Environmental Engineering Reference
In-Depth Information
FIGURE 7.7
Joshua tree (
Y. b re v ifoli a
) is the signature species of the Mojave Desert. Shrubs in the background are creosote
bush (
L. tridentata
).
western portions of the Mojave region, rainfall occurs primarily during the cool season,
while precipitation becomes bi-seasonal as one moves to the east.
21
Hard freezes may
occur during the winter and temperatures become very high during the typically dry
summers. The Mojave Desert, like the Chihuahuan Desert, is characterized by playas
surrounded by desert mountains. Within this larger pattern, patterns of soil fertility
exist where “fertile islands” form as a result of essential soil nutrients concentrating
under individual perennial shrubs.
22
Creosote bush again is an important species across the desert. Other species that com-
monly occur include white bursage and the Mojave Desert's most distinctive plant, the
Joshua tree (
Yucca brevifolia
; Figure 7.8). Other small stress-tolerant shrubs occur along with
an ephemeral flora, which becomes evident if and when winter rains occur. Neither arbo-
real species nor succulents make up a significant portion of the flora. Limited riparian
habitats support species such as Fremont cottonwood, Goodding willow (black willow),
velvet ash, mesquite, and the exotic salt cedar.
19, 20
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