Monthly Archives: May 2018
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
The forest at Tryon Creek State Natural Area (TCSNA) contains marvelous plants that we can enjoy at different seasons for different reasons. They range from the beautiful trillium (Trillium ovatum) blossoms in the early spring to the bright red leaves of the vine maple (Acer circinatum) in the fall. But these individual displays of beauty are transitory, as are the plants themselves. This is summed up in the Latin title of this note which means: “thus passes the glory of the world.”1
I started a phenology study in mid-2013. This involved, for the most part, identifying and tagging specific individual plants and monitoring their developmental stages each year. These stages were things like when I could first see the veins on the new leaves, and the first time I found open flowers on the plant. Now, just five years later, I am surprised at how many of those individual plants I was following have died in that short timeframe.
Plants are Persistent
As we realize, plants are persistent. In the photo below, you see the result of a very old injury to the trunk of a Douglas-fir (Pseudotsuga menziesii) growing at TCSNA. Long ago, the upright shoot of this tree was damaged or killed, and several side branches competed to take over the role of “leader.” The branches marked with red arrows lost the race to become leader and are now dead. The branch indicated by the blue arrow won, and became the leader so successfully, that it looks almost like it was always the leader. Several branches that were lower down the tree when the top was lost are marked with green arrows, and they remained horizontal.
Another example of a persistent plant is this mature black cottonwood (Populus trichocarpa) located alongside the Old Main Trail. Normally, mature black cottonwoods don’t have little branches popping out along the main trunk. However in this case, the reason can be seen in the wet dark seepage at the base of the tree. This tree appears to be infected with some microorganism (Fungus? Bacteria?) which is excreting a smelly fluid out of a crack in the tree. When Ranger Deb and I bored into the tree, the heartwood was definitely wet and smelly, evidence that it was decaying. In these cases, the tree doesn’t do such a good job of controlling the sprouting of the buds on the tree trunk.
Finally this Douglas-fir near Old Main Trail, which still has many green needles, sports numerous fungal fruiting bodies which indicate it is heavily decayed.
Plants are persistent, but…
Sometimes the trees have problems from which they never recover. The red alder (Alnus rubra) pictured below probably just aged out. Estimates of what constitutes “old age” for an alder varies from 60 years to a maximum of 100 years. Red alder is a species that likes full sun light and most frequently gets started on disturbed sites. So no surprise that we would find one this size dead.
A little more surprising is the dead western redcedar (Thuja plicata) pictured below.
This species is very shade tolerant, and under normal circumstances commonly lives several hundred years. So why is this relatively young tree dead? My best guess is based on the fact that this was found on the uphill side of the trail. Trails often serve as unintentional “dams” to the normal flow of underground water (great example: Old Main Trail near the Nature Center). A couple of years ago we had an extraordinarily rain-soaked winter season and I hypothesize that this cedar got “drowned out.” Yes, cedar frequently grows in wet-ish areas, but there is a limit to everything.
Individuals from several shrub species have recently died as well. This red elderberry (Sambucus racemosa) located just off the Old Main Trail (pictured below) is the plant that began my awareness of this topic and thus this whole article. This plant died before the recent winter with heavy rains. It was the first plant which was part of my multi-year phenology study that died. Additional walks around the park revealed many other dead elderberries. Again, it appears to be a fairly short-lived plant.
Perhaps the most dramatic die-off I’ve witnessed occurred near the upper section of the Red Fox Trail. Last year I noticed that many of the Indian plums (Oemleria cerasiformis) seemed to turn yellow and lose their leaves a little earlier than normal. This year, a relatively large number of them never leafed out. I laid out a 1/20 acre plot (a circle with a radius of 26.3 feet) and counted all of the Indian plum stems. I also measured their diameters at ground level. To the best of my ability, if I was able to determine that multiple stems were part of a single plant, I only measured the largest stem. Important confession: I chose an area with a very high density of dead stems. The results are summarized below:
In some cases these plants were quite large, both in height and diameter. I laid one of the stems on the sidewalk near the top of the Red Fox Trail to make it easy to see.
I selected a few of the larger Indian plums, and counted the annual rings at the base of the stem. They were between 15 and 19 years old.
As a final example, I’ve also noticed this year a number of dead salmonberry (Rubus spectabilis) in the forest. I don’t think this is the result of some climatic fluke or disease, because there are also a very large number of healthy salmonberries in every area where I’ve see a dead one. One example of a dead salmonberry is pictured below:
Below is a cross-section of stem from a dead salmonberry. Note the relatively large whitish pith in the center.
And let’s not forget the animals
Sometimes animals play important roles in the life of plants. A couple of years ago, beavers decided that a lot of the young cedar trees near Obie’s Bridge were ready to eat, and went in for the harvest. The results were evident by the number of chewed off stumps, like the one seen below.
“This too shall pass”2
The forest we see today is not the forest we will see tomorrow. Barring huge environment shifts, the major trend that we should expect is that much of our uplands forest will evolve to a predominantly redcedar-hemlock forest type. Douglas-firs will be relegated to a tiny role. Red alders may persist in some of the bottomlands near the creek. This of course will bring some shifts in the animals that inhabit our forest as well. It will be different, but still just as fascinating as it is today!
1Documentation on the web indicates this phrase was used as early as 1409 during the installation of the Pope.
2According to Wikipedia, this is an ancient Persian expression that worked its way into the English language sometime in the 1800s.