In general the Rocky Mountain forest has different kinds of trees that are dominant at different elevations.  Here are the trees that comprise the forest zones found in the Rocky Mountains. 

It has taken me years of hiking in the Rockies to realize that the forest has different trees at different elevations.  In the past I just enjoyed walking and admiring the scenery and beautiful Aspen or evergreen trees.  Well, I knew that the forest changed from the foothills up to the alpine areas above treeline, but I didn’t pay enough attention to the details.  Next time you go for a hike pay attention to how the types of trees change at different elevations.

What Factors Affect What Trees Grow Where?

There are a lot of factors that have an affect on what types of trees grow in different areas.  Some general factors are the amount of sunlight, moisture, and soil type.

More specifically, there are a few things that affect or influence what trees grow in the mountains.  These different factors help explain why there are different forest zones in the Rockies.  I am not going to dive into all of them here, but just want to mention a couple important ones.

Elevation Affects The Rocky Mountain Forest

The higher in elevation you go up in the mountains the harsher the climate becomes.  The environment becomes colder and becomes more heavily impacted by the weather.  For every 1,000 feet of elevation you gain there is a temperature decrease of 3.5 degrees F.

This impacts what kinds of trees can survive in those areas and changes the forest.  The reason for this is the different types of trees are better suited for different conditions.  For example, conifers survive better at higher altitudes than broadleaf trees.

As you get higher and higher in elevation the trees begin to grow shorter (stunted) until eventually they simply can’t survive any longer.

Latitude Affects The Rocky Mountain Forest

Latitude impacts the forest in the same way that elevation does.  The further north you travel the climate becomes colder and harsher.  Moving up in latitude (going north in North America) is similar to going up in elevation.

This means that the dominant trees in Southern Colorado at 8,000 feet elevation may be similar to the dominant trees in northern Montana at a much lower elevation because Montana is much further north than Southern Colorado.

Exposure Or Aspect Affects The Rocky Mountain Forest

Exposure or aspect is simply what direction a slope or spot on the mountain is facing.

In the Rockies, areas on south – facing slopes will get much more direct sunlight than north-facing slopes.  This has a very strong influence on what can live there.

If you look at a mountain you can see the impact of exposure by comparing the vegetation of two slopes at the same elevation with different aspects.

General Rocky Mountain Forest Zones

These three factors play a significant role in determining what trees grow where.  The forest of the Rocky Mountains does have general zones where different trees dominate.

These zones will not be at the same elevation in the Southern Rockies as they are in the Northern Rockies of Montana and Canada.  The types of trees in each zone will be the same, but they may occur at different elevations.

Here are the dominant trees that grow in the Rocky Mountain Forest zones from highest to lowest elevation:

Above Tree Line – Nothing

Spruce-Fir – Engelmann’s spruce, subalpine fir, and Colorado blue spruce

Fir-Aspen – Douglas fir, aspen, and lodgepole pine

Pine–Oak – Ponderosa pine, Gambel oak, willow, and maple

Pinyon–Juniper – Pinyon pine, juniper, cottonwood, and box elder

For more information on any of these trees, click here for common trees of the Rocky Mountains.