Vegetation Classification and Mapping Project Report - USGS

Vegetation Classification and Distribution Mapping Report: Petrified Forest National Park
Distribution:
Globally. This association is known from Arches, Capitol Reef, and Petrified Forest national
parks but is also likely widespread in the Painted Desert and canyonlands regions of the Colorado
Plateau in eastern Utah and northern Arizona.
Petrified Forest National Park. Zuckia brandegeei Sparse Vegetation was identified from 17
relevés within Petrified Forest National Park and on the Navajo Nation. This common association
occurred mostly on plateaus, with one stand occurring on a bajada and another in
the plains. The relevés in Petrified Forest National Park were located in the northern wilderness
area northwest of Nizhoni Point, southwest of Lacey Point, in the Black Forest, north of
Onyx Bridge and the Black Forest, and southwest of Chinde Mesa. This association was also
identified from the northern half of the project boundary east of Lithodendron Wash and
west of Lacey Point. Several of the stands were located near The Flattops, including east of
The Flattops in the southern wilderness area, in The Flattops north of the main park road,
southwest of The Flattops and south of the main park road, and north of Jim Camp Wash
and west of The Flattops. In the southern half of the project boundary, this association is also
found west of Dry Wash and the main park road, in the Crystal Forest in the southern wilderness
area, west of the main park road in the Jasper Forest, south of the main road and north of
Long Logs, and in the Rainbow Forest west of Giant Logs. The relevé that was sampled on the
Navajo Nation land was located on the northeastern slopes of Chinde Mesa.
Environmental summary:
Globally. This sparsely vegetated association is common on plateaus at Petrified Forest National
Park but occurs elsewhere on plains, alluvial fans, steep colluvial and badlands slopes,
or shale hogbacks in the Colorado Plateau of northern Arizona and eastern Utah. Elevation
ranges from 1341-1890 m (4397-6200 ft). The soil is a rapidly drained clay loam derived from
shales. Parent materials include the Salt Wash Member of the Morrison Formation; Chinle,
Moenkopi and Curtis formations; or mixed colluvium. The unvegetated surface typically has
high cover of shale chips, sandstone rocks, basalt gravel, conglomerate, or petrified wood
forming a desert pavement surface. Exposure of bare soil is low.
Petrified Forest National Park. This association was sampled between the elevations of 1660
and 1790 m (5430-5880 ft). Slope ranged from none to moderately high (0-19%, average 6%).
Most of the stands had surface rocks that included petrified wood and desert pavement; two
had conglomerate and basalt gravel surface rocks.
USFWS wetland system: Not applicable.
Vegetation description:
Globally. This association has a sparse canopy consisting of Zuckia brandegeei with scattered
Artemisia bigelovii, Atriplex confertifolia, Atriplex obovata, Chrysothamnus viscidiflorus,
Coleogyne ramosissima, Ericameria nauseosa, Eriogonum corymbosum, Eriogonum leptocladon,
Ephedra torreyana, Ephedra viridis, Xylorhiza glabriuscula, Gutierrezia microcephala, and
Gutierrezia sarothrae. The herbaceous layer is low in diversity and provides sparse cover. The
bunch grasses Achnatherum hymenoides, Leymus salinus, and Pleuraphis jamesii are present.
Forbs include Arabis holboellii, Cryptantha sp., Cymopterus acaulis, Eriogonum inflatum, Galium
coloradoense, Penstemon barbatus, Platyschkuhria integrifolia, and Xylorhiza venusta. The
exotic annual grass Bromus tectorum may be present in some stands.
Petrified Forest National Park. Seventeen relevés were classified as Zuckia brandegeei Sparse
Vegetation with total vegetation cover ranging from 1 to 6% (average 2%). The vegetation
cover consisted of a shrub stratum with 0.5-4% cover (average 2%) and an herbaceous stratum
with 0.5-3% cover (average 1%). The species diversity ranged from 4 to 23 species (average 11
species). Zuckia brandegeei was commonly the dominant species; however, it could also act as
an indicator species in these sparsely vegetated areas. It ranged in cover from 0 to 3% (average
1%).
C108