Monthly Archives: May 2015
Is This an Early Spring?
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
If I’ve heard it once, I’ve heard it a hundred times in the last couple of months – “This is really an early spring!” By “early spring” most folks are referring to a year when leaves and flowers appear earlier than “normal.” The conversation quickly moves to “How early?” and this is where some data would be handy. Welcome to phenology!
What in the world is “phenology?”
Phenology primarily deals with the relationship between climate and the timing of biological phenomena like flowering in plants or bird migration. The starting point of phenology is creating long-term records of when certain biological events occur. Using these records, one can then make statements about “early springs,” “late autumns,” and other periodic climate-related events.
I started keeping phenological records for Tryon Creek State Natural Area (TCSNA) in mid-spring of 2013. Since then I’ve made observations every 7 to 10 days on about 70 specific, individually tagged plants.
Cut to the chase. Is this an “early spring?”
Since the Tryon Creek Phenology study is new, the question I’m really answering is “Was 2015 an early spring compared to 2014?” After studying the records for the study plants, I found there are really three answers.
Answer #1: Yes, it was an early spring!
Based on 8 Indian plum (Oemleria cerasiformis) plants that produced flowers both years, in 2014, the average date for the opening of the first flower was March 10th. The average date for opening of the first flower in 2015 was February 18th, a difference of 20 days! For the flowering of Indian plum, 2015 was an “early spring” for sure.
Vegetative bud break in red elderberry (Sambucus racemosa var. racemosa) was also earlier this year. Based on 3 plants, the average date of leaf emergence in 2014 was February 23rd, while this year it was February 14th, a difference of 9 days.
Finally, four Pacific waterleaf (Hydrophyllum tenuipes) plants produced visible flower buds on March 29, 2014, but this year, they all produced flower buds 11 days earlier, on March 18th.
Answer #2: It was a normal spring!
Looking at the date of bud break of 10 Indian plum plants, a different story emerges. In 2014 the average date when leaf tissue extended beyond the bud scales (as seen in the photo below) was February 4th. This year, that date was February 1st, just three days earlier. This is approximately the amount of experimental error one might expect in this study. In other words, this difference might be real or it might be a consequence of the length of time between measurements.
The particular vine maples (Acer circinatum) I monitored, rarely produced flowers, so I had to rely solely on the date of first bud break. I checked the date when the leaf tissue extended just 2 to 3 mm (about 2/10ths of an inch) beyond the red bud scales. In the picture below is a vine maple bud that is at this stage. The leaf tissue at this point has a whitish, hairy appearance.
On average, the six plants that were examined in both 2014 and 2015 reached this stage on March 23rd in 2014, and March 21st in 2015. This is a difference of just 2 days. In this study, that is within experimental error of being identical. So at least for vine maple, there was no difference in time of bud break between the two years.
Answer #3: It was a late spring!
Some of the plants seemed to be a little later this year than last. For example, based on 4 salmonberry (Rubus spectabilis) bushes, in 2014 the leaves first extended beyond the bud scales on February 11th. This year, they were a week later, with the leaves not extending beyond the bud scales until an average of February 18th.
Early, Normal & Late? What’s the deal?
For the vegetative and flower buds of native plants in temperate regions to open up (“break”) and begin growing, two things need to happen. First they need to experience cold (termed “chilling”), and second, they need to experience warmth (termed “forcing”). In that order! Why do the plants do this? While the buds of most plants are pretty tough, the young shoots are relatively delicate. So the plant faces two challenges in the timing of bud break.
Challenge #1: The plant doesn’t want the buds to break too early and start growing just before a big freeze hits. The plant “knows” that even after a short warm spell in December, it could turn fatally cold in January.
Challenge #2: The plant doesn’t want to start growing too late in the year, like mid-July! Starting growth too late means it would miss out on some really nice growing weather in late spring and early summer.
These challenges have been met by plants developing a requirement for a certain number of hours of chilling and then forcing. The definition of “chilling” depends upon which study you read, but generally temperatures in the range of approximately 32 to 50° F count as “chilling.”
“Forcing” is the amount of warmth a plant receives prior to bud break. Typically, any temperature over 50° F counts as forcing. Anytime the temperature is over 50° for an entire hour, the plant is credited with 1 forcing-hour.
The diagram below shows the basic relationship between “chilling,” “forcing,” and bud break. The black curve between the pink and green areas represents the combined amount of chilling and forcing that are needed before a plant can start to grow. The general rule is that the more chilling a plant gets, the less forcing it needs to bud break. Different species of plants have chilling/forcing curves with different shapes. Give yourself bonus points if you noticed that when a temperate region plant receives no chilling, there can never be enough forcing to cause the buds to break!
The “Cold Winter” Model
The diagram below represents a plant after a fairly cold winter. The blue line at the bottom of the chart shows how much chilling this example plant received. The red vertical line shows how much “forcing” it requires to start growing. In this diagram, the winter has been fairly cold. Therefore very little forcing is needed to allow bud break.
The “Warm Winter” Model
This diagram represents what happens in a fairly warm winter. Once again, the blue line represents the amount of chilling a plant received, and the red line represents the amount of forcing the plant needs for bud break. By comparing the two diagrams, you can see that with less chilling, the plant needs more forcing to achieve bud break.
How is this relevant to the question, “Is this an early spring?”
The differences observed in my study may have come about in several ways. One attractive explanation is this: A “warm winter” easily satisfies the chilling needs of those plants with a low chilling requirement, but not those with a high chilling requirement. Once it starts to warm up in the late winter, the plants with a low chilling requirement would only need a small amount of forcing prior to bud break. Plants with high chilling requirements would not have had all the chilling they really “wanted” and thus would have needed extra-large amounts of forcing prior to bud break. Thus these plants would have delayed bud break and blooming.
So the real answer is that 2015 compared to 2014 was an early spring, a normal spring and a late spring, depending upon what plants you were watching.
Nature is always simple, but sometimes it hides that simplicity under layers and layers of seeming complexity. Much of science is dedicated to burrowing through the complexity to get to the simplicity. At one meeting for scientists Dr. John Gordon, former head of the Oregon State University Forestry School, welcomed us by saying,
“You’re coming here confused, and when you leave, you’ll still be confused, but you’ll be confused at a higher level.”
Sometimes that’s the most we can hope for!
The “Yucky Stuff” in the Creek
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
People come to Tryon Creek State Natural Area (TCSNA) to enjoy nature’s beauty. They want to enjoy a natural and pristine environment, largely unspoiled by humankind. Our free-flowing Tryon Creek is an object of particular attraction.
As beautiful as the creek can be, some visitors are alarmed when they see “pollution” (often referred to as “yucky stuff”) in the creek. The truth of the matter is, that what might look like “pollution” in the creek is oftentimes the result of purely natural processes, not pollution at all.
The two most common kinds of “yucky stuff” in the creek are white foam floating on the surface, and orange slime in the water. Once you understand these two kinds of “yucky stuff,” you can relax.
So what’s with the white foam?
Sometimes you can see large clumps of floating foam accumulate on the upstream side of logs or other barriers in the creek. A typical mass of foam, pictured below, spotted recently just upstream from Obie’s Bridge:
You might think it’s soapsuds that leaked into the creek, but it’s probably not human-made at all. What really happened is a longer, but more interesting story.
The edge of the creek is lined with all kinds of trees, especially red alder (Alnus rubra). Alders being alders, every fall dump huge numbers of leaves into the creek, as you can see in the photo below.
And leaves being leaves, they start to decay, oftentimes in the stream itself. The photo below shows a large clump of mostly alder leaves (now brown) that have sunk to the bottom of Tryon Creek. Numerous microorganisms are decomposing these leaves. Note the tiny clumps of white foam floating on the surface above these leaves.
So the leaves decay. Now what?
As microorganisms decay the leaves, DOC (dissolved organic carbon) is released into the water. DOC is a totally natural mesh-mash of different chemicals. One of the DOC chemicals is palmitic acid, which is shown below.
Palmitic acid is found in every red alder leaf. It is a major part of each cell’s membrane. Palmitic acid, or closely related chemicals, are found in every plant. Below is the chemical structure of a typical soap molecule manufactured by humans.
The resemblance is unmistakable. There are two more carbons in the soap, but the major difference is highlighted in red in the diagrams. It is easy to see how the palmitic acid might act a lot like soap.
Why do we get foam?
Normally, the water molecules at the surface strongly attract each other, and form what is basically a weak shield on top of the water. We call this shield “surface tension.” Small insects called water striders can be seen walking on this surface tension on top of the creek in the summer.
To see a demonstration of surface tension, please play the following video.
The DOC, just like soap, interferes with the natural bonding between water molecules in the surface tension layer. The end result of the soap or palmitic acid is that when air gets into the surface layers of the water, it isn’t squeezed out by the natural mutual attraction of the water molecules. Rather, the air enters the water and with a bit of agitation creates bubbly foam.
To demonstrate natural foam-making, I used a jar of Douglas-fir (Pseudotsuga menziesii) cones that had been sitting on my home office desk soaking in water for about two months. [Note: If you happen to see my wife at TCSNA, please casually mention that you also have a jar of Douglas-fir cones soaking on your home office desk. It will help me a lot!] I used this jar to demonstrate that you can create foam just from decaying vegetation. All you need is some agitation, like what you might get from “rapids” in the creek. Photos of this jar at various stages appear below. Note how much foam is floating on top of the water.
The foam persisted for a long time after the shaking. If this foam were produced in the creek, in 90 minutes it could travel a long way downstream.
So we’ve got white foam in the creek, what else?
The second type of “yucky stuff” we have in the creek is orange slime! This can be found in a couple of places at certain times of the year. I’ve seen some in the vicinity of Obie’s and Beaver Bridges. How this comes about is one of the most interesting and unexpected nature stories at TCSNA. The photo below shows a pool of orange slime in the creek.
Most of us have been told at one time or another that there are two types of organisms in the world. First there are those that use sunlight, water and carbon dioxide to produce sugar to provide energy for themselves. This is what salmonberries (Rubus spectabilis) and Douglas-fir trees do. They are called “autotrophs” from the Greek meaning “self- nourishing.” Second, there are organisms which eat and “burn” the carbon compounds produced by autotrophs to produce energy for themselves. These carbon compounds are as diverse as sugar and wood. This is how both banana slugs (Ariolimax columbianus) and people (Homo sapiens) survive. These organisms are called “heterotrophs,” from the Greek “other nourishing.”
Following this explanation, we see that the energy of the sun is the basis for all organisms. So far, so good, and if you are in 2nd grade, this is a decent way to start understanding life. However, the organism that makes the orange slime doesn’t fit into either of those categories. It’s weird!
I love weird stuff! Tell me more!
The weird organism is a special type of bacteria called “iron bacteria”. (I’ll skip lots of complex chemistry here! “You’re welcome!”) You and I eat carbohydrates like corn, donuts and potatoes, and oxidize it to get energy. In the process we give off carbon dioxide (each time we exhale) and water (through sweat, breath and urine).
Iron bacteria don’t do that. These bacteria “eat” a special iron compound (ferrous iron, if you must know). Ferrous iron is found underground where there is a deficiency of oxygen. As water carries it up towards the surface of the ground it encounters both more oxygen, and the iron bacteria. The iron bacteria oxidizes (“eats” to put it crudely) the ferrous iron, and “poops” regular old rust (ferric iron, for you geeks). These iron bacteria are classified as “chemoautotrophs” meaning roughly, “they feed themselves with chemicals.” That’s right, the orange slime you see in the creek is essentially rust excreted by these special bacteria. In eating this special iron, the bacteria get the energy they need to live. The photo below shows the ferric iron seeping out of the soil into the creek.
Given that TCSNA is just a few miles from an old iron mine, it’s not surprising that TCSNA’s soil contains the high levels of iron needed to support this kind of bacteria.
Unlike what you may have been led to believe many years ago, these bacteria represent a group of organisms which don’t rely on energy from the sun to stay alive. If the sun ever goes away, no more plants, no more bugs, no more birds, and no more people. Then the iron bacteria will have TCSNA all to themselves. It probably won’t be a very exciting place, but there will still be life here!
The next time you see some “yucky stuff” in the creek, pause for second before calling it pollution. You might just be seeing the end result of some very interesting natural processes. The floating white foam and orange slime are just as much a natural part of TCSNA as your favorite birds and flowers. They are another reminder that nature is endlessly fascinating.