Environmental Engineering Reference
In-Depth Information
FIGURE 7.6
Mojave Desert on the Arizona-California border. The dominant shrub on the landscape is creosote bush
( L. tridentata ). Small gray shrubs are white bursage ( A. dumosa ), a valued forage plant for the feral burros seen
in the photo.
drained by streams and rivers that ultimately empty to the sea, the Mojave Desert contains
numerous closed-basin playas (or bolsons) with no outlet to the sea. The northeastern part
of the Mojave Desert, however, does drain to the Rio Grande River and, ultimately, to the
Gulf of Mexico.
Creosote bush occurs throughout much of the Chihuahuan Desert, and other species
shared with the Sonoran Desert include mesquite and ocotillo. The northern portions
of the desert are sparsely populated by stress-tolerant perennials such as creosote bush,
mesquite, and yucca, and these species are complemented by a population of ephemerals
that grow following the summer rains. 19, 20 To the east and south, small shrubs such as
tarbush ( Flourensia cernua ), semi-succulent plants including bear grass ( Nolina spp.), sotol
( Dasylirion wheeleri ), agave ( Agave spp.), and yucca become more common and conspicuous.
Some perennial grasses such as burrograss ( Scleropogon brevifolius ) and tobosa ( Hilaria
mutica ) are also found. As one progresses to the southern and eastern reaches of the
Chihuahuan Desert, succulents from genera including Opuntia , Mammillaria , Echinocereus ,
and Echinocactus are increasingly important in the flora.
The Chihuahuan Desert is largely lacking in arboreal species except in wash communities
where acacia ( Acacia spp.), desert willow ( Chilopsis linearis ), mesquite, and other small trees
occur. Overall, the flora of the Chihuahuan Desert is surprisingly rich given the harsh
environment, yet it remains visually monotonous in comparison to the Sonoran Desert
due to the low structural diversity of life forms.
7.3.3 The Mojave Desert
To the northwest of the Sonoran Desert lies the Mojave Desert. Like the Chihuahuan
Desert, the Mojave Desert is visually rather monotonous compared to the Sonoran
Desert (Figure 7.7). It is also, for the most part, an upland desert. The notable exception
is the Death Valley region, which has a low point of −86 m and is the lowest elevation
point in North America. The extreme dryness of Death Valley results largely from its
being in the rain shadow of the Panamint Mountains and Mount Whitney (the highest
peak in the contiguous United States at 14,504 ft), which lie directly to the west. Over the
Search WWH ::




Custom Search