Timberline is defined as an imaginary boundary above which trees will not grow. The exact elevation is determined by climate, slope aspect and the species of tree, and varies from 11,000 to 12,000 feet in Colorado. The trees near the absolute boundary are very short, and are usually twisted and scarred by the harsh winds.
The High Alpine Zone
Timberline is a tough place to live, but it is very picturesque, and can be a great place to hike on a warm day. There are many unique plants, and the hiker experiences a very stimulating landscape.
Bristlecone Pines thrive on exposed rocky slopes at elevations of 9,200 to 11,800 feet. They can be found in the southern Rocky Mountains of Colorado, and are usually very small, as well as twisted and picturesque. A Bristlecone specimen has been dated at an age of 4,900 years, which is currently the oldest living species of plant.
The Limber Pine is also very picturesque, and is prevalent near the timberline throughout the Colorado Rockies.
Lodepole Pine, Subalpine Fir, Quaking Aspen and both Engelman and Blue Spruce can also survive at timberline.
A warming climate will gradually move timberline upward.