This is a blog about the native conifers of the Pacific Northwest. It is a companion to the Northwest Conifers site. The blog will focus on timely and interesting details about our conifers, their connections to the rest of the environment, and our connection to them.

Thursday, February 17, 2022

The Great Douglas Fir Migration

Thousands of years ago, people from Siberia migrated across the Bering Land Bridge, which connected Asia to North America. We don’t know if they were explorers looking for new land and opportunities, or if they were driven by famine or drought. They could have been escaping religious persecution like some of the Europeans who came to North America thousands of years later. In any case, it was an adventure, and the adventurers spread across all of North America and into South America.

Millions of years earlier, another migration crossed the Bering Land Bridge in the opposite direction. However, it wasn’t a migration of people. It was a migration of Douglas fir trees. The story of this migration starts in Mexico. The first Douglas fir originated in northern Mexico some 50 million years ago. Douglas fir is closely related to the larch, which evolved from the pines. Douglas fir either branched from the same pine ancestors or from the larch. In either case, the two took quite different forms, the larch becoming deciduous with bundles of needles, and Douglas fir growing evergreen needles that resemble those of the spruce and fir. 

Bigcone Douglas fir
After its departure from the larch, Douglas fir began a long journey north, with some of them branching off to southern California to enjoy a warmer climate. They became a separate species we now know as bigcone Douglas fir (scientific name: Pseudotsuga macrocarpa). As both the scientific name and the common name imply, they have larger cones than the Douglas fir of the Pacific Northwest, although the trees are much smaller. Meanwhile, the trees that continued their migration north became what we know as Douglas fir (Pseudotsuga menziesii). 

Now we must stop and face this question: How can trees migrate? Unlike the strange, magical trees that destroyed the Orcs in “Lord of the Rings,” trees in our world remain rooted in one spot their entire lives. Yes, but their winged seeds can travel! They are adapted to do just that. Let’s suppose that in 100 years a tree grows to be 100 feet tall and produces seeds that are blown a conservative 200 feet from the tree. Thus, the forest would move 200 feet in 100 years, or on average, 2 feet per year. At that rate, it would take about 2500 years for the trees to migrate one mile. It may seem impossible for this forest to migrate all the way to Oregon, until you consider that it had millions of years to complete the trip. At this rate of one mile every 2500 years, the offspring of these seemingly immovable trees could be growing in Portland in less than 3 million years. Not content to linger in Portland, they continued right up the Pacific Coast to Alaska and across the Bering Land Bridge and south into Asia

Before they migrated very far, they faced another difficulty that might have stopped them before they even made it to Portland. The problem is this: As they migrated farther north, the climate changed. With these changes in the climate, the trees must adapt to the new environment. Douglas fir adapted to many changing conditions in their journey north to Alaska and then south into Asia. The journey was not without its setbacks. For example, they encountered a changing climate and several ice ages. And they required the right conditions for their seeds to germinate and survive. Douglas fir seeds germinate best in a seed bed of bare soil. Finally, they may have been stopped by open ocean at the Bering Strait, but at least once the Bering Land Bridge formed and allowed them to cross into Asia. 

Douglas fir seeds with wings

As they moved south through eastern Asia, they adapted to the conditions in different locations, and developed into several new species, including one in Japan, one in Taiwan, and several in China:

  • Japanese Douglas fir (Pseudotsuga japonica), is limited to Japan. Like all of the Asian species of the genus, it is smaller than the Douglas fir of the Pacific Northwest, growing to 100 feet. The cones are also smaller, only 2 in. or less. This species grows only rarely on steep slopes up to 3600 feet elevation.
  • Formosan Douglas-fir, (Pseudotsuga wilsonia), grows mostly in Taiwan with a few locations in China. It is closely related to the Chinese species.
  • Several species of Douglas fir grow in China. Like the Japanese Douglas fir and Formosan Douglas fir, these species are smaller than those of North America and have smaller cones.

Many other conifers have taken similar migrations from North America to Asia across the Bering Land Bridge including some of the true firs (Abies genus), spruce, and pines. And remember the ancient relatives of the Douglas fir, the larch? I suspect the larches took a similar journey, not only migrating to Asia, but to Europe as well. Here in North America, it appears that while migrating north, they also made a right turn and migrated to the East Coast and all across Canada. Some remained in central Alaska.

More recently and closer to home, Douglas fir has been adapting to different conditions here in western North America. Most notably, they have migrated north and south as well as up slope and down slope, with changes to the climate. Cold weather and glacial ice forced them south many times in the past thousands of years. When it warmed and the ice melted, they were able to migrate north again. Note that the glacial till left by the retreating glaciers was the ideal seed bed for the germination of Douglas fir seeds. 

The Cascade Mountains have imposed an interesting split in the population of Douglas fir in the Pacific Northwest. As the saying goes in biology, “Absence makes the genes wander.”  Whenever the members of a species are separated by a barrier, they will develop genetic differences. And if the environment is different in the separate populations, we will be able to see these differences as they adapt to the different conditions. 

As everyone from Oregon and Washington knows, the climate west of the Cascades is mild and damp, well in truth, wet. On the other hand, east of the Cascades, it is dry and prone to temperature extremes and drought. As the separate populations of Douglas fir adapted to these different environments, they evolved into two distinct varieties, and we can now see the differences between them:

Coastal Douglas fir (Pseudotsuga menziesii var. menziesii) now grows in western Oregon and Washington from sea level up to 5000 feet. It also grows along the coast of British Columbia and in the coastal mountains and Sierras of California. This variety grows faster and taller but is less drought tolerant. The needles are green, and the bracts on the cones lie flat on the scales.

Rocky Mountain Douglas fir (Pseudotsuga menziesii var. glauca) grows between 2000 and 7000 feet from central Oregon to the northeast corners of Oregon and Washington, and up into Canada. It also grows throughout the Rocky Mountains up to elevations of 9700 feet, and up to 10,700 feet in Arizona and Mexico. The needles of this variety tend to be blue or gray compared to the coastal form. The bracts on the cones tend to protrude outward from the cones.

As the climate warms, we can expect Douglas fir to change as they try to adapt to new conditions. Or they may attempt to migrate to cooler locations, higher or northward. The problem they face is that the climate is changing quickly. Can the trees keep up? Trees do not adapt or move quickly. Some foresters and volunteers have tried to assist by planting seedlings in new locations where they can grow successfully. This may have some effect, but ultimately, we must stop doing the things that are causing climate change. Can we do that?


More  Info

Douglas-fir: The Genus Pseudotsuga, Denis P. Lavender and Richard K. Hermann. You can download the PDF here.

Intercontinental disjunctions between eastern Asia and western North America in vascular plants highlight the biogeographic importance of the Bering land bridge from late Cretaceous to Neogene by Jun Wen, Ze-Long Nie, and Stefanie M. Ickert-Bond. Journal of Systematics and Evolution 54:469–490.

See the following topics at The Gymnosperm Database by Chris Earl:


Pseudotsuga menziesii

Pseudotsuga  menziesii subsp. menziesii 

Pseudotsuga menziesii subsp. glauca

Thursday, December 16, 2021

Pernicious Personification

Four hobbits are riding their ponies on a shortcut through the Old Forest. But the Forest keeps hindering them, forcing them down, down into a valley where they rest by a river under a large willow tree. One hobbit, who is cooling his feet in the water, suddenly finds all of himself in the water. When another hobbit pulls him out, he says, “… the beastly tree threw me in! I felt it. The big root just twisted round and tipped me in.” The personification of trees is a theme that runs throughout The Lord of the Rings. Generally, personification runs through old myths, fables, and literature, especially fantasy. Anthropomorphism, attributing human intentions and characteristics to objects, is something we all do. I can’t tell you how many times a tree has stuck a root up and tripped me while hiking. We all understand that these attributions are not literal. 

This kind of anthropomorphism also appears in nature writing. Some of this is innocent enough. It often adds some whimsy to the narrative and stimulates the imagination. Valerie Trouet does this in Tree Story, an engaging book on tree rings and what we can learn from them about climate, human history, and so much more. She talks about trees making wide rings when they are happy, but it’s clear that she doesn’t mean this literally. 

On the other hand, some nature writers do take their anthropomorphism literally. This is when anthropomorphism runs amok. For example, a recent book has become a controversial example of this kind of writing. It is The Hidden Life of Trees: What They Feel, How They Communicate by Peter Wohlleben. Just the title is enough to tell you where we are headed in this book. Inside, he talks about trees sending messages to their neighbors, tasting the saliva of insects, and screaming when they are thirsty. He defends these anthropomorphisms by saying that he wants to get his readers to value trees and treat them appropriately as beings with emotional lives. Surely we can see the value of trees just for what they are. And we will value them even more when we understand more about them, how they evolved, how they fit in an ecological system, and how they actually function in that system. We can see them as things of wonder and beauty without imposing human emotions onto them. 

Suzanne Simard describes her study of the forests of British Columbia in her book, Finding the Mother Tree: Discovering the Wisdom of the Forest. She tells of her studies of the complex relationship between trees and other life in the forest, especially the symbiotic relationship between tree roots and a network of mycorrhizal fungi. The fungi connect to the tree roots and branch out to collect nutrients for the trees. In return the trees send sugars to the fungi. This fungal network can connect to multiple trees and enable the transfer of nutrients from one tree to another. Simard has conducted important experiments on these relationships, especially on the transfer of nutrients from what she calls “Mother trees” to seedlings. She characterizes the Mother trees as talking to other trees. When experiments show that seedlings from the Mother tree thrive better than other nearby, unrelated seedlings, she characterizes this as Mother trees nurturing their young and says that Mother trees ‘recognize’ their own young. 

The research is groundbreaking and fascinating. But here I want to focus on the personification. Does it further our understanding? I argue that it does not. On the contrary, it distracts from our understanding. That is why I call it pernicious. When I read about research like this, I want to know why it is that the close relatives thrive more than the distant ones. What is the mechanism that allows them to do so? I suspect that it may be related to how the trees and the fungi evolved together. But when I’m told that the Mother tree recognizes her young, that tells me nothing about what the process might be. I can’t even make sense of that. But you say, “what about the evidence?” Let’s be clear: The evidence does not support the conclusion: It does not follow from that fact that the closely related seedlings thrive that the Mother tree recognizes them. This explanation is very simply not an explanation at all. 

Sometimes a metaphor can suggest a hypothesis that might lead to further investigation, but not in this case. Saying that the Mother tree recognizes her young misdirects us from any investigation of a possible relationship. Rather, we are directed to focus on the supposed intentions of the Mother tree and away from any investigation of the interactions between the roots and the fungal network.

I suspect that there is something in the genetic makeup of the tree and the fungi that might favor genetically similar seedlings. That is something we would want to investigate and would explain why the genetically distant seedlings might not  thrive as well. However, when we don’t understand the behavior of trees, we may be inclined to think of some analogous human action and ascribe intention and intelligence to it. But our lack of knowledge of the process is not evidence for the claim that trees are intelligent or have intentions. Again, rather than explain, this Anthropomorphism misdirects us from our search for an explanation. 

There are several lessons we can learn here:

First, beware of personifications given as explanations. They generally don’t explain.

Try to read personifications as innocent figures of speech. Sometimes they are.

Ask yourself: Does the personification lead you to consider an explanation? If not…

Be curious. Dig deeper, look for further explanations, or try to think of other possible explanations.

Oh, one more lesson: If you ever see a large willow tree by a river, do not sit under the tree and dangle your feet in the water!


See also

Pitfalls of Anthropomorphism: The Hidden Life of Trees

Facts or Fairy Tales? Peter Wohlleben and the Hidden Life of Trees

How Trees Talk to Each Other, Suzanne Simard - TED Tallk video

Do Trees Talk to Each Other?

The Intelligent Plant - The New Yorker

Tuesday, June 8, 2021

Focus on Redwoods

Redwood at Lady Bird Johnson Grove

The California redwoods are the most impressive conifers in the Pacific Northwest. They are notably the tallest trees in the world. They grow straight and tall to a height of over 300 feet. The world's tallest tree is a redwood named Hyperion, discovered in 2006 in Redwood National Park. It is 379 feet tall. Redwoods reach maturity at 500 years. The oldest is over 2200 years old. These giant, ancient trees also have many other exceptional, unique features.

Redwood needles are flat and lie flat on the twig like grand fir. But unlike grand fir, they point forward at an angle. Their growth pattern is optimized for growing in the shade. However, needles in the sun at the top look like the short leaves of the redwood’s cousin, the giant sequoia. When the old needles fall, the twig falls with the needles attached like two other relatives, the dawn redwood, native to China, and the bald cypress, native to the southeastern United States. 

The small, egg-shaped cones look like miniature giant sequoia cones. They are hard and woody with scales that look like lips. It’s amazing that the tiny seeds inside can grow to be the world’s tallest trees. However, redwoods have a backup plan for reproduction. They have epicormic buds in their trunk and roots. As long as the tree is healthy, the tree suppresses the growth of these buds. If the tree falls or is burned in a fire, the buds can sprout and grow. Then they become cloned trees, growing in a row on a fallen tree or in a circle around a stump. If the top of the tree is killed by fire, buds can sprout and send up multiple shoots, creating a virtual treetop forest. Moss and even soil can become part of this arial ecosystem, where birds, mammals, and reptiles thrive. The tiny red tree vole spends its entire life living in the top of a large redwood, eating its favorite food, redwood needles. However, the life of the red tree vole may be short, because it's a favorite food of the spotted owl.

The brown bark is similar to the bark of the giant sequoia, thick with deep furrows. It's quite soft to the touch, especially when wet. This thick bark is the redwood’s defense against fire and can be over 12 inches thick. 

In Oregon, redwoods grow only on the extreme southern coast near Brookings. The northern-most sites are in two groves along the Chetco River. Redwoods extend from Oregon to the central California coast, but the tallest trees are in northern California. Redwoods once had a much larger distribution across North America and even Europe and Asia. You can see a petrified redwood stump at the Florissant Fossil Beds National Monument in Colorado. 

The redwood was initially classified in the genus of the bald cypress and given the name Taxodium sempervirens in 1824. In 1847 it was placed in a new genus, Sequoia and given its present scientific name, Sequoia sempervirens. Sequoia is named after Sequoyah, the Cherokee who created a writing system for the Cherokee language. Sempervirens means evergreen. 

Most of the extensive redwood forests have been logged over the last 150 years. The largest living trees are now preserved in state parks and Redwood National Park. Managed redwood plantings on private land now produce the lumber for many uses. The wood is light, strong, and resists decay. Its beauty and color make it a favorite for siding, decking, fencing, and lawn furniture.

Redwoods at Hoyt Arboretum

You can find a planting of 90-year-old redwoods at Hoyt Arboretum in Portland. To find some larger redwoods, go to Brookings on the southern Oregon Coast. To find the tallest redwoods, you’ll have to go on to California, where you can see them at Redwood National ParkMuir Woods National MonumentJedediah Smith Redwoods State Park, and other state parks along the California Coast.

Redwoods may have ranged farther north along the Oregon Coast. You can see a large stump of a redwood on the beach south of Waldport at what is often called Big Stump Beach. According to a recent study this stump likely grew in this location, rather than being deposited on the beach from the ocean. It is located ¼ mile north of the beach access at Wakonda Beach. 

Redwood stump at Big Stump Beach

As the climate warms, more redwoods may be moving to Oregon, with the help of tree planting activists. Already, volunteers have planted some seedlings on the north slope of Humbug Mountain near Port Orford. These plantings may help combat the climate warming that led to the planting. A redwood forest stores more carbon per acre than any other ecosystem. So, planting more redwoods is an incredibly good idea.


See also

Redwoods at the Gymnosperm Database 

Redwood at Wikipedia 

Epicormic shoot at Wikipedia 

Florissant Fossil Beds 

Mystery in the Sand: Big Stump Beach 

Potential Late-Holocene Disjunction of Sequoia sempervirens on the Central Oregon Coast

Could clones save California’s endangered redwoods — in Oregon?