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See Sierra Nevada for general information about the mountain range in the United States. The Biology of the Sierra Nevada is diverse and complex: the plants and animals are a significant part of the scenic beauty of the mountain range. The combination of climate, topography, moisture, and soils influence the distribution of biological communities across an elevation gradient from 1,000 feet (300 m) to over 14,000 feet (4,300 m). Biotic zones range from scrub and chaparral communities at lower elevations, to subalpine forests and alpine meadows at the higher elevations *. There are numerous hiking trails in the Sierra Nevada, which provide access for exploring the different vegetation zones. The western and eastern Sierra Nevada have substantially different species of plants and animals, because the east lies in the rain shadow of the crest. The plants and animals in the east are thus adapted to much drier conditions. The altitudes listed for the biotic zones are for the central Sierra Nevada. The climate across the north-south axis of the range varies somewhat: the boundary elevations of the biotic zones move by as much as 1000' from the north end to the south end of the range. Foothill Woodland and Chaparral Zone
Lower Montane Forest
Upper Montane Forest
Subalpine Forest The upper montane forest is replaced by the subalpine forest near 9,000 feet (2750 m), where the climate is cooler with an even shorter growing season due to long, cold, and snowy winters. Accumulations of three to nine feet (1 to 2.5 m) of snow are typical. The Western White Pine, Mountain Hemlock, and Lodgepole Pine are found in this forest with many subalpine meadows that flower from July through August. Many species live in, or are transient in, this zone, including Clark's Nutcracker. This zone can be seen from the Tuolumne Meadows area east to Tioga Pass. Alpine Zone
Eastern biotic zones The four highest eastern biotic zones are the same as the western zones, but at a higher elevation, due to less precipitation: In the Owens Valley, the Foothill Woodland Zone is replaced by a Pinyon-Juniper Woodland Zone, characterized by Single-leaf Pinyon Pines, Sierra Junipers. The underbrush contains Big Sagebrush (Artemisia tridentata) and Black Bush (Coleogyne ramosissima). Jeffrey Pines may occur along streams. Notable animals in this zone include the Pinyon Jay and the Desert Bighorn Sheep. The Pinyon-Juniper Woodland Zone extends down to 5,000 feet (1500 m) elevation. Below 5,000 feet (1500 m), there is not enough precipitation to support trees. The zones below this elevation are the Sagebrush Scrub Zone, Saltbush Scrub Zone, and the Alkali Sink Zone. These zones are distinguished by soil salinity. Exotic Plants in Yosemite National Park Yosemite National Park has documented more than 130 non-native plant species within park boundaries. These non-native plants were introduced into Yosemite following the migration of early European American settlers in the late 1850s. Natural and human-caused disturbances, such as wildland fires and construction activities, have contributed to a rapid increase in the spread of non-native plants. A number of these species aggressively invade and displace the native plant communities, resulting in impacts on the park's resources. Non-native plants can bring about significant changes in park ecosystems by altering the native plant communities and the processes that support them. Some non-native species may cause an increase in the fire frequency of an area or increase the available nitrogen in the soil that may allow more non-native plants to become established. Many non-native species, such as yellow starthistle (Centaurea solstitialis), are able to produce a long tap root that allows them to out-compete the native plants for available water. Bull thistle (Cirsium vulgare), Common Mullein (Verbascum thapsus), and Klamath weed (Hypericum perforatum) have been identified as noxious pests in Yosemite since the 1940s. Additional species that have been recognized more recently as aggressive and requiring control are yellow starthistle, sweet clovers (Melilotus spp.), Himalayan blackberry (Rubus discolor), Cut-leaved blackberry (Rubus laciniatus) and periwinkle (Vinca major). Lodgepole Needle Miner The Lodgepole Needle Miner (Coleotechnites milleri) is an insect, endemic to the upper Tuolumne and Merced River watersheds of Yosemite National Park and one small headwaters drainage of the San Joaquin River (Sierra National Forest). It lives mostly within the needles of Lodgepole Pine for two years, emerging as a little gray moth for a few weeks in July of odd-numbered years. This keeps any predators from becoming effective control agents and allows populations to escalate rapidly. While regular prehistoric outbreaks of Lodgepole Needle Miners have been confirmed through dendrochronology, historic records document outbreaks from 1903 to 1921, 1933 to 1941, and 1947 to 1963. Extensive stands of "Ghost Forest" and jackstrawed trees are still conspicuous throughout Sierra Nevada. Annual monitoring of Lodgepole Needle Miner density began in 1966, and 28 permanent plots are scattered north of the Cathedral Range. The current outbreak began in 1973 and has been sweeping around the south side of the Cathedral Range, arriving at Sunrise High Sierra Camp in 2001. The Ghost Forest which was evident at the crest between Tenaya Lake and Tuolumne Meadows in the late 1970s was noticeably reforested by 2000. Lodgepole Needle Miner defoliation currently extends over approximately 40,000 acres (162 km²), with nearly 10,000 acres (40 km²) of low to high mortality each year. While lightning fires are frequent in lodgepole pine communities, they usually remain small, with estimated fire return intervals at Yosemite National Park that are long (relative to most other forest types). Thus, fire suppression activities are thought to have had relatively little influence upon species composition, structure, fuels, and natural processes in lodgepole forests. Also, in comparison with Rocky Mountains lodgepole pine forests, fire plays a relatively smaller role, and so the needle miner assumes greater importance in lodgepole pine forest population dynamics in the Sierra Nevada. However, Rocky Mountain lodepole forest dynamics are also heavily influenced by insect outbreaks, primarily bark beetles. National Park Service Management Policies direct managers to allow native pests to function unimpeded except where control is desirable for specific cited reasons, including conserving plants in developed areas. Special-Status Species There are at least 1,300 vascular plant species in the Sierra Nevada, along with numerous bryophytes and lichens. There are at least 450 species of vertebrate animals. A total of 135 plant species in the Sierra Nevada have status as Threatened, Endangered, or Sensitive*. Plants that are Federal species of concern (former Category 2 species) under the Federal Endangered Species Act include: Although Category 2 was abolished in 1996, species of concern is an informal term that refers to those species that might be declining or be in need of concentrated conservation actions to prevent decline. Therefore, these six species continue to be evaluated and managed by the National Park Service. Four state-listed rare plant species are considered restricted and limited throughout all or a significant portion of their range, and may represent disjunct populations at the extreme end of their range: Endangered or threatened species of animals that occur in the Sierra Nevada include *: Wetlands
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