Rocky Mountain National Park, Colorado

by Edwin C. Alberts

We suppose that all sorts of plants got started on this new land, but only those species which happened to be adapted for the particular conditions of their time would last long enough to become well established and to produce ample seeds for future generations. This selective elimination of plants which were not adjusted to the changing conditions results in the dominance of certain well-adjusted species. In this way, according to scientists, a climax vegetation develops for a particular situation. As long as the climate remains about the same, the climax vegetation remains relatively stable.

Rugged cliffs and mighty peaks are spectacular products of geologic forces.

Although it has been thousands of years since these plant communities first started on the glaciated bedrock, the struggle for dominance among the plants still goes on. Conditions are not yet completely static and probably never will be. The meadows, the forests, and the barrens of today may be quite different in a distant tomorrow.

PLANT COMMUNITIES

Below 9,000 Feet

In the lower slopes of the park, below approximately 9,000 feet altitude, usually described as the Montane zone, the climate is relatively warm and dry. This type of climate has encouraged a fairly consistent pattern of vegetation that may be considered climax. The forests in this zone are open. The trees are likely to be scattered in characteristically parklike stands and are made up mostly of ponderosa pine. On cool north slopes the stands are thicker, with Douglas-fir sprinkled in or even dominant. With the ponderosa pine on drier sites is juniper (commonly called “cedar”), and above 8,000 feet thick stands of lodgepole pine are sometimes admixed. Along the streams are the distinctive and graceful Colorado blue spruce, associated with willows, birch, and alder. Aspen groves and, in lower altitudes, cottonwoods appear here and there. Many types of shrubs, some characteristic of the foothills, grow in the Montane zone.

The most characteristic forest tree of the lower part of this zone is PONDEROSA PINE. It has dull-green needles from 3 to 6 inches long—longer than those of other pines in the park—which are usually in bundles of three. Although the bark on young trees is black, the mature trees have a yellow-brown bark in characteristically rectangular plates. The cones are about 3 inches long, with prickles on the tips of the cone scales. Capable of growing in warm, dry environments, it is an evergreen of south-facing slopes and is widespread as a forest tree in the southwestern United States. On the cooler, north-facing slopes, DOUGLAS-FIR mingles with the ponderosa pine. Douglas-fir is easily identified by its needles, which grow singly along the branch instead of in sheaths. The needles are flat, blunt, and about 1 inch long; and they have a narrow stalk at the base that pulls off with the needle. This distinguishes it from the blue spruce often found in the same vicinity. The bark is smooth and gray on young trees, but rough, brownish, and deeply furrowed on older trees. The cones are about 2 inches long, made up of broad scales each with a projecting 3-pronged bract. Here, Douglas-fir seldom attains the great size for which it is noted in the Pacific Northwest.

Another conifer growing in this zone, usually along streams or in such other wet locations, is BLUE SPRUCE, one of the most admired evergreens of the West. Its needles produce a bloom, or powder, which gives the tree a distinctive bluish or silver aspect, especially noticeable in midsummer. The cones are from 3 to 5 inches long, tan-colored, with many scales, which have narrow tips but no prickles.

In the upper parts of the Montane zone grow dense forests of LODGEPOLE PINE, so named because the Indians used it for tepee (or lodge) poles. It is characterized by tall, slender, straight trunks, with most of the foliage near the top. Its trunk is usually much smaller than the other conifers of the region—seldom exceeding 20 inches. The bark is much thinner than that of the ponderosa pine; gray scales on the bark of young trees become brown with age. The cones are about 2 inches long and are borne in clusters of two or three, tightly attached to the branch. Cones often remain on the tree for years, the seeds retaining their vitality. After a light forest fire, the undamaged cones will open, releasing the seeds. This is nature’s way of reseeding a fire-swept area and explains the extremely dense stands of lodgepole pine which, for example, you will see near Many Parks Curve.