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.

Wednesday, October 11, 2017

Forest Fires

Recently, the Eagle Creek fire in the Columbia Gorge burned over 48,000 acres. It was disheartening to see so many beautiful trees along familiar trails go up in flame. But it also has been an opportunity to reflect on the nature of forest fires and their effects on forest ecosystems. Here are some reflections.

Forest fires happen. Well, accidents happen, too. But we try to avoid them. We try to avoid forest fires, too. And for the past 100 years, we have aggressively tried to put them out when they do happen. We had good reason to do so. After all, it is a disaster when a forest fire also burns down our house, or when a fire burns trees we were about to use for lumber to build houses. However, when I say that forest fires happen, I want to think about them differently. I want to think about forest fires in a natural forest. The key to thinking about forest fires is that in nature, forest fires happen. That is, forest fires are a natural, recurring event, usually caused by lightning. 

What does it mean? Now, let’s think about the consequences of recurring forest fires: If forest fires are a natural occurrence, then it should be no surprise that the forest has adapted to these fires. And this is just what has happened.   Trees have adapted to deal with fire in different ways. Some grow thick bark that protects them from fire. Others wait for a fire to release their seeds. These seeds are the key to generating a new forest.

Fire is necessary. Forests have not only adapted to tolerate fire. Fire is necessary to the healthy development of the forest. We often think of forests growing to their final mature state and living in perpetuity as old growth. We celebrate old growth as the ultimate state of a forest. We love the huge, mature trees and the diversity of life in a mature forest. However, such a forest is not sustainable. It may live in this mature state for hundreds of years, but eventually it will be altered by fire or some other disturbance. So it’s no surprise that some tree species not only tolerate fire, but depend on it. For example, Douglas fir needs bare earth created by a hot fire for its seeds to germinate. Trees that wait for fire to release their seeds also depend on fire. Many forest types depend on a large fire disturbance to regenerate. 
New life after a fire
Some trees depend on smaller fires to maintain the nature of the forest. For example, ponderosa pines have thick bark that resists fire. Not only do they survive frequent fires, but they depend on those fires to suppress competing vegetation. These fires are necessary to maintain the open pine forest. When we suppress the fires as we have done for over a century, competing shrubs and trees grow and provide so much fuel that, when a fire starts, it burns so hot that it kills even the large ponderosas. In the ponderosa pine forests and many other forest communities, fire suppression has actually caused larger and more destructive wild fires.

Forest ecologists now recognize that fire is a natural and necessary part of a forest ecosystem. So how should we think about the recent fire in the Columbia Gorge? It’s natural to think that our beautiful forests have been ruined. No one wants to hike through such a scorched and destroyed landscape. Well, we can take heart that not all the area the fire touched has been torched. And although some areas appear to be devastated now, they will regenerate. I saw this three years after the Dollar Lake fire on Mt. Hood. We can look forward to observing the same results in the Columbia Gorge. There is much we can learn about a forest when we see how it recovers from a fire. 
Three years after the 2011 Dollar Lake fire on Mt. Hood
Not all fires are natural. On the other hand, the Eagle Creek fire should give us pause. It is significant that this was not a natural fire. It was not caused by lightning. It was, rather, caused by teenagers setting off fireworks. So why is that important? First, the fire was started at the bottom of a canyon. This enabled the fire to quickly race up the steep slope of the canyon and spread from there. Lightning fires are more frequently started on ridge tops at higher elevations where the forest is thinner so the fire starts more slowly. Human-caused fires have also increased the frequency of wildfires. A recent study found that humans started 84% of wildfires in the U. S. over the past two decades. This raises the frequency of wildfires. Natural systems adapted to naturally-caused fire will not easily recover from the increase caused by human-started fires.
Eagle Creek Fire Soil Severity Map
Fire and Global Warming. Now we are faced with another challenge to our forests that is also human caused: Climate warming is changing the behavior of these fires. Warmer temperatures have caused the forests to become increasingly dry in the hot summer. Snow is melting sooner, creating a longer fire season. Over the past 40 years wild fires have become more frequent and more destructive. Wildfires may the biggest threat that our forests face in a changing climate. 

Controlled fires. One strategy for dealing with wildfires is to set smaller controlled fires. The controlled fires remove the excess fuel form the forest, allow the forest to recover, and help prevent hot-burning wildfires. People often object to the smoke caused by controlled fires, but wildfires produce about 10 times the amount of smoke per acre compared to controlled fires. Controlled fires, by their nature can be set at times when weather conditions are conducive to good smoke dispersal and when the winds blow the smoke away from populated areas.

What can we do? We can speak up in favor of forest practices based on recent research for managing forests as an ecosystem that naturally includes fire. This may include the use of controlled fires in some cases. We can point out that these fires are healthy for the forest and healthier for people who live nearby. And most of all, we can avoid starting fires in dry canyons that all too often become destructive wildfires.

Sources and More Info.
Human-started wildfires expand the fire niche across the United States
How Will The Wildfires Of Today Fuel The Fires Of Tomorrow?
Western Wildfires and Climate Change
Eagle Creek Fire Soil Severity Map
After the Dollar Lake Fire

Sunday, March 12, 2017

On Conifer Names

Botanical names seem to have a special status in our language. When we know the name of a tree, we often feel like we have gained a special knowledge of that tree. Many names describe the tree or tell you where it grows. Some tell who discovered it. So learning the name of a conifer often does tell you something about that species. More importantly, learning the names forces you to look more closely at the different characteristics of each tree so you can distinguish it from other similar ones. Learning the names of the conifers is not the be all and end all of knowledge, but it marks the beginning of a relationship. It allows you to become acquainted. Deeper knowledge comes later when you can take the time to observe more carefully and completely.

Most conifers have two types of names: A common name and the scientific name. A good place to start is with the common names.

Common names
Douglas fir - Pseudotsuga menziesii 

Like many other plants, conifers have names that are determined by common usage. Sometimes a conifer will have several common names used in different regions. Learning the common name is an easy way to identify a tree. The names are familiar and easy to remember. However, common names can be misleading. For example, none of the native Oregon cedars are true cedars. Cedars are native to the Middle East and the Himalayas. They are in the pine family and appear to be cousins of the firs. When Europeans came to North America, they encountered trees in the cypress family that had wood like the wood of the Old World cedars. So they naturally called them cedars. Many conifers get their common name because of the nature of their wood. It's not so surprising that people would name things based on the use they make of them.

Many trees called pines are not really pines at all. In the nineteenth century, English botanists circled the globe looking for new conifer species. They often called anything with needles on it a pine. Even Douglas fir was called a pine at one time. The Norfolk Island pine you find in stores each December is not even in the pine family. And the rare Japanese umbrella pine isn't in the pine family either. The Norfolk Island pine is in the Araucaria family in the same genus as the monkey puzzle tree. The Japanese umbrella pine is the only species in a family of its own.

Western hemlock - Tsuga heterophylla
Some writers have attempted to mitigate the misleading nature of common names by writing them differently, for example, "western redcedar," "Douglas-fir," and "Port-Orford-cedar."  But these strained artifacts don't really mitigate the confusion. The spoken name sounds the same. Even the written names don't convey the intended information. Any normal person seeing "redcedar" in print would still think that it's a cedar. And the names still don't tell you what genus or family the trees belong to. We should just realize that common names are not scientific names. In fact, one reason we have scientific names is to clear up this kind of confusion. If we want to use a name that correctly identifies the scientific classification of a tree, we will have to learn the scientific name.

Scientific names

Each conifer species also has a scientific name. Why learn the scientific name? These names give you an unambiguous way to identify a species. These names are assigned and agreed to by botanists based on rigorous classification of each plant. Each species is assigned to a general grouping or genus and given a unique species name. The names are Latin or at least given a Latin ending. The name for a species written as Genus species, written in italics with the genus name capitalized. For example, the scientific name of grand fir is Abies grandis. This name is universal throughout the world, no matter what language is spoken.

Grand fir - Abies grandis
As a practical matter, knowing the scientific name usually tells you something about the tree. For example, the name of western hemlock is Tsuga heterophylla. Tsuga is Japanese for hemlock. And heterophylla means variable leaves, which aptly describes western hemlock needles. Also, if you want to learn more about a tree, it helps to know the scientific name. Much of the scientific literature references species by the scientific name. Familiarity with these names will help when you see them in scientific writings.

Western red cedar - Thuja plicata
Even though scientific names give us a more precise way to identify each species, that's not to say that there's no confusion with these names. They may change. Science is not static. As botanists learn more about a tree, they may change its classification to a different genus. These changes generally generate a lot of discussion among the experts and confusion for the rest of us. Such a discussion has been raging about the classification of Alaska cedar. It was in the genus Chamaecyparis, the same genus as Port Orford cedar. Recently someone proposed putting it in a new genus called Xanthocyparis. Others have countered, saying it should be classified as Callitropsis or Cupressus. And some are proposing that all the Cupressus that are native to the New World should be placed in a separate genus called Hesperocyparis. Many other names have changed over time. Botanists had a terrible time classifying Douglas fir. Its name changed 21 times before they finally settled on Pseudotsuga menziesii.

Note that scientific names can also be misleading. For example, the scientific name of incense cedar is Calocedrus decurrens. The genus name means "beautiful cedar." Even the scientific name suggests that the species is closely related to the genus Cedrus, which it is not.

Getting Started

The photos above show the common conifers found at low elevations (below 2000 feet) in northwest Oregon. Look for these when hiking in Portland's Forest Park and other nature parks nearby.

Take some time to learn the names of our native conifers. It will help you become acquainted with them. Given some time and attention, you may even become friends with some of them.

For more help identifying our native conifers, go to Northwest Conifers.

Tuesday, March 7, 2017

Will Conifers Weather Global Warming?

Recent posts on this blog looked at how conifers survive the snow and cold. As increasing carbon dioxide in the atmosphere causes climate warming, cold may become the least concern for our forests. But how will conifers deal with the fact that the climate is getting warmer? As with everything related to the life of living things, it's complicated. But we can see some of the effects of climate change because they are happening now. And we can see some future potential outcomes just by understanding something about the lives of trees and how they react to their environment.

At the outset, it is important to remember that, like all living things, conifers growing in the natural environment are adapted to the climate conditions where they are. Each species is adapted to survive where it grows. In the Pacific Northwest, it has taken thousands of years for our forests to adapt to the current climate.

Going up north. One response to warming climate is to move to where it is cooler. Birds can fly to cooler temperatures in the north. Even mammals can move up slope to cooler locations in the mountains. But these options can be a problem for trees. Roots do not make good legs. Even so, successive generations of trees can move as each generation distributes its seeds a few hundred feet. Yes, trees can migrate over long distances, but it may take thousands of generations and millions of years. When climate change is rapid, migrating trees cannot keep up.

Trees marching up Mt. Hood?
Migrating up slope also can present significant problems. The space gets smaller as you near the top of the mountain. And if it becomes too hot for you at the top, you just have nowhere to go. Migrating north can present barriers as well. Mountains can be a barrier, as can rivers, lakes, and even oceans.

Adapting. Natural selection enables trees to adapt. When conditions change, the genetic variability in a population will enable some trees to survive and pass their genes to the next generation. In this way, a species can adapt to a changing climate in place, but like migration, this process could also require thousands or millions of years. Trees cannot readily adapt to rapid climate change.

Are we then putting our forests in danger by causing global warming? Well, the answer to that is complicated, and varied. The temperate forests of the Pacific Northwest will likely be less affected by climate change than those in the southwest U.S. Also, the consequences of climate change for forests is not just about rising temperatures. There are related factors that may more seriously impact our forests.

Vista Ridge fire on Mt. Hood
Drought.  As the climate warms, weather patterns change. Most seriously, rainfall patterns change. Some areas will get more rainfall. Some will get less. Entire forests may be plagued by drought. In these forests, tree species that are drought intolerant will not survive. Mild winters also contribute to summer drought. Winter snowpack stores water that melts in the spring and provides water for growing trees. However, warmer temperatures bring rain in winter instead of snow. The runoff comes early, and trees are left high and dry in the summer.

Wild fires. Drought-stressed forests are subject to an ever increasing risk of wild fires. With increasing drought, fires burn hotter and are more destructive. We have already seen recent devastating wild fires all over the western U.S.

White pine blister rust is killing 
pines on Mt. Hood
Insect invasions and disease. Trees weakened by drought are also vulnerable to insect invasions and disease. Winter cold can help keep insect invasions in check. But with warmer temperatures, the insects can survive the winter and attack forest trees in force the following summer. Recent mild winters have enabled the mountain pine beetle to destroy millions of acres of lodgepole pine and ponderosa pine forests in western North America.

More carbon dioxide. One mitigating factor for forests and other plants would seem to be the increasing levels of carbon dioxide in the atmosphere. The very thing that is causing global warming could be a boon for our forests. They use carbon dioxide and store the carbon in root, limb, and their massive trunks. Perhaps we can look to forests to store carbon and help prevent more global warming. However, this scenario may not pan out as well as you might think. Just as trees are acclimated to their climate, they are also acclimated to the amount of carbon dioxide in the atmosphere. They won't necessarily grow faster if carbon dioxide concentrations are higher. Other factors often limit growth. Some experiments have shown that increasing carbon dioxide levels does increase production in some conifer species. Others, not so much. Furthermore, forests decimated by drought, wild fires, and disease won't benefit at all from increased carbon dioxide. Thus, our efforts to preserve forests to prevent climate change can be undermined by the climate change we have already caused.

Forest conservation. One thing is clear: Preserving our forests is important. They can be a significant repository of carbon. Forest destruction only adds to the rising carbon dioxide in the atmosphere. How we protect forests from the effects of climate change is not as clear, but much research has been done. Some work is being done to develop trees that are resistant to disease and can tolerate changes in climate. Foresters are planting trees in new locations where they can thrive. Yet, more research is needed to determine the effects of the changing climate on forests and develop ways to help forests adapt to change.

How can we help? We can support restoration and reforestation efforts. Planting trees is good exercise, too. We can also reduce our consumption of fossil fuels by avoiding travel in fuel-burning cars and airplanes, and instead opting to travel by electric cars, bicycles, and our feet. We can make other lifestyle choices that leave a smaller carbon footprint. We can live more simply and install solar panels on our houses. We will have a smaller impact on our planet, and the the trees in our forests will be happy.

See Also

Climate change’s effects on temperate rain forests surprisingly complex

CNN:Global warming threatens forests, study says

Tuesday, February 7, 2017

Why Is the Climate Warming?

Just about everyone realizes that the earth’s climate is warming. If you haven’t seen it, here is the chart on global temperatures released by the National Oceanic and Atmospheric Administration in January 2017:

Source: NOAA

There is some variability up and down, but the trend is clearly up, and quickly accelerating. It doesn’t seem like much, but we can clearly see the effects of the warmer temperatures, including shrinking ice sheets, declining Arctic ice, and retreating glaciers all over the world. As a result of shrinking ice sheets, retreating glaciers and warming oceans, we are seeing rising sea levels. Even people who were skeptical of global warming are coming to realize that the temperature of the earth is rising. Now the question is: What is causing these rising temperatures?

Scientists have investigated several possible causes of warming, but their research has determined that only one cause explains the accelerating rise in global temperatures. The reason that the planet is getting warmer is due to the rise in greenhouse gasses, primarily carbon dioxide (CO2). Popular discussion in the media might lead you to think that the idea that these gasses could lead to rising global temperatures is a recent claim, but this is not the case. This relationship was proposed in the nineteenth century. Scientists were investigating the relationship between CO2 concentrations in the atmosphere and temperature. They theorized that increasing CO2 would cause the temperature to rise. The test of a scientific theory is whether or not its predictions turn out to be true. Laboratory experiments verified that CO2 and other gasses do act as a greenhouse gas. More importantly, we have been conducting a 100 year experiment that tests this theory on the earth itself. Sadly, it has turned out to be true. As atmospheric CO2 levels have increased, so have world temperatures.

A good scientific theory doesn’t just make predictions. We expect that the theory should explain a phenomenon. In this case, we want to know why temperatures increase when CO2 levels increase. Broadly speaking, the greenhouse effect works like this:
  1. The sun warms the surface of the earth.
  2. Some of this heat is radiated back toward space.
  3. Some of the heat that is radiated toward space is absorbed by molecules of greenhouse gasses.
  4. Greenhouse gas molecules then radiate some of this heat back to the earth.

Source: NASA

Now you might wonder, why doesn’t the radiated heat from the earth just pass through the greenhouse gasses like the initial heat radiation from the sun? The answer is where this theory really gets interesting. The radiation from the sun is mostly visible light and ultraviolet radiation. The shorter wavelength of this light passes through the greenhouse gasses. The radiation radiated back toward space is infrared radiation. The wavelength of infrared radiation is longer and more likely to hit the large molecules of greenhouse gases.

Source: NASA

Scientists have also determined the individual wavelengths absorbed by different greenhouse gasses. This enables them to measure how much each gas contributes to the greenhouse effect. You can read about that here.

Finally, research has shown that the reason that greenhouse gasses, and especially CO2, have increased significantly over the last half-century is due to the burning of fossil fuels. If we want to prevent runaway warming in the next century, we need to quickly develop alternative sources of energy.

More Info

The NASA and NOAA websites have enormous amounts of great information on climate change. At least it is still available as of February 6, 2017.

Monday, January 16, 2017

How Do Conifers Survive the Snow?

Snow is not friendly to trees, as we have seen, with the recent snow in the Portland area, which brought down limbs and entire trees. We see how destructive snow can be to trees, yet when we go to the mountains we see trees thriving there where the snow accumulates to many feet every winter. How is it that the trees in the mountains survive these mountains of snow?

First, we can notice that the trees growing in the mountains are not the same species as those we typically see growing in the lower elevations. Secondly, we have to remember that trees adapt to the environment that exists where they grow naturally. Several important adaptations have enabled conifers to survive deep snow without limb breakage. 

Conifers growing near the timberline show the most extreme adaptations to heavy snow. If you drive up to Timberline Lodge on Mt. Hood and look at the trees growing there, the first thing you might notice about them is that they grow as narrow spires with very short limbs. Other adaptations include drooping limbs that shed the snow and flexible limbs that bend without breaking when weighted down with snow.  

Subalpine Fir
Perhaps the most iconic of the conifers growing at the timberline is subalpine fir, which adopts the form of the Eiffel Tower. It is one of the more photogenic trees at the timberline, with tall spires pointing skyward. It avoids limb breakage by keeping its limbs close to itself. The short limbs don’t collect much snow on them, and the snow that does collect doesn’t get much branch-breaking leverage.

Pacific silver fir has slightly longer limbs, but they are pointed down where they can shed snow. Even when snow accumulates on the limbs, their orientation prevents breaking.

Pacific Silver Fir
Another strategy is to just bend under the burden of the snow. Mountain hemlock is fairly adept at this technique. It also tends to have shorter upper limbs than many other conifers. In the most extreme conditions, mountain hemlock has another trick: It stays low. At the highest elevations it grows as a low shrub. The weight of the snow can bend it to the ground, where it stays until the snow melts in the spring. This bendable habit also gives mountain hemlock an alternate way to reproduce. Limbs weighted down to the ground can take root. You can see patches of mountain hemlock growing near the timberline that reproduce in this way.

Whitebark pine is even more bendable than mountain hemlock. The branches of whitebark pine simply bend with the weight of the snow. In fact, its twigs are so bendable that you can tie one in a knot. That is one way to distinguish it from western white pine. Like mountain hemlock, whitebark pine branches can also take root when forced to the ground by snow.

Mountain Hemlock
Limber pine, which grows in the Wallowas and Rocky Mountains, is a close relative of whitebark pine. Limber pine is the king of bendability. Just in case you didn't know, its common name and scientific name (Pinus flexilis) both describe this feature. 

Conifers also benefit from the snow. Besides the obvious benefit of water from melted snow, the snow is a good insulator. It keeps the ground and roots from freezing in winter. Low-growing trees are also covered and protected from cold temperatures.


See also
How Do Conifers Survive the Cold?
Northwest Conifers: High-elevation Conifers
USFS: Mountain hemlock (Tsuga mertensiana)
USFS: Whitebark pine (Pinus albicaulis)

Friday, January 13, 2017

How Do Conifers Survive the Cold?

Snow on Noble Fir

December is the month of the fir, when it stands resolute, defying the wind and cold.  May is the month of the oak, when it springs to life in an outburst of vivid green.  October is the month of the Maple, when it blazes with the glory of the sun.

But in December, when the fickle oak and failing maple stand barren and leafless in the deepening cold, the fir flourishes, spreading its verdant needles in a steadfast display.  Even when winter covers its branches with snow, underneath the fir endures, a faithful testament to the promise of life.
Ken Denniston - December 1991

The recent cold weather in Oregon got me thinking about just how conifers are able to survive freezing temperatures. Even in the mountains where temperatures drop well below 0° Fahrenheit, conifers endure the cold, often showing no ill effects. When temperatures warm in spring, they, in turn, spring to life and put on new growth.

Ice on Douglas Fir
Freezing is not good news for most living things. It kills many plants and most animals. When living cells turn to ice, they are usually destroyed. Frost kills many crops and other plants. How is it, then, that some trees can survive the freezing cold temperatures of winter?

If you search the Internet and have the patience to wade through some very technical scientific papers, you will find a mountain of information about conifer cold hardiness. Here is a short, summary of what I was able to find and unscramble.

Conifers have developed two mechanisms to deal with winter cold: Freezing tolerance and freezing avoidance. 

Freezing tolerance: Plant cells can tolerate freezing by moving water out of the cell where it freezes without damaging the cell. The concentrated sap in the cell has a lower freezing point and remains in liquid form. This process also leaves the cells dehydrated. To survive, they must also be tolerant of dehydration.

Freezing avoidance: Plant cells can avoid freezing using a process called supercooling. This is a process in which water drops below its freezing point of 32° F. without turning to ice. How is this possible? Normally, when water freezes at 32°, it requires a seed particle. The ice crystals can then begin to form around the seed. This seed could be a tiny spec of some impurity. Water with no impurities can cool to about -40° and still remain liquid. Plants survive by maintaining pure water inside their cells.

Of course, there are limits to how well these strategies can protect conifers from freezing cold. This is why you won’t find any conifers growing on the north coast of Alaska.  

Not all conifers are equally cold hardy. You will see the cold hardy ones growing at the timberline in the mountains. Most conifers that you see growing at lower elevations cannot survive the cold temperatures near the timberline in the mountains. The US Department of Agriculture has developed a hardiness zone system and mapped these zones for the US, shown on the map below.

You can find the zone where you live here
You can find the hardiness zones for each conifer here

Even cold-hardy conifers can be damaged by extreme cold. The trees acclimate to the cold in the winter, but rapid temperature changes can still cause damage. New growth on trees and seedlings are more vulnerable to freezing damage. If a cold snap comes in the spring after new buds begin to grow, they can be killed. This happened to the new growth on many subalpine firs around Mt. Hood in the spring of 2016.

Note that there is considerable genetic variability in cold hardiness within a species. Trees adapt to the conditions where they grow. For example, Douglas firs growing at 5000 feet on Mt. Hood are more cold hardy than those growing in the valleys of the Coast Range. If you gather seeds from the low-elevation trees and plant them up at 5000 feet in the Cascades, they will not be able to thrive in that cold environment.

Hoyt Arboretum - January 12, 2017
More info.
“Mechanisms in Frost Survival and Freeze-Damage in Nature” by Marja-Liisa Sutinen, et al.  in Conifer Cold Hardiness, Ed. by Francine J. Bigras and Stephen Colombo, P. 90ff. Available here.