The final gira to western Santa Elena Peninsula went quietly and smoothly. By this trip I’ve nailed down the major logistics including knowing when the tide is low enough so we don’t have to swim to shore. For this final trip we also had the company of my postdoc advisor Prof. Susan Harrison from University of California at Davis who shed light on the process of serpentine formation. According to Susan the serpentine here in Santa Elena Peninsula is partially serpentinized. In a nutshell, during the transformation of ultramafic rock to serpentine, excess iron remains which subsequently becomes oxidized (reacts with oxygen) to form iron oxides (rust is a type of iron oxide, for example). Translation: red soils. She also suspects that the Islas Murcielago complex , including Isla San Jose, were formed from underwater eruptions that came into contact with sea water forming pillow like structures (also known as pillow basalts which are fairly common around serpentine formations like Santa Elena). I’ve read about this theory before from works by Prof. Percy Denyer of Universidad de Costa Rica here, here, and here.
One of the main goals for this trip was to collect soil samples from the 15 vegetation transects along the elevational gradient from sea level to 720 meters. Some theories suggest that serpentine soils are highly homogenous, or similar, regardless of where the soils are measured. But this seems difficult to reconcile after seeing how variable soil depth can be in these mountains. Once I export the soils and send them to an analytical lab for nutrient analyses, I’ll begin to understand how plant diversity and function change with elevation and soil nutrient content.
Another goal of this trip was to finish collecting and processing plant traits. A back of the envelope calculation puts the number of species at 140 and 3000 individual leaves measured for leaf thickness, leaf toughness, and specific leaf area. These measurements form part of a growing database that I will use to link plant traits to caterpillar diversity.
The final goal was to find a helicopter landing pad in the middle of Cerro Santa Elena. This was no easy task as most of the topography is too steep or too rocky or too densely vegetated for a helicopter to land safely. Many of us are wildly interested in black-lighting for moths in these mountains but bajando del bote nadando y subiendo la montaña with several car batteries, enough water and food, and then bajando with bags of mariposas is likely not the mango bajo. Not even close. We found several places where a helicopter might be able to lower down equipment and maybe people but I remain skeptical, secretly hopeful.
Al final, these three giras have been surprisingly successful. There’s no telling what remains undiscovered in this vast, unexplored corner of Costa Rica. Give me a few more years. A lifetime.