West Mojave Plan FEIR/S - Desert Managers Group

irds dependent on water. Remnant populations of these animals are still present today, andcomprise many of the rare species in need of conservation. The ancient river and lakes formedsandy beaches and prevailing winds carried the finer particles to the east, forming hummocksand dunes. These blowsand areas now support unique species of insects, plants, and reptiles,including the Mojave fringe-toed lizard, whose entire distribution can be traced to the formerpath of the ancient Mojave River and Amargosa River.On the west, the western Mojave Desert exhibits communities reflecting the increasedaridity on the east side of the Sierra Nevada and Tehachapi mountains, and the northern flank ofthe San Gabriel and San Bernardino mountains. These ranges capture rainfall from stormsoriginating in the Pacific Ocean and falling over the coast and inland valleys and prevent all butthe larger storms from reaching the desert. The western Mojave Desert is not influenced to agreat extent by the summer thundershowers characteristic of the Sonoran Desert and the EastMojave, though infrequent episodic events from summer storms can cause flash flooding, playafilling, and redirection of stream flow on alluvial fans.The mountainous transition zones within the western Mojave Desert extend downhillfrom open forests of blue pine in the north and pinon pine in the south, through a chaparral zone,to a diverse mixed woody scrub vegetation at lower elevations, often characterized by densestands of Joshua trees. Of interest is the presence of many unique plant species in the southernSierra Nevada, and Central Valley elements of the flora and fauna found in the Antelope Valley,Middle Knob, and Kelso Valley along the west-central boundary of the planning area.The north and northeastern bioregions exhibit many elements of the Great Basin biome.Sagebrush scrub and plants associated with both the Owens Valley and Death Valley ecosystemsextend into the planning area to a limited extent.A limited expression of the Colorado Desert flora and fauna also extends into the WestMojave east of Twentynine Palms and south through Joshua Tree National Park and MorongoValley and is prevalent in the proposed Pinto Mountain DWMA. However, the characteristicsmoke trees, ocotillos and barrel cacti associated with the low desert are restricted to smallregions along the West Mojave boundary.Noteworthy landforms within the West Mojave include five major lava flows at Pisgah,Amboy, the Rodman Mountains, Black Mountain and Fossil Falls, the largest and flattest playain the world at Rogers Lake, and sand dunes in several places, including Olancha, along theMojave River, in the Mojave Valley, and at Twentynine Palms. Deposits of limestone andcarbonate rock in the San Bernardino Mountains support several unique species of plants andsome of the largest mines in the country. Alkaline seeps, springs, and meadows associated withthe San Andreas and other earthquake faults are havens for unusual plants and invertebrates,while occasional fresh water springs support a variety of wildlife, including bighorn sheep.Thirty-two distinct plant communities are found within the western Mojave Desert. Byfar the most common communities are creosote bush scrub and saltbush scrub, which occupy75% of the natural lands. Mojave mixed woody scrub accounts for 13% of the native vegetation.The remaining 29 plant communities are found in isolated areas with unique conditions, such asChapter 3 3-66