sub-headings of this section are the names of vegetation classes
corresponding to those of the vegetation
map. These broad classes do not represent homogeneous community types. Each consists of a variety of intergrading communities that
share some dominant species and have similar physiognomies; they tend to be more similar to each other than to
communities represented by other vegetation classes. The map provides a realistic impression of this
continuously varying mosaic. The vegetation map also includes a matrix showing the
distributions and relative abundances of the more common plant
species across the vegetation classes.
communities are characterized by the presence of Utah
juniper which may be the dominant species or a co-dominant
with Wyoming big sagebrush or black sagebrush.
common shrubs include threetip sagebrush, green
rabbitbrush, and shrubby buckwheat (Eriogonum
grasses, including Indian ricegrass, needle-and-thread,
and bluebunch wheatgrass typically are abundant.
Common forbs include arrowleaf balsamroot (Balsamorhiza
sagitata), tapertip hawksbeard, Hood’s phlox, false
yarrow, and ballhead gilia (Ipomopsis
INEEL’s grasslands are quite variable, but they share one
common characteristic: dominance
by perennial grasses. Nearly pure stands of the robust bunchgrass Great
Basin wildrye (Leymus
cinereus) occur in low lying areas between lava ridges where
deep soils accumulate. Scattered
individuals of green or gray rabbitbrush and big sagebrush
typically are present in these stands.
INEEL grasslands are dominated by rhizomatous species such as
thick-spiked wheatgrass, western wheatgrass, creeping wildrye, or
Douglas’ sedge (Carex
douglasii), while in others, the dominants are bunchgrasses
such as Indian
ricegrass, bottlebrush squirreltail,
needle-and-thread grass, Nevada bluegrass, and bluebunch
wheatgrass. Many INEEL
grasslands are a mosaic of the two growth forms;
patches of rhizomatous grasses are interspersed with areas
dominated by bunchgrasses, and shrubs including black sagebrush,
big sagebrush, green rabbitbrush, and prickly phlox are locally
cactus (Opuntia polyacantha)
is abundant in many of these mixed
grassland communities. Common
forbs include Hood’s phlox, globe-mallow, false yarrow, and the
native annuals small-flowered mentzelia (Mentzelia
albicaulis), western tansy-mustard (Descurainia
pinnata), and western stickseed (Lappula
number of alien species are common and sometimes very abundant.
These include Jim Hill mustard (Sisymbrium
altissimum), desert alyssum (Alyssum
desertorum), salsify (Tragopogon
dubius), and cheatgrass (Bromus
communities usually have high species richness.
in the grassland classification are some areas that have been
seeded to the introduced crested wheatgrasses.
In 1958 and 1959, some 2,650 ha (6,400 acres) were plowed
and seeded in an effort to control the spread of halogeton (Halogeton
glomeratus), an aggressive annual weed that was introduced to
North America from Asia. Smaller
areas that have been disturbed during facilities development,
power line installation, or road construction have been seeded
over the intervening years. Crested
wheatgrass establishes well at the INEEL, and the resulting stands
are quite stable, effectively resisting invasion by native species
(Marlette and Anderson 1986).
A large seeding can be distinguished on the Landsat
image at the intersection of US Highways 20 and 26
near the main entrance to the INEEL;
another is on the southern border, south of EBR 1. Large
areas were also seeded on the southern end of Tractor Flat, which
lies on the east side of the INEEL.