How the Trees Came to Glacier National Park

HOW THE TREES CAME TO GLACIER NATIONAL PARK

Harold E. Bailey

Glacier National Park is distinct in the type of plant life which it contains. It is the southern limit for many plants of Canada, and the eastern limit of many Pacific Coast forms. It is little wonder that botanists come from all over the world to collect and study plants here. The park is becoming a classic field for botany just as it is already in the geology. The forests of the park are peculiar because of the small number of kinds of trees and shrubs growing in them. There is no native oak, hickory, elm, walnut, chestnut, sycamore, or locust. The species of birch, alder, maple, plum, cherry, and hawthorn, so abundant in the eastern states, are represented here by a few inferior species. If reason for this be asked, the answer can be found only by going back to ages long past.

The organic remains of the trees, preserved as fossils in rock, offer us the first and most important clue in solving the question. The vegetation has changed many times in the course of the earth's history, but scraps of its green mantle are strewn among the rocks as so many natural archives. From these may be reconstructed the ancient history of the forest of Glacier National Park.

In early Cretaceous times, all North America was covered by forest. Later in that same period, an arm of the sea extending from the Gulf to the Arctic cleft the continent in two. During this time, there developed a marked differentiation of the eastern and western flora. Still later came an uplift and glaciation of the region. Lastly there pushed into unoccupied area, the plants from the two principal regions, the southwest and the southeast, which had not been glaciated. From the Pacific Coast came the grand fir, the Douglas fir, the western larch, the white pine, the hemlock, the red cedar, the yew, and the black cottonwood. From the distant Appalachians, came the balsam cottonwood, the aspen, the paper birch, and the hawthorn. The Englemann spruce, alpine fir, ponderosa and lodgepole pines are remnants of an old flora indigenous to the region. Pushed down from the Northland by the great Ice Ages came forms of elfin stature which have since retreated to the cold mountain tops as a warming climate made lower elevations tenable to warmth-loving plants.

As we gaze upon the glory of our forests, we seldom think of their past history or of the reasons why or how its individuals came to be present. This presents a most fascinating aspect which engages the minds of those researchers who yearly make their pilgrimage to such places as this park, where individuals advancing from different forest sectors clash with each other.