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First resurvey of the Lehigh Experimental Forest
Growth, mortality, and recruitment (shown in red) of dominant tree species in the Lehigh Experimental Forest from 2013-2015. Average tree size and numbers of indivduals included in the survey shown in blue.
Taking inventory of the forest, 2015.
Students in general ecology (EES-152) resurveyed a portion of the Lehigh Experimental Forest, to assess changes in tree growth, mortality, and recruitment since 2013. No new trees greater than 1.4 m high were documented, and both growth and mortality varied considerably among species. Over 500 trees were measured, and the plot above shows data for the dominant trees (those with >15 individuals included in the survey).
We will use these data as a springboard for discussion of processes controlling forest dynamics, and will examine some of these issues in greater depth during our discussions and future lab activities.
For now, students should answer the following questions:
1. The dbh measurements were converted into estimates of area, assuming that each tree was a perfect circle in cross-section. Why do you think basal area was used to compare growth among the different species? Why was this expressed as the average change in basal area per tree, as opposed to the total change in basal area for all individuals of the species? What factors might have caused the observed differences in radial growth among species?
2. What does the pattern of mortality and recruitment suggest about the future of the Lehigh Experimental Forest? What factors might have caused the differences in mortality among species during these two years? What factors might be contributing to the lack of new tree recruitment in the forest?
3. Which species had both very high mortality and very low growth during this time period? Do some research on current threats to this particular species, and summarize your research in a short paragraph.
Tweeting from the field: Natural history, trees, and a forest inventory
Students in ecology (EES-152) at Lehigh University share pictures of our field activities via Twitter. Below are some highlights from the first few field labs, which were focused on tree identification and forest inventory methods. The students resurvey experimental forest plots original established in 1915….
https://twitter.com/AMcCarter152/status/374234718025170944
https://twitter.com/SmallsKnowsAll/status/374978147097522176
https://twitter.com/SmallsKnowsAll/status/377122119173165056
https://twitter.com/neb215ees152/status/377604391957569538
https://twitter.com/sep214/status/378529415551918080
https://twitter.com/beagle757/status/379467160155742208
https://twitter.com/SmallsKnowsAll/status/379633937540079617
Trembley’s “tangled bank” on the Lehigh campus
Francis Trembley (1904-1978), pioneer ecologist, environmentalist, and professor of ecology at Lehigh University. In 1967, he convinced the administration to stop mowing the slope behind Williams Hall. The site was meant to be a place where students could observe secondary succession, right outside the classroom (Image from http://schoolintheclouds.blogspot.com/2012/11/nature-interpretation.html)
“It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. . .” – Charles Darwin
Where is the tangled bank?
Snippets of what little I could recall of the above quote from Charles Darwin bounced around my head as I read labels on some herbarium specimens.
Label of a herbarium specimen that was collected from Lehigh’s “Tangled Bank” in 1968.
My task was to reorganize this collection of carefully flattened and labeled dried plants, to make it more useful as a teaching resource.
According to the labels on these particular specimens, they were collected from the “Tangled Bank.” No other location information was given. Where was this place? What was its significance? The labels indicated that they were all collected by a person named David J. Mazsa. Maybe I could track this person down…
Finding David Mazsa
Google is amazing. Within a minute of searching, I found a person by the name of David Mazsa with a degree from Lehigh Unversity. Perhaps he was the collector? I sent him an email and received a prompt response….
“You are in luck- I am the guy you are looking for.
“Tangled Bank” is the sloped area right behind Williams Hall. Dr. Trembley had an idea to allow that mowed and manicured area to proceed through natural succession and become a “tangled bank” (I think the term is from Charles Darwin). Dr. Trembley convinced Lehigh to stop mowing and allow the area to begin to revert to it’s more natural state. In his view this would be so much more attractive and diverse than the mowed lawn. I honestly do not remember the exact chronology but my best guess is that they stopped mowing some time in 1967 and my samples were from the following year but I am not sure. Dr. Trembley found some money for me to work on the bank and take samples to record changes in the plant species distributions. I am amazed to learn that I left a mark! I graduated from Lehigh in 1969 and although I visited Dr. Trembley once or twice afterwards, I don’t know how long the project lasted or what additional data was collected.
Dr. Trembley was one of the people responsible for my career path. I was born and raised in Bethlehem and he wrote a lot in the local newspapers. He was one of the reasons I chose Lehigh. He was a combination of an old time naturalist who loved the diversity of living things and was eternally curious about how they interacted. Walking on a field trip with him was like having a window to the world of nature. We hung on his every word and loved his stories. But he was also politically astute and he was in the middle of Environmentalism of the 60s and 70s.
He taught Ecology with a set of note cards that were at least thirty years old. When we asked him if it was boring teaching the same stuff over and over again, he noted that the Ecology material was much the same, but the students changed every year and his interaction with them made it different every year. I have just finished my 40th year as a high school teacher and now I understand how right he was about the difference in students from year to year.
I also remember that our grade in Ecology was determined by a semester exam and that the question was “Describe life in, on, and around inland waters.” Although that was the only science course at Lehigh that I didn’t ace (I got a B I think), That course and Dr. Trembley are certainly one of the big reasons I have spent much of my life teaching and working toward making the world a more sustainable place.
I hope I helped identify the location for you. Thanks for bringing back some very fond memories.
David Mazsa”
So the “tangled bank” is the slope behind Williams Hall!
Of course! This is the only non-manicured place on the Asa Packer campus. And before the Department of Earth & Environmental Science moved from Williams Hall into the STEPS building, my office used to face it. For five years I looked directly out my window at the “tangled bank.” And I agree with Trembley, it is more beautiful and diverse than a mowed lawn. An aerial photograph from 1971 shows that much of the slope was still characterized by low-growing vegetation four-years after they stopped mowing.
The “tangled bank” on the slope behind Williams Hall in 1971 and today. In 1971, four years after the mowing stopped, low-growing vegetation on much of the slope is seen in the photograph. A few trees remained on the southern margin, which is the top of the slope.
After David’s email, I also found mention of the “Tangled Bank” in a book on the history of education at Lehigh University (Yates 1992, page 238):
“The biologist Fran Trembley was speaking and writing on the dangers of technology long before the subject became popular with the general public. In 1951 he had his title changed to professor of ecology. Students flocked to his classes. In order that they might have a nearby spot in which to study ecosystems, he asked that the slope above Williams Hall be left in a wild state – a tangled bank, he called it, using a term coined by Darwin. The administration complied with the request and put up a sign, “Tangle Bank,” to identify the place.”
The “tangled bank” behind Williams Hall. Trees are higher than the building today.
Today, the “tangled bank” is a small, diverse woodlot, with an overstory that includes tulip poplar (Liriodendron tulipifera), American beech (Fagus grandifolia), black cherry (Prunus serotina), several species of maples (Acer spp.), as well as several other deciduous species. Various shrub species occur throughout, particularly along the margins, and poison ivy (Toxicodendron radicans) and Virginia creeper (Parthenocissus quinquefolia) are common. It is a very different place than it was in 1968. A few more photographs are below (click on one to view as slides).
What can students learn from the tangled bank?
This fall, students in general ecology (EES-152) at Lehigh University, will revisit Trembley’s “tangled bank.” Forty-seven years of ecological succession have passed since the mowing was stopped, and because of David Mazsa’s collections we know many of the pioneer species that grew on slope after just one year.
Francis Trembley on the cover of the Lehigh Alumni Bulletin in 1970.
Students in the ecology class will complete a botanical inventory of the slope, and the data will be used to introduce and explore the topic of secondary succession. Furthermore, the students will use modern databases to research and compare information on the functional traits (e.g., seeds per plant, energy content per seed, growth habit, mode of dispersal) of plants in early succession versus mid-succession (i.e., today). We will report our results on this blog later in the fall semester!
Trembley’s last lesson.
Unfortunately, this will probably be the last lesson taught by Trembley’s “Tangled Bank.” A renovation of Williams Hall is planned to begin later this year, and as part of this effort the area will be relandscaped…removing the “tangle” from the bank.
Perhaps only this ecologist would be saddened by such a thing.
Looking for old trees on Lehigh’s campus
A beautiful spring day at Lehigh University, and many of the trees have sprung-out small leaves. I took a short walk on campus with Michelle Spicer to look for some old trees…and there are plenty of these on Lehigh’s campus. In fact, many of the larger oaks are well over 200 years old. However, we wanted to determine if a few particular trees mentioned in a 1934 article in the Brown & White, shown below, were still present.
A 1934 article from the Brown and White that discusses a few of the trees on the campus at that time (Vol. 42 no. 16). From the Brown and White archives.
The results….two out of three is not bad.
Photographs of an old white oak (>300 years) on the campus of Lehigh University. Note the gnarled base in the righthand image.
Gnarled old oak on the west-end of Christmas-Saucon Hall.
Yes, now over 300 years old (!), this old giant is still there and doing well. Although I have walked by this white oak (Quercus alba) hundreds of times, I didn’t really take much notice of it. You don’t realize how big it is until you approach it, and the size of its base is a bit concealed by its close proximity to the building.
“Old Man of the Mountain” wild cherry.
Unfortunately, this apparently charismatic and previously well-known tree is no longer around. Wonder when it came down?
An old tulip poplar (Liriodendron tulipifera) in the plot of land located at the corner of Brodhead and Packer on the campus of Lehigh University.
Ginkgo tree in the plot of land on the corner of Packer and Brodhead.
Yes, the Ginkgo (Ginkgo biloba) is still there and doing quite well. This area of campus is also one of my favorites, a wonderful park of many large trees – sugar maple, tulip poplar, norway spruce, oaks, and even a Kentucky coffeetree. Many of the trees in this area still have labels (labels are on some trees throughout campus, but quite a few have fallen off).
The plot of land on the corner of Brodhead and Packer – one of the many arbo-gems of the Lehigh University campus.
Addendum, 27 August 2013
Students in EES-152 (Ecology) at Lehigh University were given the 1934 article as part of an introduction to tree identification. They managed to find both the “gnarled oak” and the Ginkgo. Some of the best pictures are below…
The Ginkgo
https://twitter.com/beagle757/status/372134419639042048
The “gnarled oak”
https://twitter.com/SmallsKnowsAll/status/372101278932819968
Among The Stately Trees 