On July 30th 1935, Francis Trembley walked along the north-facing slope of South Mountain above the campus of Lehigh University. Dr. Trembley was a biology professor, and he stopped along the road to collect some goldenrod and several other herbaceous plants that were in flower at this time. He then likely entered a semi-open area on the southern side of the road that was carefully planted with clusters of different tree species. There, in a plot of land only about 11 acres in size, he probably observed over 90 of the tree species native to Pennsylvania, and as many as 200 types of North American trees (Emery 1915, Hall 1951). At least 20 species of oaks were represented alongside maples, pines, basswood, beech, yellow buckeye, tulip poplar, red spruce, and many others (Hall 1951). This museum of trees resulted from the foresight and passion of another Lehigh biology professor, Robert Hall. Dr. Hall was instrumental in acquiring the land for the university in 1908, and he designed and oversaw the plantings, which were apparently positioned on the property to broadly reflect botanical relationships (Hall 1951). This “informal park,” as Hall envisioned it, was the Lehigh University Arboretum. By all accounts, it was one of the finest university arboretums in the country.
On that day in July, Trembley probably also walked a bit further east past the arboretum, where he would have observed a young, wedge-shaped forest that was meticulously divided into a series of 42 experimental plots. Initially established and planted in 1915, the plots included over 20 tree species native to North America and Europe. Some plots were planted with a single species and others a mixture of two species. This was the Lehigh University Forest Plantation. Set up as a forestry experiment to assess what economically valuable species would grow best on the rocky, thin soils of South Mountain and similar areas in Pennsylvania, the value of the experiment was highlighted by the President and Vice-President of the University, Henry Drinker and Nat Emery, at a speech to the Pennsylvania Forestry Association in 1915. However, by the end of the 20th century both the arboretum and the forest plantation would be almost completely forgotten…engulfed by the surrounding forest.
How do we know that Trembley went up to the arboretum on that day in 1935? The plants that he collected on the edge of the arboretum are archived in the Lehigh University Herbarium. In fact, the discovery of the herbarium specimens is what first sparked our interest in relocating the arboretum.
The History of the Arboretum
In 1951, Robert Hall finished a manuscript entitled “History of the Lehigh University Arboretum,” and although he clearly doubted that it would have much use to anyone, he filed it away in the University library. The document contains much of what we know about the arboretum – how and why it was established, the role of the adjacent nursery and seedbeds, the adjacent forest plantation, and the many challenges he had to overcome. It might sound like dull reading, but it isn’t. In fact, the second half is a bit of a political thriller. Well, perhaps not a thriller, but it does provide a fascinating window into university politics of the early 1900s. Other sources of information on the arboretum include a brief statement in the 1910 yearbook regarding the purchase of the land, various articles in the student newspaper (The Brown and White) which mention or describe the arboretum, and two publications in the journal “Forest Leaves,” which was published by the Pennsylvania Forestry Association.
Archives of the student newspaper reveal that the arboretum played practical, educational, and cultural roles for the university and students until sometime in the 1950s. For example, the arboretum and associated nursery provided replacement trees after the American chestnut blight eliminated the chestnut trees on the main area of campus (Brown & White, March 10, 1916) and it was a continual source of trees for the rest of campus in the 1920s and 1930s. Students and faculty also went to the arboretum and forest plantation to learn, observe, admire, and even have a little fun. Francis Trembley used the arboretum for his classes. An open-air theater within the arboretum, referred to as Top ‘o The Mountain theater, was used for plays during the summer session in the 1930s (Brown and White, Sept 26, 1936). And for fun, mischievous Lehigh students occasionally swapped the labels on the trees (Brown & White, Oct 6, 1943). Lehigh students were apparently just as wild and crazy then as they are today!
The last mention of the arboretum in the student paper was an anecdotal mention in 1954, and Robert Hall seems to have recognized the declining interest in the arboretum in his 1951 manuscript:
“The last time I saw it, the arboretum looked like a monument to neglect – grass uncut, limbs stretching out over the road. It had seemingly been years since any car had tried the road.”
“What is the condition of the arboretum today? I do not know. If I were not seventy-nine years old I would climb up there and see.” – R.W. Hall
When Hall wrote those words in 1951, a new forest was likely already sprouting within the spaces between the carefully planted trees. Priorities change. Human memories fade. There were no more plays at Top ‘o The Mountain Theater. The students stopped moving the tree labels. The arboretum disappeared from campus maps.
Rediscovering the trees
The arboretum and forest plantation were relocated in the fall of 2011, and the story of this rediscovery was recently told in the Lehigh Alumni Bulletin (see here). Luckily for us, both the arboretum and the plantation land are still forested and have not been extensively disturbed by development. These areas of campus, and the trees that are on them, provide a potentially rewarding scientific opportunity to better understanding the legacy of a planting and reforestation experiment. Furthermore, they represent an opportunity for the Lehigh community to reconnect with the history of the university and explore our changing values and priorities.
The Lehigh Experimental Forest Plantation
The forest plantation was less commonly mentioned in the student newspaper, although the archives reveal that it was occasionally mistaken to be just another name for the arboretum. Given that its mission was scientific, it is not surprising that it received less attention. Although two articles on the experimental forest plantation were published, it appears that it was forgotten about quickly.
Henry Drinker elicited the help of others in the establishment of the forest plantation. Joseph Rothrock, the first president of the Pennsylvania Forestry Association, and Simon Elliott of the Forestry Reservation Commission, were called on to assist in its design (Emery 1915). Seedlings, all the same age and less than about six inches tall, were densely planted in the plots in 1915. It was meant to be a natural experiment with little to no intervention after the the initial planting, and it appears that no additional management was performed. In fact, Rothrock assessed the experiment after 5 years and noted that several tree species had already established naturally (i.e. without planting) within the plots, including black birch (Betula lenta), black oak (Quercus velutina), and black cherry (Prunus serotina). The latter two species were also planted in several plots. The total number of each species that were planted was as follows:
- 600 Basswood (Tilia americana)
- 300 Black cherry (Prunus serotina)
- 300 Black oak (Quercus velutina)
- 400 Bur oak (Quercus macrocarpa)
- 100 Elm (Ulmus americana)
- 400 European larch (Larix europa)
- 100 Grey birch (Betula populifolia)*
- 100 Hemlock (Tsuga canadensis)
- 300 Honey locust (Gleditsia triacanthos)
- 500 Jack pine (Pinus banksiana)
- 500 Norway spruce (Picea abies)
- 100 Pin oak (Quercus palustris)
- 500 Pitch pine (Pinus rigida)
- 100 Red spruce (Picea rubens)
- 400 Scotch pine (Pinus sylvestris)
- 400 Sugar maple (Acer saccharum)
- 600 Tulip poplar (Liriodendron tulipifera)
- 400 Western yellow pine (Pinus ponderosa)
- 700 White ash (Fraxinus americana)
- 300 White oak (Quercus alba)
- 500 White pine (Pinus strobus)
Like most science of the time, Rothrock’s assessment of the forest plantation after five years of growth was very qualitative. He attempted to summarize both the relative height and general health of the planted species. He noted that 1919 was a locust year (he was likely referring to cicadas), and that the hardwoods, particularly the oaks, suffered extensive damage. Although cicadas are not usually a problem for adult trees, their egg laying can damage small trees. He also noted that several species were damaged by fire, which apparently was common at the time on South Mountain (Rothrock 1920). In fact, the arboretum had a fire break around its perimeter (Hall 1951).
Although Rothrock’s assessment was qualitative it still provides a nice picture of the changes that occurred in those first few years. Some clear winners and losers were emerging by this time. In general, conifers initially did better than the hardwoods. Hemlock, elm, and honey locust all perished quickly. Tulip poplar, basswood, white oak, and ponderosa pine were all alive but not faring well, as several of these species were hit hard by cicadas and/or fire. A number of species were moderately successful, including sugar maple, white ash, and white pine; however, the tallest growing and healthiest trees were the european larches, scotch pines, and jack pines. Black birch, which wasn’t planted but colonized the site naturally, and black cherry were also doing quite well after five years. Although much slower growing, the spruces were thriving. Of course, Rothrock recognized that his report only captured a small piece of a long-term experiment – an experiment that would continue to play out for decades to come:
This experimental tree plantation was the beginning of a practical scientific experiment, so far unique in this country, which is bound in ten, twenty and fifty years to be productive of information of great value to the forestry interests of Pennsylvania and of the country at large. – J.T. Rothrock
A century of change
Fast forward nearly 100 years. What happened? Did Rothrock’s initial observations forecast what the forest would look like today? How many of the planted species survived? How did natural ecological succession play out against this backdrop of plantings? How did plant and animal invasions of the past century impact this unusual forest? Were some plots more susceptible to invasion than others? If Rothrock, Elliott, Drinker, or Hall had had the ecological knowledge of today, could they have predicted what the area would look like in 2012? How do other ecosystem characteristics and processes (e.g., soil characteristics) vary in the different plots today? What other legacies of the plantings exist? Given knowledge of the past, present-day patterns, and forecasts of the future, what might this forest look like in another 100 years? Students at Lehigh University are now investigating these and other questions, using this unique experiment as a natural laboratory. Stay tuned for the results.
The Epitome, Lehigh University Yearbook, 1935. Download here.
The Epitome, Lehigh University Yearbook, 1910. Download here.
All Brown and White articles mentioning the arboretum can be downloaded here.
Hall, R.W. 1951 (1945-51). History of the Lehigh Arboretum. Download here.
Emery, N.M. 1915. A demonstration tree plantation at Lehigh University. Forest Leaves 15: 56-58. Download here.
Rothrock, J.T. 1920. The demonstration tree plantation at Lehigh University. Forest Leaves 18: 9-13. Download here.