Travel: Day 4 - Puerto Rico - Dry forests and ancient trees

One of the advantages of teaching at a small liberal arts institution is the freedom to design and offer courses that are close to your heart. In January 2011, I was fortunate enough to lead a group of 6 students through the world of Tropical Ecology. Apart from not being in the right ecosystem, Nebraska in the winter is definitely not the place to have field trips about Tropical Ecology. Consequently, one portion of the course involved a 10-day trip to Puerto Rico where we got to see for ourselves all the things we talked about in the classroom.

This is a travelogue of our adventures together, the sights we saw, the things we did, and the lessons we learned.

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Day 4 and Day 5 marked the birthdays of two of the members of the group. What are the odds that in a 10-day trip taken by 7 folks, two of them would celebrate a birthday in that period? After the obligatory midnight birthday ritual, we went to sleep knowing that Day 4 would be one filled with with a lot of walking and talking, sometimes both together. AJ finally had company under the stars, with MB joining him after the midnight party.

(C.S. Manish 2011)

Dr. Skip v B of the University of Puerto Rico (Mayaguez) was our guide for the day. After general introductions, we bundled into two vans and drove to the dry forest in Guánica, or to give you it's official name: Bosque Estatal de Guánica.

(C.S. Manish 2011)

Located in the driest part of Puerto Rico, the dry forest extends from a scrub forest near the sea to an upland deciduous forest. Astonishingly, for a place considered to be too dry for most species to survive in, the dry forest has more species of birds than the tropical rain forest on the other end of the island because of less competition for food from lizards and insects. It is the only place in the world where the the Puerto Rican crusted toad, an endangered species, can be found in its natural habitat.

(Sami Wysocki 2011)

As you would expect with any dry area there are plenty of cacti, specifically the Sebucán (Pilosocereus royenii) within the forest. However, in the past few years there has been a severe infestation of the cactus by the Harrisia cacti mealybug (Hypogeoccocus pungens). The mealybug likes to feed on the apical meristem tissue. Mealybug infestation results in the formation of a new shoot as a defensive response. The new shoots, which look like tumors on the cacti, are also soon devoured by the mealybug, eventually causing the cacti to die.

(Andrew Jacobsen 2011)

Tropical soils are typically quite acidic (pH of around around 4) but the Guánica Forest is unique in that the pH of the soil is alkaline (a little over 8). The reason is that the calcium carbonate in the rocks binds to phosphate making orthophosphate which is unavailable to the plants, increasing the pH. The reason why calcium carbonate is found in large quantities in the soil has to do with the origin of the land that the forest rests on. A long time ago it was the bottom of the sea and tectonic uplifting eventually raised it above the sea level. A combination of water and wind erosion has left behind what we see today.

(Katie McKenna 2011)

Most of the trees in Puerto Rico were harvested for timber and other purposes in the 19th and early 20th century, so much so that in the 1940's less than 4% of the trees in PR were of primary origin. Finding a 100 year-old tree in PR is extremely difficult. Yet, in the middle of the Guánica Forest, about a couple of hundred meters off the beaten track, you can find a Guayacán tree that was already quite big when Christopher Columbus was still looking westward and imagining riches of all kinds.

(Katie McKenna 2011)

The Guayacán Centenario tree survived the axe probably because of a combination of its inaccessibility and its gnarly appearance. Either way it reminded us a lot of the Tree of Life from the movie Avatar.

Closer to the main trail Skip introduced us to the Century plant (Agave sp.). While this plant does not live as long as it's name suggests, it does manage to survive for about 20-30 years. At the end of its lifetime, the plant produces a flowering spike that can grow as tall as 25-30 feet in height. Once it flowers, the plant having completed it's lifecycle, then dies.

(C.S. Manish 2011)

We were lucky enough to see a few of these spikes.

(C.S. Manish 2011)

In a dry forest, leaf litter is harder to break down because of the lack of moisture. One of the most important agents that breaks down leaf litter in the Guánica Forest are termites. It is not uncommon to see termite nests up in the trees, where they are protected from predators.

(Sami Wysocki 2011)

Termites make protective channels of mud, tunnels if you will, along the tree trunk that serve as service roads to the forest floor.

(Sami Wysocki 2011)

From the Guánica Dry Forest, we then went to Tamarind Beach to observe a forest of a different kind.

(Miranda Beran 2011)

High-velocity winds come rushing in off the Caribbean Sea onto the shore near Tamarind Beach. Consequently, plants cannot afford to grow too tall. Instead they grow sideways or slant away from the ground, a property known as thigmomorphogenesis.

(Andrew Jacobsen 2011)

Since the vegetation here is closer to the ground, trees can live for hundreds of years and yet not be taller than a foot or two. Instead they creep sideways, growing in very small increments each year. The Dwarf forest at Tamarind Bay has to be seen to be believed.

(Katie McKenna 2011)

The most surprising sight for us was to see that cacti can be found right next to the ocean.

(Lorissa Panowicz 2011)

There are many kinds of cacti that dot the landscape and coexist happily with the shrubs and trees.

(Sami Wysocki 2011)

After the hikes to the two different forests, the students had some fun cooling off in the waters off Tamarind Beach.

(C.S. Manish 2011)

The waters were quite rough and choppy. "I know how a coconut feels," said SW. Considering how this coconut was being tossed around, I agreed with her.

(C.S. Manish 2011)

Since it was KM's and MB's combined birthday, we had the obligatory cake-cutting moment when we got back to Alegre.

(Andrew Jacobsen 2011)

I had previously decided to treat the party to a Puerto Rican dinner at a local restaurant, so we got ready for that. Everybody dressed up and we had an (extended) photo session before we left for Pimiento's Cafe.

(C.S. Manish 2011)

Naturally, we had to take a photo outside the house we stayed at.

(Andrew Jacobsen 2011)

The food was excellent and everyone tried a different dish, enabling us to taste a wide variety of dishes.

(C.S. Manish 2011)

We came back from the restaurant well-fed and content and ready for the next day when we would visit the exotically named Laguna Cartagena, among other places.