Vegetation Classification and Mapping Project Report - USGS

Appendix C: Global and local plant community descriptions
Ecological systems placement:
Ecological system unique ID
CES304.775
CES304.787
Ecological system name
Inter-Mountain.Basins.Active.and.Stabilized.Dune
Inter-Mountain.Basins.Semi-Desert.Grassland
NatureServe conservation status:
Distribution:
Global rank. GNR (26-Jul-2001).
Globally. The association is found on terraces of large rivers in the Colorado Plateau and
Uinta Basin and likely occurs elsewhere in the southwestern U.S.
Petrified Forest National Park. Sporobolus cryptandrus Great Basin Herbaceous Vegetation
was sampled from just one relevé. It occurred on a sand dune/sandsheet located just east of
the NPS boundary in the central neck of Petrified Forest National Park, south of the railroad
tracks and north of the Puerco River.
Environmental summary:
Globally. This grassland is described from the Uinta Basin and Colorado Plateau where it
occurs on alluvial terraces of large rivers, sandy upper stream terraces along intermittent
washes, and on sand deposits on mesas and plains. Elevation ranges from 1226-1630 m. Sites
are flat to gently sloping valley bottoms, plains or plateaus. Soils are loamy sands and sandy
loams derived from alluvium, eolian deposits, or sandstone residuum. Biological soil crusts are
generally present and may provide up to 30% cover. Stands have generally been disturbed by
flooding, shifting sands, livestock grazing, or human recreation.
Petrified Forest National Park. This association occurred at an elevation of 1630 m (5350 ft)
with no slope.
USFWS wetland system: Not applicable.
Vegetation description:
Globally. This plant association is found on alluvial terraces of large rivers and on sand
deposits on mesas and plains. The sparse to moderately dense (10-30% cover) herbaceous
layer is characterized by the dominance of the warm-season perennial graminoid Sporobolus
cryptandrus. Hesperostipa comata (= Stipa comata), Pleuraphis jamesii, Sporobolus contractus,
Sporobolus giganteus, or Equisetum variegatum may occur in low abundance. Low cover of
native forbs, such as Abronia fragrans, Chamaesyce fendleri, Plantago patagonica, Sphaeralcea
grossulariifolia, Sphaeralcea parvifolia, or the succulent Opuntia polyacantha may be present.
The widespread introduced annual grass Bromus tectorum and several other exotic species
such as Bromus rigidus, Salsola kali, Helianthus annuus, Sisymbrium altissimum, or Tribulus
terrestris may be present to abundant, especially on disturbed riparian stands. An occasional
Brickellia spp. or other shrubs may occur, but they are not dense enough to form a shrub layer.
Moss is important in some stands.
Petrified Forest National Park. Only one relevé was classified as Sporobolus cryptandrus
Great Basin Herbaceous Vegetation, with total vegetation cover of 73% consisting of low
cover of shrubs (3%) and high herbaceous cover (70%). The species diversity was low with
7 species. The vegetation in the herbaceous layer was almost solely dominated by Sporobolus
cryptandrus with 70% cover.
C97