Las Cruces, pt. 7: Forest fragment fun

Thursday morning (2/2) we started the day early and drove out as a group to a pasture about 20 minutes from Las Cruces. As in many parts of Costa Rica, the land here had been cleared of trees to graze cattle; however, areas with steep slopes or otherwise difficult features were left untouched because they're more trouble than they're worth to clear. This leaves a bunch of forest fragments behind, which we went to see. 

Susan, our professor (center, back row), teaching us about fragmentation.

 While it's good that some areas of forest are left behind when land is being clear-cut, fragmentation still has lots of negative effects on forest ecosystems. By creating lots of extensive edges that would not exist otherwise, fragmentation alters microclimate, species composition, and species interactions in forests. For example, an "island" of fragmented forest can become sunnier, warmer, drier, and breezier up to 10 m in from the edge on all sides. As a result, animals and plants that rely on shade or canopy cover for food or to avoid predation have even more of a reduced habitat than they already did due to the initial fragmentation. Furthermore, the altered microclimate can be favorable for species of plants and animals (as well as diseases) that normally wouldn't be a part of the forest ecosystem. These invasives can outcompete the existing flora and fauna and exacerbate their local decline. Fragmentation also tends to decrease gene flow between previously contiguous forest patches, generally decreasing the fitness of isolated populations. Basically, fragmentation is not good!

Classmates walking through the pasture after visiting a fragment of secondary forest.

The site of our field trip. You can see how the clear-cut land borders up against a fragment of primary forest (left).

After getting to explore the pasture and remaining forest patches and experience the effects of fragmentation firsthand, we sat down and did another field writing exercise, this time about how fragmentation would effect a species of our choice throughout its life cycle, including growth, food acquisition, predation risks, and reproduction. When we finished our writing, we got ready to head back to Las Cruces.

By the end of the exercise, the fog had begun to creep in! It looked pretty cool blowing around in the valleys.

While we'd taken two OTS trucks out to the pasture, one had just dropped us off and returned to the station. This meant we only had one car on the way back, which was definitely not big enough to fit all 28 students, plus our two professors, TA, and driver. We planned to do shifts, driving some people back each time, dropping them off at Las Cruces, and then returning to pick up more. Because it was a beautiful day, I decided to walk most of the way, and was rewarded with amazing views.

Enjoying the scenery while headed back towards Las Cruces.

After lunch, we had a lecture on forest classification, and learned to identify different forest ecosystems using the Haldridge Life Zone system, which based mainly on latitude, altitude, and precipitation. It finally made sense why our professors kept referring to the forest as a "Tropical Premontane Wet Forest" instead of just a rainforest! Haha.

A chart of the Haldridge life zones. (Click to enlarge.)

Friday was a relatively average day, with a review of statistics in the morning, a tutorial on how to use JMP in the afternoon, and a lecture about beetles and flies in the evening. Since I took statistics at Reed already, am totally comfortable using JMP, and am not particularly into studying insects, I was a bit nonplussed with the combination of three uninteresting things into one day. Plus, we had essentially no physical activity, either, so after our statistics workshop Tessa and I decided to be motivated and go for a run, which turned out to be fun and also (unsurprisingly) very beautiful. So far I've been hard pressed to find a place in Costa Rica that I don't think is beautiful. Haha. Friday may not have been the best day, but we ended it by packing for an overnight trip to a new field station!