are much drier and have much less organic matter.

Submodel