The Crown of the Continent landscape looks different today than it looked one hundred years ago and is likely to be different decades from now. Plants that grow in a given place tend to be replaced when disturbances like fire, wind, avalanches, and disease alter existing plant communities.
This succession is a natural process with fairly predictable yet complex patterns. As an example, in moist forests sites such as the Trail of Cedars in Glacier National Park, fire most likely spread through the area many years ago. Grasses and shrubs invaded first, followed by lodgepole pine, whose unique adaptations allow it to thrive after fire. Ironically, as the lodgepole matured, they eventually created so much shade that their seedlings failed to survive, and the next stage of succession began. More shade-tolerant trees, such as spruce and fir, took over and became the dominant species. As spruce and fir matured, even greater shade-tolerant species like western hemlock and western red cedar took root and grew.
A new disturbance can set the process back at any time during succession, creating a mosaic of mixed-age ecosystems. Add variables like soil type, moisture, elevation, and climate, and the process becomes even more complex.