Vegetation Classification and Mapping Project Report - USGS
Vegetation Classification and Mapping Project Report - USGS
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.3 Shrubl<strong>and</strong><br />
C.3.7. Gutierrezia sarothrae - (Opuntia spp.) / Pleuraphis jamesii Dwarf-shrubl<strong>and</strong><br />
Base map class<br />
NatureServe common name<br />
NatureServe code<br />
Snakeweed.–.(Prickly.Pear)./.Galleta.Dwarf-shrubl<strong>and</strong><br />
Snakeweed.-.(Prickly-pear.species)./.James’.Galleta.Dwarfshrubl<strong>and</strong><br />
CEGL002690<br />
Summary:<br />
This dwarf-shrubl<strong>and</strong> was described from Utah <strong>and</strong> northern Arizona where it occurs on level to<br />
gently sloping hillslopes, plateaus <strong>and</strong> bluffs. Aspects are reported from the southeast, south, <strong>and</strong><br />
southwest. Soils are variable, but tend to be fine-textured <strong>and</strong> may occur over gravel <strong>and</strong> cobbles.<br />
Disturbance may be important in maintaining the vegetation community as some st<strong>and</strong>s have been<br />
created by chaining of trees <strong>and</strong> improper grazing by livestock. This broadly defined association<br />
is characterized by an open dwarf-shrub canopy (10-30% cover) that is dominated by Gutierrezia<br />
sarothrae, frequently with Opuntia spp. <strong>and</strong> an herbaceous layer with Pleuraphis jamesii present to<br />
abundant (1-30% cover). Some st<strong>and</strong>s have a diverse woody layer that includes low cover of several<br />
shrub species <strong>and</strong> occasional Pinus edulis or Juniperus osteosperma trees. The herbaceous layer is typically<br />
dominated by graminoids with several species present including Pleuraphis jamesii, Achnatherum<br />
hymenoides, Aristida purpurea, Bouteloua gracilis, Elymus elymoides, Hesperostipa comata, or Pascopyrum<br />
smithii. There is usually only sparse cover of native forbs like Chamaesyce spp. or Sphaeralcea<br />
coccinea. Introduced species such as Bromus tectorum or Salsola kali may dominate the herbaceous<br />
layer of some disturbed st<strong>and</strong>s.<br />
<strong>Classification</strong> confidence: 3 - Weak.<br />
<strong>Classification</strong> comments:<br />
Globally. This broadly defined dwarf-shrubl<strong>and</strong> includes st<strong>and</strong>s that could also be classified<br />
as a dwarf-shrub herbaceous association.<br />
Petrified Forest National Park. Gutierrezia sarothrae tended to be a rather ubiquitous species<br />
that occurred with notable cover in many associations. These two relevés were classified<br />
as this specific association due to their high cover of Gutierrezia sarothrae without any other<br />
dominant or diagnostic shrubs in the shrub layer.<br />
<strong>Vegetation</strong> hierarchy:<br />
Physiognomic class IV Dwarf-shrubl<strong>and</strong><br />
Physiognomic subclass IV.B. Deciduous.dwarf-shrubl<strong>and</strong><br />
Physiognomic group IV.B.2. Cold-deciduous.dwarf-shrubl<strong>and</strong><br />
Physiognomic subgroup IV.B.2.N. Natural/Semi-natural.cold-deciduous.dwarf-shrubl<strong>and</strong><br />
Formation name IV.B.2.N.a. Cespitose.cold-deciduous.dwarf-shrubl<strong>and</strong><br />
Alliance name<br />
Gutierrezia sarothrae.Dwarf-Shrubl<strong>and</strong>.Alliance.(A.2528),.<br />
Snakeweed.Dwarf-shrubl<strong>and</strong>.Alliance<br />
Ecological systems placement:<br />
Ecological system unique ID<br />
CES304.788<br />
Ecological system name<br />
Inter-Mountain.Basins.Semi-Desert.Shrub-Steppe<br />
C32
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