Lots of fun was had in EES-152 (Ecology) at Lehigh University this fall. Below is the annual student tweet roundup…..
Some of my favorite course-related tweets in Fall 2017…. another semester of fun!
It is starting to feel like fall, although there are not many colors in the trees yet.
The colors were vivid on the day pictured in the painting below, and I fondly remember a really great hike through a hemlock-dominated ravine as part of this camping trip a few years ago. The painting was an attempt to capture a moment that I spent watching my daughter as she sketched in her notebook.
General ecology (EES-152) students have finished resurveying a portion of the Lehigh Experimental Forest, assessing changes in species mortality and recruitment since 2013. A total of 1174 trees were inventoried and measured from across the forest the last two years, representing more than 1/2 of all trees originally tagged in 2013. In the four years since 2013, 167 of these 1174 trees have died (~14%) and only eleven new trees have established in the study area (<1%). Data for the dominant tree species are shown in the plot below.
We will use these data to discuss processes controlling forest dynamics as the semester progresses. However, for now, students should answer the following questions:
- What factors might have caused the differences in mortality among species?
- Develop a hypothesis to explain the lack of recruitment for most tree/shrub species. Then do some research on the two tree species that have successfully recruited and those species that have not. Are there species traits that are common to successful and unsuccessful recruiters? Are these traits consistent (or inconsistent) with what you might predict from your hypothesis?
- What does the pattern of mortality and recruitment suggest about the future of the Lehigh Experimental Forest? Assuming the rates of total tree recruitment and mortality are representative of future years, when will there be less than 100 trees in this forest? In 2013, there were ~2000 trees in the forest so you can use that as your starting number. Show your work and describe how you arrived at your estimate. Do you think this scenario is likely? Why or why not?
Last September, two invasive aquatic plants, water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes), were discovered in the Lehigh Canal in Bethlehem PA. Both species are floating plants, like duckweeds but much larger, and they often grow in dense mats in tropical and subtropical regions. Although this was the first confirmed occurrence in natural habitat within Pennsylvania, both species are sensitive to freezing temperatures so they have not not been regarded as major threats in the Northeast. A description of the discovery of these populations and some background on the species, including a discussion of recent work suggesting that the overwintering potential may be greater than previously thought, can be found in my post from last year (New invaders in the Lehigh Valley? Or Just Summer Visitors?).
The discovery last year prompted several questions. In particular, are these populations really persisting from year-to-year and therefore surviving freezing temperatures? I suspected that they were introduced last summer from someone’s pond and that they would not survive the winter. However, the winter was mild and the recent discovery of some overwintering populations in the lower Great Lakes gave me pause. I road my bike along the canal towpath last week to have a look.
I was wrong. Both species have overwintered. A harbinger of things to come? Below are some pictures, and I’ll update this post with more later in the summer.
20 Jan 2017
Today, we were accompanied by Felipe Velasco again, although this time instead of driving south toward Lake Tota we headed northeast toward the town of Mongua. We are extremely grateful for the time that Felipe has devoted to our efforts, as we would have had a difficult time finding these sites without him and it was reassuring to have a local person along. Our goal today was to explore and hopefully collect a core from Laguna Negra, a lake located in a different sort of paramo ecosystem. The drive was quite different than previous days, because we were able to see a much more industrial area of Boyaca. Between the cement factories and the steel mill, the pollution levels were quite high; in fact, much of the drive to Mongua smelled of a fragrant mixture of burning coal and diesel, and when we ascended the mountain above Mongua we observed a thick layer of smog in the valley. However, it was fascinating to see a fully functional steel mill, as gave me an appreciation of what Bethlehem Steel in Pennsylvania must have been like when it was operational. We observed many small family-owned coal mines along the road near Mongua, as this is the primary economic activity in this region.
Laguna Negra and the surrounding landscape was spectacular, and pictures really can’t convey the natural beauty of this place. While Jason and Jaime took measurements of the depth profile of the lake, I had the opportunity to hike around the lake margin. Unlike other lakes that we have visited, the lake margin was not peatland. Hypericum (St. John’s Wort) was common along the lake edge, along with a number of Carex species, and bright red Azolla grew in the littoral zone along with submerged aquatic plants like Myriophyllum. Inflow into the lake comes in the form of a spectacular waterfall, with abundant mosses and ferns growing adjacent to the waterfall in the perpetually humid environment.
The lake was about 9 meters deep with at least 3 meters of sediment, so we inflated a second boat, set our anchors, and commenced sediment coring. Mark Brenner and Felipe Velasco observed from shore, taking pictures of the coring process. We obtained several meters of mud, and once again we carefully kept the upper drive containing the mud-water interface upright on the trip back to Finca SanPedro.
On our way home we stopped in Mongua for some delicious empanadas and then went further down the road to Tópaga to take a look at the church on the main square. The Tópaga church is over 400 years old, and the inside is ornately decorated in gold. Colombia has abundant gold; in fact the yellow in the Colombian flag symbolizes the tremendous gold resources. This church in Tópaga is also probably one of the few churches that not only has artwork incorporating Jesus, the disciples, and other typical biblical representations, but also the devil. Yes, Lucifer himself is on a beam in the ceiling near the front of the church, directly center.
Our fieldwork is now complete. Tomorrow we will ship samples and cores from Sogamoso and then drive down to Bogota to pick up samples from our work in Manizales and prepare to depart on Sunday. This trip has been an amazing experience, and I feel extremely lucky to have had the opportunity to explore this fascinating country and see its amazing natural beauty. I am excited about this new collaboration, and the potential to develop long-term perspectives on water availability and ecology of the critically important paramo regions.
I sincerely thank Jaime Escobar for making this all happen. And I especially thank him for the doing all the driving!
18 January 2017
We traveled back up to Aquitania Lake today, managing to navigate back to it without the help of Felipe. We spent the day successfully collecting the full sediment record from the lake, over 7 meters of mud. While Mark, Jason, and Jaime did the coring, I collected plenty of surface samples from the surrounding peatland. Part way through the coring, we had a Colombian visitor who came to the lake on his horse to ask us what we were up to. He seemed amused by our activities. Not wanting to strap all the PVC and wood back onto the car, we offered it to him. He was thrilled to take it, and we gave him rope so that he could strap it all together and then tie it to his horse. I was really impressed with his rope tying ability, and although the horse did not seem particularly happy about the situation, it carried all the pipe and wood away.
Anyone know what kind of bird is in the video below? A sandpiper of some sort?
A collage of some of the interesting plants observed around the margin of the lake:
After a quick dinner in Sogamoso, we returned to Finca SanPedro where Mark Brenner gave a public talk highlighting the paleoclimate work that he has conducted with Jaime, Jason, and others in Latin America. Impressively, Mark gave the talk in both English and Spanish! I’m really going to have to learn some Spanish before my next trip to Colombia.
17 Jan 2017
It was dark when we arrived last night, so we didn’t have a chance to really see the beautiful Finca SanPedro Hostel. The house has a number of nice rooms for guests and the grounds were beautifully planted and maintained. Chickens, peacocks, vegetable gardens, a yoga studio, and four friendly dogs all added to the charm.
Felipe Velasco, director of the Foundation Montecito, graciously agreed to take us to a small lake in the paramo above Lake Tota. Our goal was to assess the potential of the lake for sediment coring, and potentially collect more surface samples from the associated wetlands. However, before embarking on our trip we needed to purchase a few more supplies from a local hardware store in Sogamoso, including some PVC pipe and some wooden boards to secure our inflatable boats together for a coring platform. The folks at the hardware store were fantastic, providing supplies and assistance as we mounted the pipe and boards on top of our car. Furthermore, about half way through the process, they provided us with free coffee and delicious empanadas. And they gave us free hats and windbreakers with their logo! As Jason commented, “it is strange that the best empanadas I’ve had were from a hardware store.”
The drive to the paramo took about an hour and half, but along the way we got see Lake Tota and the town of Aquitania. Lake Tota is the largest natural lake in Colombia and lies at an elevation of about 10,000 feet. As we crossed into the lake’s watershed, we were immediately hit by the smell of onions. Most of the area around the lake and the surrounding hillslope is covered in onions; in fact, according to Felipe, the area produces more than 90% of the onions consumed in Colombia. The lake is also used for fish aquaculture, and along with fertilizer runoff from the onion farms, environmental degradation of the lake is of considerable concern. Apparently for every ton of chicken poop that comes in by truck, a ton of onions goes out.
Furthermore, the introduction of rainbow trout into Lake Tota likely led to considerable changes in food-web structure, and the extinction of a species of catfish, known as greasefish (Rhizosomichthys totae) that was endemic to the lake. An all to common story: invasive species + human impacts like eutrophication = extinction.
The town of Aquitania borders the lake, and we had to weave our way through it to reach a steep dirt road that led up into the paramo. A small town with obvious economic hardship, the central square of Aquitania is dominated by the church like in many of the small Colombian towns that we have seen. On top of the church is a large statue of Jesus standing on a boat, although because the boat is small it looks like Jesus is surfing. The road up into the paramo was in bad shape so we went slow, but we eventually arrived at the small lake that we hoped to reach.
Lake Aquitania, as we called it, was beautiful. Surrounded by paramo, including lots of frailejón (Espeletia sp.), the lake is bordered by extensive wetland in places. Several nearby depressions also contain wetlands. After inflating a boat, Jason and Jaime used a sonar depth finder to quickly determine the depth of the lake. Although the lake is relatively shallow throughout (~40 cm), there was over 7 meters of sediment! Mark, Jaime, and Jason spent a few hours collecting a surface core to carefully capture the mud-water interface, and I spent the time collecting surface samples from the adjacent wetlands. We then returned back to Sogamoso while Mark held the core upright, partially sticking out of the car window, and upon returning we extruded the core centimeter by centimeter into bags. Tomorrow we will return to collect the full sediment core, as well as additional surface samples from wetlands surrounding the lake.