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Our Dynamic Forest

By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester

 

This year January brought us an unusually wet, heavy snow.  In my Lake Oswego backyard, it amounted to just over 7-1/2 inches of the white stuff.  The snow at Tryon Creek State Natural Area (TCSNA) was roughly similar.  As with so many other unusual events, it was a great opportunity to learn more about our forest.

 

The wet, heavy snow brought many changes.  Some that we humans, entranced with the visual wonder that is our forest, tend to regard as tragic.  But Nature may have a different view.  Let’s take a look at some of the things that happened.

 

Look out below! 

All kinds of trees fell down.  As shown in the photo below, the top snapped off from this red alder (Alnus rubra) growing near Red Fox Bridge.  You can see the top lying on the ground.  For the alder, this is a horrific setback, if not death.

Photo 1

Top of alder broken off near Red Fox Bridge.

 

However, the plants growing on the ground under this alder may have a different perspective.  I stood right over the alder trunk lying on the ground, pointed my camera upwards and took this picture of a significant hole in the canopy.

Photo 2

View of the sky where the alder fell down.

 

Do you suppose the plants growing on the ground are looking up and thinking, “Oh what a tragedy.  Now we’re going to be growing in full, life-giving sunlight, and we won’t have competition from the alder.”  No matter what kind of tragedy it was for the tree that fell down, many of the neighboring plants will be celebrating because of the extra sunlight they will be receiving.

 

And if the existing plants already on the ground aren’t able to jump in and take advantage of the newly sunny spot, rest assured that some new plants will.  The photo below shows numerous red alder seeds (two are marked with red arrows) on the Middle Creek Trail the very same day I photographed the broken alder.  Finding these tiny seeds in the forested area would be very difficult, but have no doubt, they are there!

Photo 3

Red alder seeds on the trail (green Douglas-fir needle at bottom provides perspective).

 

Death Cleanses the Forest

Perhaps you mourn the loss of so many good trees.  In at least some cases, your tears are wasted.  A storm like the one we had can be viewed in part as Nature cleaning up the forest.  For example, as part of a human cleanup effort, I spent some time cutting through the trunk of a western redcedar (Thuja plicata) that was lying across the Cedar Trail so the trail would become passable (see photo below).

Photo 4

Western redcedar stem lying across the trail (note pen for scale).

 

It was sad because it was a young tree, with potential to become one of the esteemed elders of the forest.  Or so I thought.  As I dragged some of the branches off the trail, I noticed the top of this tree (pictured below).

Photo 5

Dead top of the fallen western redcedar tree.

 

The top four to five feet of this tree had already been dead for some time.  So the real story was that this tree was already having problems of one kind or another, and the storm just ended its struggle.  Since it already had a dead top, its long term potential was not as great as I originally thought.

 

In another case, a very tall (about 115 foot) Douglas-fir (Pseudotsuga menziesii) fell down across the Old Main Trail.  This is another tree that I cleared off the trail (Note:  The clean-up work I did after the storm proved very educational.  You might want to give it a try!)  The top was forked due to some damage many years ago, as indicated in the picture below.

Photo 6

Fork-topped Douglas-fir on the ground after a heavy snowstorm.

 

But this is another example of a tree that was already in trouble.  The smaller branch on the right side of the picture shown above had been damaged many years before this year’s storm, as you can see below.

Photo 7

Broken, semi-rotten top end of one of the major stems on a Douglas-fir.

 

I sawed off the top 12” of this stub, and inserted a pencil into the soft rotten area in the center of the stem.  The results are shown below.

Photo 8

Pencil stuck in stub of tree trunk.

 

Photo 9

This is how far I could stick the pencil in.

 

I could easily stick the pencil a couple inches into the rotten wood.  I cut 2 more feet off the end of this stub, and was still able to stick the pencil about ½” into the rotten center of the branch.  Once the fungus gains this much of a foothold in a tree, it’s only a matter of time before it seriously weakens the tree.

So once again, the storm felled a tree that was already in trouble.

 

Dead Trees Can be Useful

And if you mourn for the dying trees, rest assured that not all of the forest inhabitants share your grief.  Bark beetles lay eggs under the bark, and their larvae start burrowing through and eating the soft nutritious tissues that are right under the bark.  Of the hundreds of species of bark beetles, at least some attack after the tree is dead.  These beetles leave the kind of tracks like those you can see after the bark has been removed from this branch collected at TCSNA.

Photo 10

Tracks left by bark beetles eating the soft tissues of the branches.

 

And of course, once insects get into a tree, can woodpeckers be far behind?  The photo below shows a heavily “wood-peckered” long-dead tree along Old Main Trail.

Photo 11

Heavily woodpecker-ed dead tree along Old Main Trail.

 

And Some Weird Stuff…

The snow also brought at least one unique observational opportunity!  Down near the creek in one area, I noticed that the snow had patches of yellow color.  (No, it’s not THAT!)  There were no animal tracks in this area, so I seriously doubt the yellow patches were from dogs or coyotes.  According to reports on the internet, yellow snow in this context is frequently the result of pollen getting mixed in with the snow.  Sadly, I got a picture, but never collected a snow sample for microscopic examination.  The storm was roughly at the time that some hazel (Corylus spp.) would be shedding its pollen, but I have no proof that’s what it is.

Photo 12

Yellow patches of pollen (?) on fresh snow near Beaver Bridge.

 

Assuming this is pollen, I have no doubt that pollen is shed like this on the ground every year.  However, it takes a snow covered forest floor before we will ever notice it.

 

Our Ever Changing Forest

Our forest is an ever changing ecosystem.  If we could see this forest in 400 years, much of it would look unfamiliar.  Most often the change is very slow, but a catastrophic event like a dramatic storm puts the changes in a time context we humans can relate to.  Enjoy our forest today, because when you come back tomorrow, it will be different.

 

 

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Looking Back and Ahead

Weather and Climate: Looking Back and Ahead

By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester

 

Talk about a double whammy! The Portland area, including Tryon Creek State Natural Area (TCSNA), has set an all-time record for December rainfall, and the 2015 United Nations Climate Change Conference has just wrapped up in Paris! Lots of people are thinking about the weather and climate now!

The growth, survival and distribution of the plants at Tryon Creek State Natural Area (TCSNA) are affected by a host of factors. These factors include climate and weather, but also things like soil chemistry, soil depth, the steepness of the slope the plant is growing on, and soil moisture holding capacity. Probably the two most important weather variables are temperature and rain fall. Most of the discussion around climate change has to do with increases in the mean annual temperatures. This is a good place to start, but perhaps inadequate to explain all the changes we might see.

 

So how might climate change effect our forest?

Climate change might affect TCSNA in many ways, for example, altering the species composition of the forest. I am in my third year of monitoring the growth and development of a variety of plants in my phenology study at TCSNA. In my monitoring I visit the same plants every week to ten days and record their status. Perhaps looking at some of the results might provide a peek into the future. One of the species that I am monitoring is Pacific waterleaf (Hydrophyllum tenuipes). As the waterleaf tends to form dense clumps, I am monitoring approximately a 3-foot diameter circle of plants at each of four separate areas, rather than just trying to track a single stalk.

Pacific waterleaf is a perennial plant, which sends new shoots up every year from rhizomes. Think of rhizomes as “underground stems”. The above ground shoots die back in the “off season” and only the roots and rhizomes persist from year to year. At TCSNA waterleaf is generally from 40 to 60 cm (16 – 24”) tall at maturity. These shoots die back sometime in the summer, generally after they have produced a crop of seeds.

1

Pacific waterleaf near Red Fox Trail

 

Reviewing the phenological records, the last two years have seen a lot of variability in the behavior of the Pacific waterleaf at TCSNA. The chart below indicates the presence or absence of waterleaf leaves at each of the four monitoring sites on a weekly basis.

Weekly Presence/Absence of Pacific Waterleaf at Four Locations at TCSNA over Two Years

2

Key:  Yellow = Waterleaf Absent; Green = Waterleaf Present;

Week 1 = first week in January, Week 26 = end of June, Week 52 = last week of December

The late-winter through early-summer growth is the time when the waterleaf is making the vast majority of its sugar to support the plant, AND when the plant is producing seeds. The second emergence of leaves is around weeks 40 to 45 (roughly October thru early November). This “second leafing out” produces leaves that tend to be fairly small and I’ve never seen this second leafing produce flowers, much less seeds. And, as you notice, there is a certain amount of “now you see it, now you don’t” with this second leafing out. In at least some cases, the second leafing out leaves are eliminated by a serious frost.

It is interesting to note that on the Middle Creek Trail, there is never a “second leafing out.” The major difference between the Middle Creek waterleaf patch, and all the others is that the Middle Creek patch is on a significant slope, and is more exposed to direct sunlight. All the other patches are on flatter sites. Thus, it may dry out sooner than the other patches, and not have the late-season water it needs for a second set of leaves.

Why are these years so different?

  • One thing that you can see immediately is that the green bar (indicating the presence of waterleaf plants) consistently ends earlier in 2015 than in 2014 for any given site. In 2015 the leaves disappeared on average 7 weeks earlier than in in 2014. This is a significant amount of time.
  • The seeds of the waterleaf mature approximately in mid-June, so in both cases the plants survived long enough to produce seeds, and nothing more. It is likely that the leaves which persist after seed production are producing sugars to help support the plant for the next growing season.

What could have caused that difference?

The contrasts in weather between 2014 and 2015 are dramatic. I think the weather data probably goes a long way in explaining this year-to-year behavioral difference.

First let’s look at the (Portland) air temperatures maximum and minimum for the years. In each chart, the highest average minimum or maximum air temperature is highlighted in color. Where the temperature for any month was more than 5° F higher than any other year, it is highlighted in red.

Average Daily Minimum Air Temperature – Portland

(In °F; higher year highlighted red)

Month 2014 2015
January 35.1 37
February 34.6 41.5
March 40.2 42
April 44.7 42.6
May 51.3 51.5
June 53.9 57.9
July 59.8 61.1
August 61.4 60.5
September 56.5 53.1
October 52.1 51.2
November 40.7 38.5
December 39.1

 

You can easily see that for most of the spring and early summer months, the minimum temperatures were higher in 2015 than in 2014. But that’s just the start. The next chart tells us even more.

Average Daily Maximum Air Temperature – Portland

(In °F; higher year highlighted in red)

Month 2014 2015
January 47.7 49.9
February 46 56.8
March 58 62.8
April 62.6 62.9
May 71.1 70.7
June 73.4 82.7
July 83.8 86.7
August 84.8 84.3
September 78.7 75.8
October 68 69
November 51.9 52
December 49.2  

 

Again, for most of the spring and early summer months, the average maximum daily temperature was higher to dramatically higher in 2015 than in 2014. The yellow-highlighted months are more than 5°F warmer than the comparable month in 2014. The average high temperature in June 2015 was almost 10° F higher than June 2014! This higher temperature would probably cause the plants to lose more water, produce less sugar, and grow less in 2015 than they did in 2014. But the icing on the cake is yet to come. Just take a look at spring/summer rainfall data (from the PCC Sylvania rain gauge station).

February through June Rainfall

(Inches)

Year Amount
2014 22.76
2015 13.42

 

Wow! The early growing season rainfall in 2014 was nearly twice what it was in the comparable time in 2015.

The “growing season” for Pacific Waterleaf in 2015 was both hotter and drier than it was in 2014. The result was that the above ground waterleaf shoots disappeared on average 7 weeks earlier. Yikes! A seven-week difference in leaf persistence is not trivial.

 

The future!

I can’t wait to see what kind of impact this has on waterleaf in the 2016 season.

Think of all the linkages that there may be between waterleaf and the other organisms in the forest. Possibly less food for waterleaf-eating insects, less cover for mice scurrying around looking for food, fewer waterleaf seeds for food, and possibly increased soil erosion from late summer rainstorms.

This is the story of just one species of plant, but it might foretell the challenges we face if climate change continues unabated.

 

 

 

Fire and Flood

Tryon Creek – A Place Made from

Fire and Flood

By Roland Begin, Volunteer Nature Guide

Eons before Tryon Creek rang with the sound of loggers’ axes, or the whoosh of a Chinookan arrow finding its mark in a deer, or even the flute-like song of a wren soaring up into ancient cedars – the forested canyon had been birthed by irresistible forces of plate tectonics and volcanic lava flows.

Subduction zone diagram modified from an image by José F. Vigil and Robert I. Tilling, courtesy of U.S. Geological Survey.

Subduction zone diagram modified from an image by José F. Vigil and Robert I. Tilling, courtesy of U.S. Geological Survey.

 

Over 200 million years ago (mya) all of Oregon was ocean bottom. Over the next 150 million years, as the Pacific ocean plate slowly subducted under the North American plate, seafloor and volcanic islands were scraped off onto the continental plate. Eventually, around 40-30 mya, a chain of islands plowed into the plate and began forming the Coast Mountains. These same ancient basaltic rocks, known as the Waverly Heights Formation, became the underlying strata of the Tryon Creek area – and can still be seen in a few places around the park today.

volcano

Eruption

The Columbia River Basalts

Over the succeeding 10-15 million years, uplift and erosion continued to sculpt the initially flat landscape – until about 15 mya a new phase of extraordinary volcanism began. Enormous vents in eastern Oregon tore open and began to pour out lava. Over thousands of years, unimaginable quantities of lava (known as the Columbia River basalts) flowed across the land, down the ancestral Columbia River, into the Portland basin and the Willamette Valley, and out into the ocean. But somehow it never over-topped the Waverly Heights basalts of Tryon Creek, making it a very rare place indeed.

The Boring Lavas

Meanwhile, the forest grew and evolved, different plant and animal species came and went, and countless years passed. About 1-2 mya, another volcanic phase occurred. This was the period of the Boring Lavas (named for vents near Boring, OR), where local volcanoes such as Mt Tabor, Cook Butte, and Mt. Sylvania erupted and poured yet more lava across the land. As it turned out, however, the flows from Mt Sylvania only impacted the western edge of Tryon Creek park – thus largely leaving the Waverly basalts once again untouched.

Boring_lava_allen_map

Missoula Floods

Ironically, even as those ribbons of fire flowed, the land was in the firm grip of an ice age, as it had been for a couple million years. Then, around 12,000 years ago, an enormous glacial lake in the vicinity of Missoula, Montana was being held back by a slowly warming and weakening ice dam. Ultimately, the ice dam failed, hurtling a 400′ foot wall of water, ice, and stone down the Columbia River toward Portland. By the time this torrent reached Tryon Creek, it was still 100′-150′ deep – scouring the soil back down to the Waverly basalts. This devastating flood wreaked havoc with forests and streams across the entire Columbia River watershed – and was repeated as many as 100 times!

flood

the floods

Since those long ago days, the forest of Tryon Creek has been comparatively tranquil – enabling a rich diversity of plant and animal life to flourish within its sheltering canyon. And today, with the blades of loggers and bulldozers also stilled, visitors can themselves enjoy the wren’s magical music, amidst this forested beauty which titanic forces of fire and flood have wrought.

IMG_3648

Tryon Creek forest

 

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