Vegetation Classification and Mapping Project Report - USGS

Vegetation Classification and Distribution Mapping Report: Petrified Forest National Park
C.3 Shrubland
C.3.3. Artemisia filifolia Colorado Plateau Shrubland
Base map class
NatureServe common name
NatureServe code
Sandsage.Colorado.Plateau.Shrubland
Sand.Sagebrush.Colorado.Plateau.Shrubland
CEGL002697
Summary:
This sand sagebrush shrubland association is widespread in the Colorado Plateau of Utah, Arizona,
and probably New Mexico. It occurs on sandy, often somewhat disturbed sites on valley floors, stream
terraces, stabilized dunes and sandsheets, benches, floodplains, and alluvial fans. Most sites are level
to gently sloping, with a few on moderate slopes (up to 21%), and may be oriented to any aspect,
although there is a slight tendency toward warmer southerly aspects. Elevations range from 1122 to
1769 m (3680-5803 ft). Sand or bare soil cover most of the unvegetated ground surface, although
biological soil crusts may have up to 40% cover. Soils are sandy and derived from local sandstones,
alluvium, or eolian deposits. Total vegetation cover ranges broadly, from sparsely vegetated disturbed
sites with less than 5% total cover to stable, well-developed communities with more than 50% cover.
Regardless of cover, the vegetation is characterized by an open shrub canopy dominated by Artemisia
filifolia that is usually mixed with other shrubs, especially Atriplex canescens, Ericameria nauseosa, and
Opuntia spp. Less commonly, the shrub layer will include Vanclevea stylosa, Eriogonum leptocladon,
or Sarcobatus vermiculatus. Coleogyne ramosissima, Ephedra viridis, and Ephedra torreyana are generally
absent or have only trace cover. The herbaceous layer is moderate in terms of species composition
and provides sparse to moderate cover. Graminoids that are consistently present include Achnatherum
hymenoides and Bromus tectorum; some sites may also have Hesperostipa comata, Pleuraphis
jamesii, Sporobolus cryptandrus, and Vulpia octoflora. Forbs vary among sites but are typical of sandy
habitats, including Abronia fragrans, Lepidium montanum, Oenothera pallida, Salsola tragus, and
Sphaeralcea parvifolia. Cryptogams may be absent or may provide up to 40% cover.
Classification confidence: 1 - Strong.
Classification comments:
Globally. This association is distinguished from other Artemisia filifolia shrubland associations
by its restriction to the Colorado Plateau, the somewhat mixed shrub canopy that usually
includes Atriplex canescens, a poorly-developed herbaceous layer and often a number of species
that indicate disturbance or somewhat alkaline conditions. This association also occurs
in a broader range of habitats than other Artemisia filifolia types. However, Artemisia filifolia -
Ephedra (torreyana, viridis) Shrubland is poorly defined, and many stands of Artemisia filifolia
Colorado Plateau Shrubland contain one or the other species of Ephedra; it is possible that
these two associations should be combined.
Petrified Forest National Park. Artemisia filifolia Colorado Plateau Shrubland was distinguished
from Artemisia filifolia / Bouteloua eriopoda Shrubland by a higher shrub cover and
a diverse herbaceous layer that is not dominated by either Bouteloua eriopoda or Bouteloua
gracilis.
C20