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Main article: Ecology of the Rocky Mountains
Clickable examples of ecosystem elements
According to the A. W. Kuchler U.S. Potential natural vegetation Types, Rocky Mountain National Park encompasses three classifications; an Alpine tundra & Barren (52) vegetation type with an Alpine tundra (11) vegetation form, a Western Spruce/Fir (15) vegetation type with a Rocky Mountain Conifer Forest (3) vegetation form, and a Pine/Douglas fir (18) vegetation type with a Rocky Mountain Conifer Forest (3) vegetation form.
Colorado has one of the most diverse plant and animal environments of the United States, partially due to the dramatic temperature differences arising from varying elevation levels and topography. In dry climates, the average temperature drops 5.4 degrees Fahrenheit with every 1,000 foot increase in elevation (9.8 degrees Celsius per 1,000 meters). Most of Colorado is semi-arid with the mountains receiving the greatest amount of precipitation in the state.
The Continental Divide runs north to south through the park, creating a climatic division. Ancient glaciers carved the topography into a range of ecological zones. The east side of the Divide tends to be drier with heavily glaciated peaks and cirques. The west side of the park is wetter with more lush, deep forests.
There are four ecosystems, or zones, in Rocky Mountain National Park: montane, subalpine, alpine tundra, and riparian. The riparian zone occurs throughout all of the three other zones. Each individual ecosystem is composed of organisms interacting with one other and with their surrounding environment. Living organisms (biotic), along with the dead organic matter they produce, and the abiotic (non-living) environment that impacts those living organisms (water, weather, rocks, and landscape) are all members of an ecosystem.
The park was designated a World Biosphere Reserve by the United Nations in 1976 to protect its natural resources. The park's biodiversity includes afforestation and reforestation, ecology, inland bodies of water, and mammals, while its ecosystems are managed for nature conservation, environmental education and public recreation purposes. The areas of research and monitoring include ungulate ecology and management, high-altitude revegetation, global change, acid precipitation effects, and aquatic ecology and management.
Despite the importance of preserving the park's natural environment, the area suffers air pollution impacts from Front Range activities, even as the impacts of Denver's infamous brown cloud have been reduced.
Montane zone[edit]
View from the Fall River Road illustrating the montane ecosystem with forested slopes and grassland in between
The montane ecosystem is at the lowest elevations in the park, between 5,600 to 9,500 feet (1,700 to 2,900 m), where the slopes and large meadow valleys support the widest range of plant and animal life, including montane forests, grasslands, and shrublands. The area has meandering rivers and during the summer, wildflowers grow in the open meadows. Ponderosa pine trees, grass, shrubs and herbs live on dry, south-facing slopes. North-facing slopes retain moisture better than those that face south. The soil better supports dense populations of trees, like Douglas fir, lodgepole pine, and ponderosa pine. There are also occasional Engelmann spruce and blue spruce trees. Quaking aspens thrive in high-moisture montane soils. Other water-loving small trees like willows, grey alder, and water birch may be found along streams or lakeshores. Water-logged soil in flat montane valleys may be unable to support growth of evergreen forests. The following areas are part of the montane ecosystem: Moraine Park, Horseshoe Park, Kawuneeche Valley, and Upper Beaver Meadows.
Some of the mammals that inhabit the montane ecosystem include snowshoe hares, coyotes, cougars, beavers, mule deer, moose, bighorn sheep, black bears, and Rocky Mountain elk. During the fall, visitors often flock to the park to witness the elk rut.
Subalpine zone[edit]
Main article: Rocky Mountains subalpine zone
From 9,000 ft (2,700 m) to 11,000 ft (3,400 m), the montane forests give way to subalpine forests. Forests of fir and Engelmann spruce cover the mountainsides in subalpine areas. Trees grow straight and tall in the lower subalpine forests, but become shorter and more deformed the nearer they are to the tree line. At the tree line, seedlings may germinate on the lee side of rocks and grow only as high as the rock provides wind protection, with any further growth being more horizontal than vertical. The low growth of dense trees is called krummholz, which may become well-established and live for several hundred to a thousand years old.
Odessa Lake in the subalpine ecosystem
In the subalpine zone, lodgepole pines and huckleberry have established themselves in previous burn areas. Crystal clear lakes and fields of wildflowers are hidden among the trees. Mammals of the subalpine zone include bobcats, cougars, coyotes, elk, mule deer, chipmunks, shrews, porcupines and yellow-bellied marmots. Black bears are attracted by the berries and seeds of subalpine forests. Clark's nutcracker, Steller's jay, mountain chickadee and yellow-rumped warbler are some of the many birds found in the subalpine zone. Sprague Lake and Odessa Lake are two of the park's subalpine lakes.
Alpine tundra[edit]
Above tree line, at approximately 11,000 ft (3,400 m), trees disappear and the vast alpine tundra takes over. Over one third of the park resides above the tree line, an area which limits plant growth due to the cold climate and strong winds. The few plants that can survive under such extreme conditions are mostly perennials. Many alpine plants are dwarfed at high elevations, though their occasional blossoms may be full-sized.
View on Tundra Communities Trail
Cushion plants have long taproots that extend deep into the rocky soil. Their diminutive size, like clumps of moss, limits the effect of harsh winds. Many flowering plants of the tundra have dense hairs on stems and leaves to provide wind protection or red-colored pigments capable of converting the sun's light rays into heat. Some plants take two or more years to form flower buds, which survive the winter below the surface and then open and produce fruit with seeds in the few weeks of summer. Grasses and sedges are common where tundra soil is well-developed.
Non-flowering lichens cling to rocks and soil. Their enclosed algal cells can photosynthesize at any temperature above 32 degrees Fahrenheit (0 °C), and the outer fungal layers can absorb more than their own weight in water. Adaptations for survival amidst drying winds and cold temperatures may make tundra vegetation seem very hardy, but in some respects it remains very fragile. Footsteps can destroy tundra plants and it may take hundreds of years to recover. Mammals that live on the alpine tundra, or visit during the summer season, include bighorn sheep, elk, badgers, pikas, yellow-bellied marmots, and snowshoe hares. Birds include prairie falcons, white-tailed ptarmigans, and common ravens. Flowering plants include mertensia, sky pilot, alpine sunflowers, alpine dwarf columbine, and alpine forget-me-not. Grasses include kobresia, spike trisetum, spreading wheatgrass, and tufted hairgrass.
Riparian zone[edit]
Mountain stream along Fall River Road is an example of a riparian ecosystem.
The riparian ecosystem runs through the montane, subalpine, and alpine tundra zones and creates a foundation for life, especially for species that thrive next to streams, rivers, and lakes. The headwaters of the Colorado River, which provides water to many of the southwestern states, are located on the west side of the park. The Fall River, Cache la Poudre River and Big Thompson Rivers are located on the east side of the park. Just like the other ecosystems in the park, the riparian zone is affected by the climatic variables of temperature, precipitation, and elevation. Generally, riparian zones in valleys will have cooler temperatures than communities located on slopes and ridge tops. Depending on elevation, a riparian zone may have more or less precipitation than other riparian zones in the park, with the difference creating a shift in the types of plants and animals found in a specific zone.
Wildlife[edit]
See also: Mammals of Rocky Mountain National Park
Rocky Mountain National Park is home to many species of animals, including nearly seventy mammals and almost three hundred species of birds. This diversity is due to the park's varying topography, which creates a variety of habitats. However, some species have been extirpated from the park, including gray wolf, wolverine, grizzly bear, and American bison. Moose are commonly seen in the park, but they were not historically recorded as being part of this particular area of the Rocky Mountains.
Elk[edit]
The park is home to some 2,000 to 3,000 elk in summer, and between 800 and 1,000 elk spend the winter within its boundaries. Because of lack of predators such as wolves, the National Park Service culls around 50 elk each winter. Overgrazing by elk has become a major problem in the park's riparian areas, so much so that the NPS fences them out of many critical wetland habitats to let willows and aspens grow. The program seems to be working, as the deciduous wetland plants thrive within the fencing. Many people think the elk herd is too large, but are reluctant to reintroduce predators because of its proximity to large human populations and ranches.
Other ungulates[edit]
Mule deer investigating some pinecones.
Many other ungulates reside in the park, including bighorn sheep, moose, and mule deer. Bison were eliminated from the park in the 1800s, as were pronghorn and moose, the latter of which was restored to the area in 1978. Moose are now frequently seen in the park, especially on the park's west side. The park's bighorn sheep population has recovered and is estimated at 350 animals.
Predators[edit]
The park is home to many predatory animals, including Canada lynx, foxes, bobcat, cougar, black bear, and coyotes. Wolves and grizzly bears were extirpated in the early 1900s. Most of these predators kill smaller animals, but mountain lions and coyotes kill deer and occasionally elk. Bears also eat larger prey. Moose have no predators in the park. Black bears are relatively uncommon in the park, numbering only 24–35 animals. They also have fewer cubs and the bears seem skinnier than they do in most areas. Canadian lynx are quite rare within the park, and they have probably spread north from the San Juan Mountains, where they were reintroduced in 1999. Cougars feed mainly on mule deer in the park, and live 10–13 years. Cougar territories can be as large as 500 square miles (1,300 km2). Coyotes hunt both alone and in pairs, but occasionally hunt in packs. They mainly feed on rodents but occasionally bring down larger animals, including deer, and especially fawns and elk calves. Scat studies in Moraine Park showed that their primary foods were deer and rodents. They form strong family bonds and are very vocal.
