By Michael Dallin
LIFE ZONES
As the elevation changes, the plants that can survive at that elevation also change. The lowest reaches of the Park (around 8,500ft in elevation) are much dryer than the higher reaches, hence they includes plants adapted to dry conditions. The elevations where particular plants grow can be broken down into areas called Life Zones. There are three major life zones in the Park:
PONDEROSA PINE
Ponderosa Pine (Pinus ponderosa) typically grow on warm, southern-facing slopes. They generally grow in the montane life zone. Ponderosa Pines have huge root systems to find water on the dry slopes. Because of this, Ponderosa Pines are widely spaced.
JUNIPER
The Rocky Mountain Juniper (Juniperus scopulorum) grows in the lower elevations of the Park. The juniper can be easily distinguished from other trees because its leaves are scale-like and forked. Female trees also have bright blue berry-like fruits.
DOUGLAS FIR
Douglas Fir (Pseudotsuga menziesii) prefer the cool, north-facing slopes of the montane zone. Since north-facing slopes face away from the sun, they receive less sunlight. As a result, water does not evaporate as quickly, and the northern-facing slopes are wetter. This wet climate is what the Douglas Fir needs to survive. Douglas Fir forests tend to be more compact than Ponderosa Pine forests. Douglas Fir forests also tend to contain other species of trees.
QUAKING ASPEN
Quaking Aspen (Populus tremuloides) grow throughout the Park. They are very popular in the autumn, when their green leaves turn right gold, yellow and red before they fall off for the winter. When a slight breeze strikes the tree, the leaves tremble and shake, hence the name "quaking". Quaking aspen tend to grow along streams and marshes, but they can be found anywhere in the Park, usually areas disturbed by fire or logging. They reproduce by seed, but mostly by cloning. The massive root systems of an aspen grove occasionally produce a vertical shoot which becomes a new tree, a genetic clone of the trees nearby.
LODGEPOLE PINE
Trees in a Lodgepole Pine (Pinus contorta var. latifolia) forests tend to be even in height, and they grow tall and straight. Native Americans used to use the lodgepole pines for their tepees. Lodgepole pines are adapted to areas hit by fire -- their seedlings thrive in the charred soil. Hence, lodgepole pines are one of the first species to grow in a burned area. In fact, the heat of a fire signals a lodgepole pine cone to release its seeds. Lodgepole pines do not like shade, and they grow very quickly.
ENGELMANN SPRUCE and SUBALPINE FIR
Englemann Spruce (Picea engelmannii) and Subalpine Fir (Abies lasiocarpa) characterize the subalpine life zone. Strong winds blow the snow off of the tundra into the subalpine zone, and therefore the zone is the much wetter than other zones in the Park. Engelmann spruce and subalpine fir are adapted to these conditions. These species are generally the climax of the forest -- that is, they eventually take over areas where lodgepole pine and aspen grow after a burn, forcing these other species out. These forests grow all the way to treeline, where the harsh conditions shape the trees into interesting forms. Krummholz, flag (banner) and layered trees are common forms at treeline.
LIMBER PINE
The twisted Limber Pine (Pinus flexilis) grows high in the Park, in areas too inhospitable for other trees. Limber pines are one of the first species to grow in burn areas out of reach by lodgepole pines and aspen. Limber pine also grow where the soil is poor, or where wind is strong. The branches of the limber pine are flexible, so they bend -- rather than break -- in strong wind. The roots of a limber pine are very long taproots, further enhancing the tree's survivability.
Rocky Mountain National Park