Vegetation Classification and Mapping Project Report - USGS

Vegetation Classification and Distribution Mapping Report: Petrified Forest National Park
Distribution:
Globally. This widespread, open dwarf-shrub type is found in the western Great Plains from
western Kansas and eastern Colorado, to semi-desert mountains (Oscura and San Andres
mountains) in south-central New Mexico and Colorado Plateau (northern Arizona and southern
Utah). This association is likely more widespread since its dominant/diagnostic species are
common in the western U.S.
Petrified Forest National Park. Krascheninnikovia lanata - Bouteloua gracilis Dwarf-shrub
was identified from one relevé at Petrified Forest National Park. This one relevé occurred on a
sand dune/sandsheet and was located in the central neck of the park in the open plains.
Environmental summary:
Globally. This widespread, open dwarf-shrub type is found in the western Great Plains
from eastern Wyoming, western Kansas, Colorado, and New Mexico semi-desert mountains
(Oscura and San Andres mountains in south-central New Mexico) and Colorado Plateau. This
shrub herbaceous association occurs on alluvial flats, plains, mesas, and desert mountains.
Stands occupy flat to gentle slopes between 1630 and 2080 m (5360-6820 ft) elevation. Ground
cover is largely bare soil. In Colorado Plateau stands, there is often significant cover of biotic
crusts (to 30% cover). The sometimes rocky soils are typically shallow, alkaline, calcareous
and loamy or clayey in soil texture and are derived from shale or alluvium (Francis 1986, Lauver
et al. 1999, Muldavin et al. 2000b). In Kansas, stands occur in areas with sparse vegetation
on uplands and flats. Soils are shallow, rocky, and alkaline (Lauver et al. 1999).
Petrified Forest National Park. This association occurred at an elevation of 1717 m (5633 ft).
The slope was minimal (2%).
USFWS wetland system: Not applicable.
Vegetation description:
Globally. The vegetation contains an open shrub and graminoid layer. The dwarf-shrub layer
is about 0.5 m tall, containing annual stems from a woody rootstock, and microphyllous leaves.
The dominant dwarf-shrub is Krascheninnikovia lanata. The sparse to dense herbaceous layer
is dominated by Bouteloua gracilis. Other shrubs may be present with very low cover, including
Artemisia nova, Atriplex spp., Ephedra viridis, Gutierrezia sarothrae, Opuntia imbricata, and
Opuntia polyacantha. Associated graminoids present may include Achnatherum hymenoides,
Aristida purpurea, Elymus elymoides, Hesperostipa comata, Muhlenbergia torreyi, Pascopyrum
smithii, Pleuraphis jamesii, Sporobolus airoides, and Sporobolus cryptandrus (Francis 1986,
Muldavin et al. 2000b). Forb cover is typically low but may be diverse. Common species in
the Colorado Plateau are Chaetopappa ericoides, Cryptantha crassisepala, Gilia leptomeria,
Helianthus petiolaris, Machaeranthera canescens, Mentzelia albicaulis, Plantago patagonica,
Senecio spartioides, and Sphaeralcea coccinea; Glandularia bipinnatifida is the most constant in
mountains of south-central New Mexico. In Kansas, Stanleya pinnata, a subshrubby perennial
from a woody base, can be over 1 m tall and is often present; Echinacea angustifolia and Liatris
punctata often codominate with Bouteloua gracilis in the herbaceous layer. Exotic annual grass
Bromus tectorum is frequently present in disturbed stands.
Petrified Forest National Park. Only one relevé was classified as Krascheninnikovia lanata
- Bouteloua gracilis Dwarf-shrub, with total vegetation cover of 26%. This vegetation cover
consisted of 13% cover in the shrub stratum and 13% cover in the herbaceous stratum. The
species diversity was 23 species. The vegetation in the shrub layer was dominated by Krascheninnikovia
lanata with 5% cover and Gutierrezia sarothrae with 6% cover. The herbaceous
layer was dominated by Bouteloua gracilis with 5% cover.
C40