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Vegetation Classification and Mapping Project Report - USGS

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<strong>Vegetation</strong> <strong>Classification</strong> <strong>and</strong> Distribution <strong>Mapping</strong> <strong>Report</strong>: Petrified Forest National Park<br />

C.4 Herbaceous<br />

C.4.6. Ericameria nauseosa / Bouteloua gracilis Shrub Herbaceous <strong>Vegetation</strong><br />

Base map class<br />

NatureServe common name<br />

NatureServe code<br />

Rubber.Rabbitbrush./.Blue.Grama.Shrub.Herbaceous.<br />

<strong>Vegetation</strong><br />

Rubber.Rabbitbrush./.Blue.Grama.Shrub.Herbaceous.<br />

<strong>Vegetation</strong><br />

CEGL003495<br />

Summary:<br />

This shrub herbaceous association occurs on valley floors, swales, <strong>and</strong> alluvial flats in the southern<br />

<strong>and</strong> central part of the Colorado Plateau. Its presence generally indicates disturbance, <strong>and</strong> it may<br />

represent degraded forms of other grassl<strong>and</strong>, shrubl<strong>and</strong>, or woodl<strong>and</strong> communities. St<strong>and</strong>s occupy<br />

gentle to moderate slopes (2-13%) between 1635 <strong>and</strong> 2010 m (5360-6600 ft) elevation. Aspect<br />

does not affect the distribution of this association. Litter <strong>and</strong> bare soil cover most of the unvegetated<br />

surface. Parent materials are variable <strong>and</strong> include s<strong>and</strong>stones <strong>and</strong> shale that have eroded <strong>and</strong> been redeposited<br />

as alluvium or windblown sediments (loess). Soils are well-drained <strong>and</strong> fine-s<strong>and</strong>y or silty<br />

in texture. Total vegetation cover ranges from 10 to 65%, roughly equally divided between the shrub<br />

<strong>and</strong> herbaceous layers. The vegetation is characterized by an open short-shrub canopy of Ericameria<br />

nauseosa that ranges in cover from 5 to 25% <strong>and</strong> an understory dominated by Bouteloua gracilis that<br />

ranges in cover from 5 to 35%. Other shrubs may be present with very low cover, including Tetradymia<br />

canescens, Atriplex spp., Gutierrezia sarothrae, <strong>and</strong> Opuntia polyacantha. Associated graminoids<br />

present include the bunch grasses Achnatherum hymenoides, Aristida purpurea, Pascopyrum smithii,<br />

Pleuraphis jamesii, Sporobolus airoides, Sporobolus crypt<strong>and</strong>rus, <strong>and</strong> Muhlenbergia pungens. Only scattered<br />

forbs are present.<br />

<strong>Classification</strong> confidence: 2 - Moderate.<br />

<strong>Classification</strong> comments:<br />

Globally. Former CEGL001738 <strong>and</strong> CEGL001739 were lumped into this new association;<br />

separation of these two types by subspecies of Ericameria nauseosa was not supported by the<br />

data in Francis (1986).<br />

Petrified Forest National Park. This map class was distinguished from Ericameria nauseosa<br />

Desert Wash Shrubl<strong>and</strong> (CEGL002261) by its restriction to upl<strong>and</strong> areas. This association also<br />

tended to have a proportionally higher herbaceous cover, as well as no codominance by other<br />

shrub species.<br />

<strong>Vegetation</strong> hierarchy:<br />

Physiognomic class V Herbaceous.<strong>Vegetation</strong><br />

Physiognomic subclass V.A. Perennial.graminoid.vegetation<br />

Physiognomic group V.A.7. Temperate.or.subpolar.grassl<strong>and</strong>.with.a.sparse.shrub.<br />

layer<br />

Physiognomic subgroup V.A.7.N. Natural/Semi-natural.temperate.or.subpolar.grassl<strong>and</strong>.<br />

with.a.sparse.shrub.layer<br />

Formation name V.A.7.N.j. Short.temperate.or.subpolar.grassl<strong>and</strong>.with.a.sparse.<br />

microphyllous.evergreen.shrub.layer<br />

Alliance name<br />

Ericameria nauseosa.Shrub.Short.Herbaceous.Alliance.<br />

(A.1546),.Rubber.Rabbitbrush.Shrub.Short.Herbaceous.<br />

Alliance<br />

C78

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