After two weeks in the heat of Las Cruces, I could not wait to go to the cool of the mountains, and experience an elevation and temperature much closer to what I would experience at my school in Vermont. My very first class in college was Mountains of the Northeast, so I was excited to see how the mountains I am familiar with from home compared to those of the tropics at a lower latitude. We spent a few days at Cuericí Biological Station learning about the wet montane forest, which is higher in elevation and is often submerged in the mist of clouds. One day we went to the Páramo, or the subalpine zone, of the Talamanca mountains.
The weather of the Páramo is highly variable and changes very quickly. The day of our hike up the mountains it was rainy and cool due to a storm from the Pacific. With no view of the surrounding area, all of our attention was on the plants and learning about their abilities to survive in such harsh conditions. Our guide through the Páramo had grown up here exploring the mountains so she could share not only facts about the plants but also her own stories from when she was a kid of testing to see which fruits on the plants were edible. Thanks to her we were able to eat some berries from the plants we were simultaneously learning about.
The plants that grow in this area need to adapt to the cold, wind, and high UV exposure that their environment entails. The first noticeable characteristic of these high altitude plants is that they are low growing. After looking from the understory all the way up to the canopy of Las Cruces, my eyes now only needed to scan up to a meter above the ground to see the tops of the plants. By growing low to the ground, plants are able to avoid the worst of the winds. Often forming mats along the ground, they also share warmth and protection with one another. So while it is not dense vertically, the Páramo can have dense patches of vegetation along the ground. And where there are not plants growing, there are dark rocks, on one of which we found a Sceloporus sp. lizard. Animals also need to adapt to the conditions of the Páramo, to avoid both the cold and extreme sunlight. Few animals are able to survive in the harsh and variable conditions of that elevation, because of the challenge of maintaining body heat, so we were lucky to see the lizard.
Another common adaptation for these plants is to have smaller leaves to prevent too much UV radiation. Many leaves in the lower elevations are bigger than me, whereas on the Páramo, smaller leaves are favored. The leaves of these plants are also often pubescent in order to increase their boundary layer. The boundary layer is the space surrounding the leaf, so a larger boundary layer keeps plants warm by directing the flow of air away from the leaves. I was glad to have a rain jacket as my own boundary layer on our hike to help protect me from the cold rain.
By the end of the hike I realized that the high elevation plants of the tropics have adapted many of the same characteristics of those in northern high elevations. In both instances the high elevation plants are related to the ones below, just modified for the different conditions. So while the species of the north and south mountains are different, they have similar appearances with short, small leafed, often hairy plants.
A couple of days later we were fortunate enough to get to go back to the Páramo on a clear day so we had a view all the way out to the Pacific. I could then see beyond the rocks and high elevation plants to observe the transition to the denser, taller forests below. I hope that I will one day be able to do research on the differences between these southern high elevation plants and those in northern high elevations, as this would allow me to work both in my old home and my new home here in Costa Rica.