The term ecosystem refers to a collection of organisms interacting with each other and with the surrounding physical environment. Ecosystems are comprised of numerous components, most notably being the kinds and numbers of inhabiting organisms, whose existence may be limited by physical factors such as altitude, soil, climate, topography, history, and moisture.
In the Eastern Sierra, forest ecosystems are defined by the predominate tree species, which are bound by elevation restrictions. Five distinct forest ecosystems may be explored in the Mammoth Lakes region and each contains a diverse assemblage of interacting plants and animals. In increasing altitude, these biotic zones are the pinyon pine/juniper forests, riparian forests, lower montane forests, upper montane forests, and sub-alpine forests.
Ecosystems of the Eastern Sierra are located at much higher altitudes than similar biotic zones of the western slope of the Sierra Nevada Mountains. These legendary mountains act as a water barrier, making the western slope much wetter and allowing similar forest ecosystems to exist at much lower elevations than on the much drier eastern flank.
Lower Montane Forest Ecosystems
The lower montane ecosystem in the Eastern Sierra region occurs between 7,000 ft. to 8.500 ft. in elevation and is marked by the noticeable dominance of large Jeffrey and ponderosa pines. At the lower elevations of this biotic zone, expect to see more of the ponderosa pine with it's jig saw puzzle-like bark. Jeffrey pine, whose bark is less coarse and smells of vanilla, become more abundant as elevation increases. Additional tree species found within the diverse forests of the lower montane ecosystem include white fir, incense cedar, and juniper.
At these elevations, the climate is characterized by cool, wet winters and dry, relatively warm summers. Once the blanketing snows retreat in the early spring, the lower montane zone becomes the seasonal home of large mammals, such as mule deer, black bear, and coyote. Migratory birds often feed within this ecosystem and industrious squirrels are very common at all levels.
The wooded areas within and adjacent to the town of Mammoth Lakes provide excellent examples of lower montane forests. Shady Rest Park, located on the eastern edge of town near the visitor's center, has several hiking trails that wind through majestic stands of pine. To become immersed within giant old growth ponderosa and jeffrey pines in a more secluded setting, take a half-day hike to Sherwin Lake. The trailhead is located just outside of town and for trail conditions and directions, stop at the visitors center on your way into town.
Upper Montane Forest Ecosystems
Upper montane forest ecosystems are characterized by mature stands of red fir, jeffrey pine, western juniper, and most commonly, lodgepole pine. This biotic zone extends from 8,500 ft. to just above 10,000 ft. in elevation in the Eastern Sierra and at these heights, snow often remains well into the months of May and June, making the upper montane forests ideal for late-season (July-August) wildflower blooms.
The easily distinguishable lodgepole pine dominate the upper montane ecosystem. These straight trunk pines have a very scaley, or reptile-like, bark and do not grow as large as their ponderosa or jeffrey pine cousins. Lodgepole pine are important for a variety of wildlife characteristic of this ecosystem, including ground squirrels, long-tailed ferrets, gray owls, and songbirds (throughout the late summer).
The best places to become immersed within the upper montane forests around Mammoth Lakes are near the Mammoth Mountain Main Lodge area and along the many hiking and biking trails of the Lakes Basin at the end of the Lake Mary Road. Look for large stands of flakey-barked lodgepole pine and giant, short needle red firs of the high altitude forests.
Sub-Alpine Forest Ecosystems
The sub-alpine forest ecosystem extends from around 10,000 ft. to up to 11,500 ft. in elevation in the Easter Sierra. These forests commonly contain whitebark pine and lesser amounts of white and lodgepole pines, with foxtail and bristlecone pines prevalent in some areas. The high elevations of the sub-alpine forests subject the ecosystem to severe winds and prolonged winter conditions.
Species making these elevations their home must be equipped to deal with the harsh, cold climate. Many of the trees found within the sub-alpine forest do reach the heights of the lower elevation ecosystems. Animals making the sub-alpine their home include the jackrabbit, marmot, coyote, and Clark's nutcracker (see the blog on the wildlife of mammoth mountain).
Visitors will find themselves in the lower levels of the sub-alpine ecosystem at the top of Minaret Summit, just past the Mammoth Mountain Main Lodge, where the transition from the upper montane forest to the sub-alpine forest occurs. For the adventurous, many of the high altitude trails leaving from the Lakes Basin pass through this incredibly beautiful forest ecosystem.
Riparian Ecosystems
Riparian ecosystems are collections of organisms that are restricted to areas adjacent to wetlands or streams. These organisms are not suited for the prevailing dry, desert climate of the Eastern Sierra and may only be found along the banks of mountain streams or within moist, swampy meadows. The influence of elevation and climate is less noticeable and riparian forests may extend into the upper montane biotic zone.
Common riparian trees include deciduous species of quaking aspen, mountain alder, willow, and cottonwood. Because they are deciduous, the leaves of these trees will change color in the fall, making for a spectacular experience when hiking one of the many stream side trails in the region during the months of September and October.
To experience the oasis-like riparian ecosystem of the Eastern Sierra, take a hike from town. Mammoth Creek, which flows adjacent to a paved bike path along most of it's course, is lined with thick stands of quaking aspen and mountain alder. As the stream leaves town, stands of large cottonwood begin to dominate and provide shade for a teeming population of trout.
Pinyon/Juniper Forest Ecosystems
Below 7,000 ft. in elevation to about 5,000 ft. in elevation, forests of the Eastern Sierra are dominated by pinyon pine and juniper. These short, yet hardy trees are drought tolerant and can handle the limited precipitation and arid conditions common at these elevations. In areas of higher than normal moisture, stands of ponderosa and jeffrey pine flourish and tower above the dominant pinyon pine and juniper forests. The biotic zone is easily identified by the noticeable appearance of sagebrush and mesquite underbrush densely growing between the trees.
The pinyon pine and juniper forest ecosystem of the foothills below Mammoth Lakes is a great place for bird watching. Mountain bluebird, mountain chickadee, a variety of birds-of-prey, and sage grouse are common throughout this biotic zone. Additional wildlife that thrives within this ecosystem includes mule deer, desert jackrabbits, and coyote.
For those with high clearance vehicles, many of the primitive dirt roads that bifurcate from the Benton Crossing Road, located 6 miles southeast of town on 395, wind into this low elevation forest ecosystem. Additional areas to experience the wonder of the pinyon pine/juniper forest ecosystem are near the McGee Creek trailhead and the community of Crowley Lake, both located only a few miles south of Mammoth Lakes on Rt. 395.
Alpine Zone Ecosystems
The high altitude mountaintops of the Eastern Sierra are within the alpine ecosystem and although devoid of forests, this biotic zone is worth a mention. Above 11,500 ft. in elevation, there is an overall absence of trees and the growth of other vegetation is extremely limited. At these heights, harsh winters combined with extremely short summers and intense winds keep the rocky slopes barren of most life. Sparse patches of grass and ground clinging flowers keep herbivore rodents like the American pika and marmot fed and sustained throughout the brief snow free periods.
Several of the hiking trails leaving the Mammoth Lakes basin eventually ascend well above the treeline into the alpine ecosystem. Popular day hikes include Duck Pass and sections of the John Muir Trail. For high altitude multi-day excursions, the Pacific Crest Trail (PCT) from Mammoth Lakes weaves through vast alpine stretches with epic views the entire way. For expansive, picturesque views of the rocky high alpine mountaintops, travel to Minaret Vista to the west of town on State Route 203 or just look up!
