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.

Saturday, November 24, 2018

The Larch

Western Larch by Highway 35
We usually think of conifers as evergreen trees, and most conifers are evergreen. However, some conifer species are notable exceptions. They are deciduous. That is, they drop their needles in the fall and grow a new crop each spring. Most of these deciduous conifers are larches. Ten species of larch grow in the Northern Hemisphere, three are native to North America, and two grow in the Pacific Northwest. Western Larch (scientific name, Larix occidentalis) is the most common larch in the Northwest and the only larch native to Oregon. You may not notice the larches on your summer hikes in the Cascade Mountains, but in November, when the needles turn golden-yellow, they stand out like trees on fire. You can see them along Oregon Highway 35 north of Mount Hood Meadows.

Now, you may wonder, why do larches drop their needles in the fall? Other conifers growing nearby seem to survive the winter cold just fine with their needles intact. These conifers have adapted to the cold by moving water out of the cells in the needles, leaving a concentrate that acts like antifreeze, or by purifying the water in the cells so ice crystals can’t form even at temperatures well below freezing. The larches have adapted a completely different strategy. They just drop their needles in the fall and grow new ones in the spring. This enables larches to survive some of the coldest temperatures of any of the conifers, growing high in the mountains and in the northern latitudes of North America and Siberia.

Western larch
It takes a lot of energy to grow new needles every year. However, since the needles only have to last one season, they don’t need to be strong and durable. So less energy is needed to grow them. As a result, you will notice that larch needles are much more delicate than those of evergreen conifers. The same is true of the leaves on trees. Note how the evergreen leaves are thick and stiff compared to the delicate leaves on deciduous trees.

Western larch needles
Larches are easy to identify. The needles grow in bundles like a pine with about 25 needles in each bundle. In the Cascades, Western Larch grows mostly on the east side of the Cascade summit at elevations up to 6000 feet. It also grows in the mountains of northeastern Oregon and Washington, and in northern Idaho and western Montana.

Alpine larch (Larix lyallii) grows at elevations higher than Western Larch, near the timberline in the North Cascades in Washington. It also grows in the Rocky Mountains of Idaho, Montana, and Canada. 

Western larch is an important timber tree. The wood is nearly as strong as Douglas fir and is used for framing and finishing. Western larch is also a popular firewood in the Northwest. It is often called “tamarack” by wood cutters, a common name for the other North American larch (Larix laricna), which grows in the northeast United States, across Canada, and in central Alaska.

Japanese larch at Hoyt Arboretum
November is the time of the year to look for larches, when they display their fall colors. To see the larches at Hoyt Arboretum in Portland, start at the Visitor Center and walk west on the Fir Trail.

See Also
Fall Conifer Colors
How Do Conifers Survive the Cold?
Western Larch at Northwest Conifers

Sunday, November 4, 2018

The Elusive Fir Cone Mystery

Douglas fir cone
Did you ever wonder why you don’t find fir cones on the ground? Well, cones typically cover the ground under Douglas fir trees. But Douglas firs are not in the Abies genus, the genus of the true firs. Like many conifers, Douglas fir cones open in late summer or fall and commit their small, winged seeds to the wind. The seeds descend like little helicopters, where most of them become tasty morsels for chipmunks, juncos and other small birds. Some time later, the cones drop from the trees to the ground. This is why the ground under mature Douglas firs is usually littered with cones. 

Cone near the top of a noble fir

Unlike the Douglas fir, you will rarely see a cone under a noble fir. In fact, if you see any cones under a noble fir, they are likely cones from a nearby Douglas fir. If you look carefully at the top of a noble fir, you may see cones up there. But the cones don’t stay there forever. So what happens to all the noble fir cones?

Noble fir scale and long bract
Noble firs, like all the true firs, engage in extreme seed distribution. The cones don’t just open and distribute the seeds. They completely fall apart and let everything fall to the ground, seeds, scales and bracts, leaving only a narrow spike of the cone core on the tree. The winged seeds generally separate themselves from the scales and sail off in the wind. The scales usually fall closer to the tree. Although you won’t find intact cones on the ground, in late summer and fall, the ground under a noble fir is often covered with these cone scales, with the bracts still attached.

Grand fir scale with broad bract

When you see these cone scales on the ground, you can use them to identify the species of fir. Recently hiking the University Falls Loop Hike in the Coast Range, I noticed some scales had fallen onto the trail. Attached to the scales were long bracts that extended beyond the edge of the scales. These long bracts are unique to noble fir among the native firs of Oregon. All of the other native firs have much shorter bracts, which never extend beyond the edge of the scales. 

Pacific silver fir scale with tapered bract

Later on the University Falls Loop, there were some scales along the trail with bracts that were much shorter than the scales. These fell from a grand fir. Note the shape of the tip of the bract. Each species has its unique shape. Grand fir has a broad end with a narrow tip. If you hike above 5000 feet in the Cascades, you're likely to see Pacific silver fir and subalpine fir. Pacific silver fir bracts are tapered at the end and come to a point. Subalpine fir bracts are rounded with a small point at the end.

Subalpine fir scale with rounded bract

So, if you are out hiking in the fall, just look down. You may see the cone scales all over the forest floor. Then you will know what happened to the fir cones. Not only that, but you will be able to identify each of the firs by the distinctive bracts of each species. 

Occasionally, you will find a fir cone, or even several fir cones on the ground. If you do, you should step away from the tree. It’s likely that a Douglas squirrel is cutting them loose and letting them fall to the ground. Douglas squirrels have no time for chasing after loose seeds. They will cut a cone loose and then strip the scales and eat the seeds, or store the cone in a cache to eat later. A favorite of the Douglas squirrel is the seeds of the Douglas fir. They can strip the scales from a cone and eat the seeds in about five minutes, leaving only what I call a “cone cob.” If you see Douglas fir scales on the ground, you can be sure Douglas squirrels have been busy at that location. You can often see piles of these scales and the left-over cone cobs below the squirrel’s favorite spot for eating lunch.

Douglas fir scales and cone cobs

Tuesday, September 25, 2018

Andrews Experimental Forest

I had the great opportunity to visit the Andrews Experimental Forest east of Eugene, Oregon this summer. The HJ Andrews Experimental Forest is a 16,000-acre ecological research site, supported by Oregon State University and the US Forest Service.

The Andrews Forest was established in 1948. In the 1950’s, the research focused on increasing the “efficiency of forest operations.” At that time, forestry was viewed as a form of farming. Just as the corn farmer grows crop after crop of corn, the forester grows crop after crop of trees. The question was: How do we use science to maximize the tree harvest? Of course, natural forests in the Pacific Northwest didn’t grow as crops. The trees here grew to be large and old. But what about these old-growth forests? They were considered very inefficient, in fact worse than inefficient, producing no new logs. First they needed to be cut down. Then efficient tree farming could begin. The process was:  Plant new trees, usually Douglas fir, grow them for 60 years, harvest them by clear cutting, repeat. This was the new “scientific” approach to forestry, which at least replaced the devastating cut and run forestry that removed forests all across the country, starting at the East Coast. Still, this new approach to forestry was focused on maximizing timber production.

Lookout Creek in the Andrews Forest
However, the researchers at the Andrews Forest also began to study the workings of a naturally growing forest. It is as if they had just discovered something that Henry David Thoreau had written 100 years earlier: “Would it not be well to consult with Nature in the Outset? For she is the most extensive and experienced planter of us all” (from “The Succession of Forest Trees.”) It is this focus on how a natural forest grows and how the various organisms interact, grow, and change over time that has occupied the scientists at the Andrews Forest. This new research has led to some amazing discoveries and a new understanding of how to manage a forest ecosystem.

Ancient Douglas firs in the Andrews Forest
Jon Luoma’s wonderful book, The Hidden Forest, tells the story of the research at the Andrews Forest. Some of the most interesting research reveals how different species in the forest work together for mutual benefit, an arrangement called symbiosis. Here are some fascinating examples.

All plants need nitrogen to thrive. A young forest gets nitrogen from nitrogen fixing shrubs. Red alder trees, which often are the first trees to grow in a new forest also have nitrogen fixing bacteria in their roots. However, as a forest matures, conifers grow to shade out the shrubs and even the alders. By the time the forest becomes mature, all these nitrogen fixers are gone. So, where does a mature forest get the nitrogen it needs? This mystified scientists for a long time. They didn’t find the answer until a team at the Andrews Forest used ropes to climb into the top of a Douglas fir tree. What they found 200 feet above the ground was an abundance of lichen growing on the branches. The lichen they found is lettuce lichen (Lobaria oregana). Testing showed that this lichen was full of nitrogen. Much of the lichen eventually falls to the forest floor allowing the nitrogen to enrich the soil. Without the lichen, an old-growth forest probably could not exist. In return, the lichen doesn’t ask for much, just a place to live up in the abundant sunlight of the forest canopy.

Lichens themselves are an interesting study in symbiosis. A lichen is not a single organism. It is a composite organism made of algae and fungi living in a symbiotic relationship. The algae perform photosynthesis and supply energy to the lichen. Threads of fungi provide structure keeping it all together, gather water and nutrients, and attach to the tree where the lichen grows.

Another fascinating discovery was finding fungi living inside apparently healthy conifer needles. Why didn’t the fungi harm the needles, and just what were the fungi doing there? Well, trees have a problem with defoliating insects. Unlike short-lived plants, trees live too long to react to evolving short-lived insects. It turns out that these fungi have a symbiotic relationship with the needles. In exchange for the energy supplied by the needles, the fungi protect the needles by creating compounds that poison the defoliators. If the defoliators develop a resistance to the poison, the short-lived fungi can quickly change to create new, effective poisons. It’s a constant evolutionary race, not unlike the race between new strains of disease and the pharmaceutical companies that must create new forms of antibiotics, although the fungi don’t make billions of dollars for their services.

Over 100 years ago, scientists discovered another symbiotic relationship 200 feet below in the root systems of the trees. While researching how to grow truffles, a scientist discovered that threadlike tendrils attached to the truffles were connected to the roots of trees and other plants. These are the fungi that produce the truffles. He also discovered that seedlings with these fungal connections grew much faster. Now we know that these fungi get nourishment from the tree. In return, the fungi collect water and minerals that feed the root system of the tree.

Douglas squirrel munching on a fungus
In the 1970’s scientists at the Andrews Forest discovered more remarkable connections in the ecology of the forest, not just between the fungi and trees, but also between the fungi and small mammals. Voles, chipmunks, squirrels, and mice, love truffles and other fungi. For some, it is an important part of their diet. It’s no surprise that squirrel poop is chocked full of the reproductive spores from the fungi, which, of course, these small mammals distribute all over the forest making their own little contributions to the forest ecosystem. In their turn, the trees provide habitat for the mammals both when the trees are alive and especially when they’re rotting on the ground. Voles, for example, depend on these rotting logs. The rotting logs, then, become an essential part of the forest ecosystem, not just providing living quarters for the voles, but food for insects and other organisms as well. Eventually, nutrients in the log are recycled back into the soil. These factors have led researchers at the Andrews Forest to re-assess the old forest practices of clear-cutting and removing the dead material from the forest floor.

These and other discoveries at the Andrews Forest led to a new approach to forest management based on their studies of naturally growing forests. If Thoreau were alive today, he would say, “Well, it only took you 100 years to figure that out.”
Andrews rain gauge with baffles to increase accuracy 
My rain gauge
The two-day workshop I attended at the Andrews Forest was hosted by the Oregon Season Tracker Program, a joint project of the OSU Extension program and the Andrews Forest. The Oregon Season Tracker Program enlists volunteer citizen scientists to collect and record precipitation and plant phenology data. Daily precipitation is easy to record using a standard rain gauge like the one above. We report the precipitation to the CoCoRaHS Web site.

Plant phenology observations enable us to track the changes in plants as they respond to seasonal changes and variations in weather and, in particular, climate change. We report our phenology observations on the Nature's Notebook site.

 More Andrews Forest photos
Stream monitoring station

Western hemlocks

Temperature monitor

Experimental rain gauges


More info