One Hundred Hikes in Yosemite
We have just delved very briefly into the influences regulating the distribution of plants and animals. Of course, not every species is equally affected by these influences. And therefore every plant and animal has its own range, habitat, and niche. The range is the entire area over which an organism may be found. Some species have a very restricted range; others, a very widespread one. The giant sequoia, for example, occurs only in about 75 small groves at mid-elevations in the western Sierra Nevada. An organism's habitat is the kind of place where it lives. The habitat of the sequoia is typically a gently sloping, forested, unglaciated, periodically burned slope that has abundant ground water. An organism's niche is the functional role it plays in its community. For example, the sequoia provides food and shelter for dozens of insects that utilize the tree's needles, branches, bark, and cones, and additional organisms benefit from soil changes created by the sequoia's roots. At the same time, the sequoia receives essential aid from the chickaree, from a long-antennaed beetle, and from fire (Hike 93). Thus the niche is a give-and-take relationship.
The sequoia's range, though not really large, is great compared to that of a few alpine species such as the snow willow. This "shrub"—usually less than an inch high—is found on only a few old, nearly flat surfaces on or close to the Park's northeast boundary. Animals, having the ability to move, generally have greater ranges than plants, though the Mt. Lyell salamander has a spotty, subalpine range about equal in north-south extent to that of the giant sequoia. An isolated population of this animal survives atop Half Dome (Hike 80).
Some plants and animals have tremendous ranges. For example, the squirreltail is a grass that grows in dry, open habitats from the Park's alpine fell-fields down to the Park's lowest elevations. Outside the Park, it descends to sea level, and its range extends from Mexico north to British Columbia and east to Texas and South Dakota. Some other far-ranging plants growing throughout much of Yosemite are bracken fern, pretty face (golden brodiaea), comb draba, Brewer's lupine, wavy-leaved paintbrush, woolly sunflower, and yarrow.
In the animal kingdom, the mule deer (see Hike 8), mountain lion, coyote, badger, long-tailed weasel, California ground squirrel, and deer mouse are mammals that range through much of Yosemite. Many birds seen in Yosemite have migrated, if not from the south, then from the lowlands, and they follow the development of a food supply that occurs higher and higher as the winter snowpack retreats. In most of the Park you can expect to see the American robin, dark-eyed junco, Brewer's blackbird, northern flicker, white-crowned sparrow, chipping sparrow, American dipper (water ouzel), red-tailed hawk, and northern harrier (marsh hawk). Reptiles and amphibians, despite their limited mobility and their disadvantageous cold-blooded circulatory system, do include a few well-adapted species that have broad ranges. Seen from the foothills up into the subalpine zone are the western fence lizard and Pacific treefrog. The western rattlesnake is also widespread up to about 7000 feet, and a few individuals have made it up to the subalpine zone. Thus, some plant and animal species can adapt to environments and competitors better than others. Most of Yosemite's plants and animals have a more restricted distribution, each living in only several of Yosemite's seven plant communities, and some species live in only one community. We'll now look at some species found in the Park's communities.
Details mentioned in this article were accurate at the time of publication