What's a tropical dry forest?

           

Before coming to Costa Rica, I imagined it to be a land full of the famous red-eyed tree frogs and the lovable sloths. I imagined trekking through the depths of the jungle with a machete in hand and binoculars in the other. I imagined packing my hiking backpack and going on onerous hikes. In my head, the entire country was essentially one giant rainforest. I knew that the capital, San Jose, was a bustling city, but I assumed that it was completely surrounded by forests.

            I soon found out that I could not have been farther from the truth. In the country the size of South Carolina, there are twelve different life zones according to the Holdridge Life Zones (a system used to classify different regions based on variations in temperature and precipitation) which accounts for numerous ecosystems. Of course Costa Rica has tropical rainforests, but it also has low-, mid-, and high-elevation ecosystems that all have their distinct characteristics. During the OTS course, I was utterly shocked to find out about ecosystems that I did not even know existed. Every year since second grade, there has always been a small section in my science classes dedicated to different ecosystems. I learned about the six typical biomes: rainforests, savannahs, deserts, temperate forests, grasslands, and tundra, but I had never once heard about the tropical dry forest. I thought Costa Rica’s tropical dry forests sounded like a misnomer – how could there be a “dry” ecosystem in an area of the world where rainfall is typically the highest?

            Now, not only have I learned about tropical dry forests, but I have actually seen one in person. This is super exciting for me because they are among the most endangered ecosystems in the world -- less than 1% of it remains and less than 0.1% of it is conserved. The dry forest here at Palo Verde National Park is characterized by its two seasons. We are currently at the end of the rainy season which occurs from late May until late November. The grasses outside are still green, and the trees have all their leaves. In the upcoming weeks, the dry season will start. During this period many of the plants drop their leaves, and everything turns brown. In general, dry forests also tend to have a lower canopy than their tropical rainforests counterparts, and the plants are equipped with an array of spines, thorns, and prickles. Because of the lack of consistent rain, tropical dry forests also do not tend to have as much biodiversity as a tropical rainforest; however, they still have some amazing animals.

            While studying at Palo Verde, there has been a weird disconnect between seeing rabbits and white-tailed deer and hearing the howler monkeys off in the distance. For a split second I think I am back home in Tennessee as I walk around the deciduous tree forests and see the stereotypical forest dwelling creatures, but the reality sets in that I am still in Costa Rica when I look up and see howler monkeys and white faced capuchins resting in the trees, or I see large iguanas on my way to the trails. I walk through the forest that looks similar to home but sounds nothing alike as I listen to the scarlet macaw calling from above.  It never occurred to me that it is possible that all these different animals could live together in unison. As much as I love the wildlife back home, I am going to miss some of the fauna I’ve seen here. 

Kiersten Bell

Duke University

All I have to ~ bee ~ thankful for

           

Lame puns aside, OTS has provided me an amazing outlet to which I could experience another field of science. Our final site was at the Palo Verde National Park. The climate, marsh, and mosquitos were very reminiscent of back home and that was comforting when trying to finish the last stretch of the semester. One part of this ‘stretch’ was the second independent project. I worked with Jocelyn on the effect of florivory on bee behavior and interactions with plants. This project was a complete 180 from my La Selva project because instead of working till 2am, we were starting at 5:15 am. I thought the idea behind the project was super interesting and once we analyzed the results I thought the implications were also very interesting. What I had a hard time convincing myself of was staying motivated to do the project each morning. I am, definitively, not a morning person. This is especially true when I have to walk through the marsh to pick 120 water hyacinth inflorescences, cut their flowers, and make the plots stay from falling over into the water at 5:30 in the morning. Once the plots were made, we sat in the direct sun for 3 hours counting the number of times bees landed or hovered over a flower. The project, in all honesty, was very monotonous. With all this being said, I am extremely glad that I did the project. I had never had the experience of doing this type of fieldwork and it was quite different than I had expected. Whether or not I found this project to be the most exciting thing on earth or not, I learned from it and I grew because of it and that’s what I was looking to get out of my OTS experience. 

            On one of the days that we had free, I took a walk through the dry forest to reflect on the program and have some alone time. I didn’t know where I was walking to and didn’t particularly care. While heading down a main road of the park, I saw a trail called the ‘mirardor’ trail and figured that if I was going to be spending a couple weeks here I might as well look at the park at a lookout site. The trial wasn’t kept up as indicated by the fallen trees over the path and the apparent lack of visitation. After about an hour or so I came across a small pile of limestone rocks. As I kept forward, I saw that the rocks got larger and larger until I saw them go to the top of the side of the mountain. The path had just stopped so I decided that it would be a fun idea to scale the side to get a better look at everything. Climbing up the rocks, getting cut by Agave seemanniana, and avoiding cacti made the end of the walk a little more difficult than the mosquitos had already made it. Once I got to the top, I sat on the edge of a rock and looked out over all the dry forest. The view was beautiful and the gentle breeze made the rest comforting.

            While looking out I came to realize a few things from this trip. My first was that I am so lucky to have been given this opportunity to join this program. Being a low-income first generation student, I had never imagined being able to go to Duke, let alone live in Costa Rica for four months. Traveling from Las Cruces to Palo Verde and everywhere in-between has been an unforgettable experience. My second was that to an extent, I really enjoyed doing fieldwork. I loved being able to collect samples from the natural environment and perform experiments with them. While this might not make its way full time into my future endeavors, I want to incorporate to some degree an aspect of fieldwork. Collecting my own samples from nature helped put a lot things into perspective for me. Lastly, I realized that this trip is going to stay with me for the rest of my life. The experiences, friends and knowledge that I gained during this study abroad are one of a kind and I’m very happy in my choice to join OTS. 

Tanner Waters

Duke University

Our last project: a retrospective look at the course

Palo Verde is our last field station, and marks the end of our course in Costa Rica. As always, the days are packed - within a week we had finished two faculty-led projects and begun our final independent projects.

My friend and I worked on a fun little aquatic plant called Neptunia natans. It is seismonastic (the leaflets fold into themselves when touched or blown on) as well as nyctinastic (the leaflets close at night). This movement occurs remarkably quickly and is thought to be a response against predation. We decided very quickly that we would like to work on this behaviour.

In order to formulate a question we spent a few hours snooping around the marsh. We noticed that the walkway extending into the marsh seemed to create a constantly shaded habitat for the Neptunia. This meant that there were two different light habitats for the plants: one shaded (under the boardwalk) the rest were lit (exposed to the sun). Organisms adapt to their constantly changing habitats using plastic adaptations that allow them to maximize resource gathering. This phenomenon is known as phenotypic plasticity. We decided to ask whether our plants had plastic adaptations and whether these affected their willingness to take risks in terms of seismonastic behaviour.

            We then set to work. Our first task was to collect plants from the marsh, which involved wading through thick vegetation and dodging the throngs of ants that crawled over the stems of the water lilies, Once we collected shade and sun plants we whisked them off to the lab, where we measured how much they closed and how long they took to open when tapped with a pencil. We also timed their nyctinastic behaviour to see whether sun plants and shade plants showed any differences in circadian rhythm.

            Four days later, we had a dataset to analyze. The results of our small experiment surprised me: the two types of plants showed clear differences in circadian rhythm and response to threat despite growing less than two meters apart from each other in the same stream. The boardwalk had created plants that looked and behaved completely differently to their neighbors in the marsh.

            Throughout the course we have encountered many examples of the dizzying complexity of biotic and abiotic interactions. To me, the behavioural complexity of a simple water plant highlighted this characteristic of tropical forests. 

Avehi Singh

Reed College