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Douglas Fir in the Desert - A Relict Population

It would likely surprise many visitors to the Island in the Sky district of Canyonlands National Park to learn that the wide-open plateau that they are standing on was once covered in a much denser forest. Prior to about 10,000 years ago, as the Earth was transitioning out of the last glacial period, this region had a significantly cooler and wetter climate. This supported a much different plant community than the high desert ecosystem we experience today. We could imagine that our mesa top was covered with ponderosa pine, white fir, aspen and Douglas fir trees, much like nearby higher elevation areas currently do, such as the La Sal and Abajo mountains. As this region warmed and dried, these forests were replaced by the pinion-juniper woodland, grassland, and sagebrush steppe communities that are better adapted to the conditions we have here now.

So how is it that we a find a lonely copse of stately Douglas fir trees tucked in an alcove visible from Shafer Canyon Overlook? The impressive geology of Canyonlands is part of the story. Erosional forces that carved these canyons left a cooler, shaded, north-facing alcove for these trees to retreat into as the surrounding temperatures rose. This alcove was formed in the Navajo sandstone. This porous rock layer is well known for holding water, which then seeps out from the recess where it meets a less permeable rock layer. These factors combine as a microenvironment distinct from the surrounding landscape and favorable as a tiny forest refuge.

Known as a relict population, these Douglas firs are isolated by at least twenty-five miles from the next nearest population. Relict populations when separated for long periods of time can develop into new sub species due to limited genetic input. They can also be vulnerable to disappearing altogether if they experience a catastrophic event or if conditions change dramatically. The Colorado Plateau is experiencing warmer and dryer conditions associated with global climate change. During 2017 and 2018, the region experienced 16 months of below average precipitation. If these trends continue, we might see our vegetation shift even further and it is likely that these Douglas Firs will no longer be capable of growing in the park. For now though, we can enjoy these representatives of a different ecosystem from a different time.

- Ranger Tim
July 2020

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Transcript

Hello!

Welcome to Canyonlands National Park. I'm Ranger Tim.

All of our National Parks have surprises to offer, and Canyonlands is no exception. I'm standing at Shaffer Canyon Overlook and with a keen eye you can see one of the surprises that this park has to offer amidst all this sandstone and high desert vegetation.

Tucked into that alcove about a mile behind me, is what is known as a relict stand of Douglas fir tees. These trees are a remnant of a much larger forest better represented on the cool slopes of the La Sal Mountains about 20 miles away to the east.

How do these trees survive in such a challenging location? Well, several thousand years ago at the tail end of the last glacial period, this was a much wetter and cooler location. As the climate warmed and dried, that alcove behind me became the last place they could survive in Canyonlands National Park. This north-facing alcove and a substantial spring in the Navajo Sandstone provides a relatively cool and damp micro-environment.

The Colorado Plateau is experiencing accelerated warming and drying associated with global climate change. The climate trend may mean that even this refuge is not enough to sustain these trees but, for now, we can enjoy these ambassadors from a cooler and wetter time.

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Duration:
2 minutes, 17 seconds

Ranger Tim discusses Douglas fir trees within Canyonlands National Park.

Virtual Ranger Activity

All life on Earth is adapted to their environments in order to survive. Sometimes, these adaptations can make a species unable to live in other conditions. Douglas fir trees used to be able to survive in greater numbers on the mesa tops of Canyonlands, but they now struggle in more warm and dry conditions. Let's looks at other plants near you to think about how they may be adapted to your home environment and think about whether they could survive change.

First of all, you should find a plant. Do you have some living in your house? You could also go outside to your closest green space, like your backyard or a park. You could even look up a plant online! Just make sure you can get a good look at the plant. What are its key characteristics? How would you describe the pieces of the plant? Click on each piece of the menu below while looking at those parts of the plant to try to figure out why the plant you are looking at is the way that it is!
What are the size and shape of your plant's leaves? Are they big and broad or smaller? Bigger leaves can collect more sunlight for plant growth, but they also use more water. Many plants that grow in the dry desert have small leave to conserve water while plants with more water can afford bigger leaves. Do you know if the plant you are looking at has leave all year or does it lose its leaves? Bigger leaves can be easier to damage so often big leaves are only temporary in colder environments. What do you think this means for the growth of the plant when it doesn't have leaves? What do you think this means for the growth of plants with smaller leaves?
How big is your plant? Bigger plants need more energy, minerals and water to survive so the size of the plant can tell you a lot about the plant has to live off of. It the desert, many plants are fairly small because the conditions are harsh. Size can also be a special adaptation to provide different opportunities though. Small plants are less effected by wind while tall plants my be able to avoid being eaten by animals. Why do you think the plant you're seeing is the size it is?
What is the body of your plant like? Is it hard or brittle? Is it smooth or bendy? Plants don't get to move like animals do, so they have to withstand the conditions they grow in. Many desert plants are very hard and resistant to being moved at all. Some of the smaller flowering plants and grasses can be very delicate though, why do you think that is?
Roots anchor plants to the ground, absorbing nutrients and water from the soil. Can you see any of the roots of your plant? While roots are often completely underground, a plant that needs a lot of support or more minerals could have very extensive root systems that you could see stretching out from the plant.
Does your plant have anything that really stands out to you? Does it have a smell? Is it a different color? Does it have flowers or fruits? Each of these things probably helps the plant survive in different ways from other plants. What about your plant seems special and why do you think it is how it is?

Last updated: July 18, 2020