Vegetation Classification and Mapping Project Report - USGS

Vegetation Classification and Distribution Mapping Report: Petrified Forest National Park
C.3 Shrubland
C.3.11. Krascheninnikovia lanata Dwarf-shrubland
Base map class
NatureServe common name
NatureServe code
Krascheninnikovia lanata.Dwarf-shrubland.was.not.mapped.
as.a.separate.map.class.because.it.lacked.a.definable.
photosignature.and.had.only.one.representative.relevé..This.
one.location.was.incorporated.within.the.map.class.Four-wing.
Saltbush./.Galleta.Shrubland..
Winter-fat.Dwarf-shrubland
CEGL001320
Summary:
This association is known from Colorado Plateau west into the Great Basin and northern Mojave
Desert and east into the northern panhandle of Texas and is likely to be more widespread in similar
habitats in the southwestern Great Plains. It is an alkaline dwarf-shrub association that occurs primarily
on sandsheets, slopes, and plains often on eolian deposits near canyon walls and in alkaline flats in
and around playas and along washes. Sites are flat to steep (up to 40% slope) and occur between 800
and 1770 m (2620-5800 ft) elevation. Soils are rapidly drained loamy sands or sandy loams derived
from alluvium from a variety of parent materials and sandstones that have eroded and been redeposited
by wind and water. It occurs on low to high levels of soil salinity and alkalinity. Total vegetation
cover ranges from 5 to 45% and is characterized by the dwarf-shrub Krascheninnikovia lanata
with cover between 5 and 30%. In southern Nevada, scattered Ambrosia dumosa, Atriplex polycarpa,
Larrea tridentata, Lycium andersonii, Sphaeralcea ambigua, and Suaeda moquinii (= Suaeda fruticosa)
may be present. The herbaceous layer is poorly developed but may contain tufts of the grass
Achnatherum hymenoides. Forbs commonly present include Eriogonum spp., Opuntia polyacantha,
Oenothera pallida, Plantago patagonica, and Sphaeralcea parvifolia. Biological soil crusts may provide
up to 45% cover. Introduced annuals Bromus tectorum, Bromus rubens, and Salsola tragus may be
abundant on some sites.
Classification confidence: 3 - Weak.
Classification comments:
Globally. This is a broadly defined association that includes stands from the Colorado Plateau,
Great Basin, and northern Mojave Desert characterized by the dominance of Krascheninnikovia
lanata without a notable herbaceous layer. The herbaceous layer is typically absent
or sparse or dominated by introduced species such as Bromus tectorum or Salsola tragus. This
is a very-small-patch association as presently defined from Lake Meredith National Recreation
Area, Texas. The concept will need further review to determine if it is a viable association
or should be considered as patches within a broader association.
Petrified Forest National Park. Only one relevé was sampled of this association. More
samples are needed to fully characterize this association at the park.
Vegetation hierarchy:
Physiognomic class IV Dwarf-shrubland
Physiognomic subclass IV.A. Evergreen.dwarf-shrubland
Physiognomic group IV.A.2. Extremely.xeromorphic.evergreen.dwarf-shrubland
Physiognomic subgroup IV.A.2.N. Natural/Semi-natural.extremely.xeromorphic.evergreen.
dwarf-shrubland
Formation name IV.A.2.N.a. Extremely.xeromorphic.evergreen.subdesert.dwarfshrubland
Alliance name
Krascheninnikovia lanata.Dwarf-Shrubland.Alliance.
(A.1104),.Winter-fat.Dwarf-shrubland.Alliance
C42