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.
The Pymatuning wetlanders demonstrated their knowledge of wetland ecosystems this morning on the final exam.
The end of this course is always a bit bittersweet for me. Teaching a field course like this is intense, high-energy, all-consuming, and by the end…. exhausting. However, without a doubt the experience has once again been the highlight of my professional activities for the year. Each time I teach this class, I get to learn something new about wetland ecosystems and sharpen my natural history and plant identification skills. I have the opportunity to get to know a bunch of interesting students, much better than I would in a typical classroom setting. And it is extremely satisfying to share my knowledge and passion for natural ecosystems with a group of interested students. The Pymatuning Laboratory of Ecology is an ideal place to do this.
Field courses are transformative experiences. For me, it was a fantastic course in field botany nearly 20 years ago. We were in the field every day, collecting plants and learning about their biology, evolution, distribution, and natural history. I was amazed at the depth of knowledge of the professor, and his passion for plants was contagious. I knew that I wanted to do science before that course, but after it I knew that I wanted to be an ecologist. Sadly, while teaching here at Pymatuning this year I found out that the instructor of that field botany course passed away in late May. Professor Don Drapalik, RIP. He was on my mind a lot during the past few weeks, particularly as I watched the students build their wetland plant collections. I still have my plant collection from Don Drapalik’s field botany course, and I am pleased that a large percentage of students this year want to keep their collections.
I sincerely wish the best for this great group of “wetlanders.” It was a really fun-loving group, and there was lots of good-natured humor along with the learning. I wish them all good luck with wherever life takes them from here.
Keep in touch….and stay peaty. #PLEwetlands
The Pymatuning Wetlanders visited Presque Isle today, where we observed coastal processes and successional change. After a stop at the Tom Ridge Environmental Center, explored the peninsula to observe coastal wetlands and processes. This included a hike out to Gull point, located at the tip of the peninsula, to observe the youngest landscape and wetlands. We did some wading in Lake Erie to cool off, had lunch on the beach, on our way home we stopped for the long-promised ice cream. A fun day before tomorrow’s final exam.
The Pymatuning wetlanders learned about the role of wetlands in the broader earth system this morning, with a focus on biogeochemical cycles and climate change. This was followed by a quick overview of federal laws that protect wetlands, particularly the history and controversy surrounding the Clean Water Act.
We headed to Hartstown Swamp in the late morning, where the students were tasked with conducting an actual wetland delineation along a transect from the swamp to the upland. They received little to no help from me, and had to self organize, determine what data to collect, and then carry it out. They did a fantastic job, and integrating and applying their knowledge of wetland plants and soils. They have come a long way; in fact, just a couple weeks ago most of them struggled to provide a definition for the term “wetland.” Their data from along the transect was used to construct the diagram below, and we will discuss these results in the morning.
Today the Pymatuning wetlands spent the entire day in the lab. Our first day without any fieldwork since the course began. However, we made up for it by doing a bit of time travel…
We examined the core we collected from Titus Bog yesterday. We subsampled the sediment and peat, sieved the samples to isolate plant macrofossils (i.e., seeds, leaves, needles, etc.), and identified and tallied the microfossils to determine how the vegetation of the wetland has changed over the past 8000 or 9000 years. The students determined that the site was occupied by a shallow lake prior to the establishment of the modern peatland, with submerged and floating leaved aquatic plants like Najas (water nymph), Nuphar (spatterdock), and Nymphaea (water lily) growing in the deeper portions of the littoral zone. Emergents like Cladium (sawgrass), Rhynchospora (beaked sedge), and other sedges likely occupied the lake margin along with small amounts of Sphagnum moss. The area abruptly became a floating peatland about 350 years ago, when Sphagnum became dominant. The upland vegetation around the site contained Tsuga canadensis (hemlock), Pinus strobus (white pine), and Betula alleghaniensis (yellow birch) for much of the record. Most of the species in the paleoecological record have been observed at the wetlands we have visited during the past two weeks of the course; in fact, quite a few are the “must-know” list.
Our age estimates for the record are tentative and come from a broader study of peatland development at the site by Ireland and Booth (2011). We will discuss our paleoecological record in class tomorrow, along with the Ireland and Booth study, emphasizing the implications for understanding long-term wetland development and hydroseral succession.