Ecology

SCAR: Communities of Jackson Hole

In Jackson Hole, there are four major natural communities: Sagebrush, Conifer, Aspen, and Riparian (SCAR).

Sagebrush, September 19, 2013

Sagebrush community, September 19, 2013

Sagebrush communities dominate the flats due to their drought tolerance, which is made possible through various adaptations. Species in sagebrush communities include big mountain sage (Artemisia tridentata), antelope bitterbrush (Purshia tridentata) and Oregon grape (Mahonia repens). Sagebrush communities are found at high elevations in arid environments with xeric soils. The sagebrush community habitat is primarily formed by glacial alluvium (sediment deposited by glacial melt) and aeolian loess (wind-deposited soils). Vegetation in sagebrush communities is low to the ground (a meter or less), which is an adaptation for high wind conditions.

Conifer communities are typically found on north-facing hillsides due to seedling intolerance to sun exposure. Ideal habitat for conifer communities is typically formed by glacial moraines and mountain slopes. Lodgepole pine (Pinus contorta), Douglass fir (Pseudotsuga menziessii), Engelmann spruce (Picea engelmannii), and subalpine fir (Abies lasiocarpa) occur in varying densities in different conifer communities according to the stage of succession and elevation. For example, P. contorta rely on fire disturbance for dispersal of seratonous cones, which allows them to be an early successional species that thrives after disturbance, whereas A. lasiocarpa is typically found at higher elevations.

Aspen, September 19, 2013

Aspen community, September 19, 2013

Aspen communities are typically found in depressions, ravines, valley bottoms, or on the lee side of slopes. Glacial moraines and valleys create these environments, and each environment provides sufficient moisture for drought intolerant aspen seedlings by trapping snow, the primary form of moisture in Jackson Hole ecosystems. Aspen (Populus tremuloides) typically occur in clumps due to asexual reproduction, the most common form of reproduction in aspen. Sexual reproduction is crucial for maintenance of genetic diversity in aspen, and fire disturbance provides key opportunities for recruitment of seedlings for this pioneer species. Aspen communities also include wild rose (Rosa woodsii) and fireweed (Chamerion angustifolium), both of which flourish in the filtered light of the aspen canopy.

Riparian community, September 18, 2013

Riparian community, September 18, 2013

Riparian communities are found along creeks and riverbeds and support drought intolerant species including narrow leaf cottonwood (Populus angustifolia), blue spruce (Picea pungens), and various species of willow (Salix sp.). Rivers formed by glacial meltwater and mountain meltwater run-off form the abiotic (non-living) habitat for riparian communities. Beavers (Castor canadensis) are a crucial species responsible for shaping the Riparian zone, and are often referred to as ecosystem engineers. By creating dams and harvesting trees, the beavers adjust stream flow and affect vegetation density and composition.

The acronym SCAR is a useful tool for remembering each community, and it is also helpful because it is organized by water moisture or content, with sagebrush communities having the lowest water content and riparian communities having the highest. Each community provides crucial habitat for the wide variety of organisms that live in Jackson Hole.

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