I’ve written all these posts about fun weekends and musings about Panama, but I haven’t actually written about the real reason I’m here this summer, my thesis project. This project has been brewing in my mind since November, when I first e-mailed my now advisor. I wrote two her with a couple of big ideas in my head. I was interested in studying how plants use water, and I wanted to look at that changes as a forest grows after it’s been cut down for a period of time, a process known as secondary succession. And I wanted to go to the tropics. That was the starting point, and after months of e-mails and reading and grant applications and frantic practice measurements, I had a project. I was going to work in the Agua Salud secondary succession chronosequence (basically, areas of forest at different ages, to study how processes change with age without having to wait for 30 years), and I was going to study a couple of simple physiological traits and collect leaves to study anatomy and chemical content … of palms. My professor likes palms (she did her Master’s thesis on them), a post-doc in our lab is going to be studying palms, palms are everywhere in the tropics!
Of course, I got to Panama and two different researchers on the project basically said that palms would be really difficult to study in their transects – it would be hard for me to learn how to identify them, hard for me to get to them, and be a lot of work for what would probably not yield very interesting results because I’d have suck low sample sizes. They suggested I consider something like melastomes instead – very common trees and shrubs with a really distinctive pattern of the veins in the leaves.(They’re also not monocots, which makes the title of this blog kind of silly now, but not much I can do about that!) It would be easy for me to learn to identify them and easy for me to get to transects (20 by 50 m rectangles of forest where all the trees are tagged and identified in a database) where I would find them, which would leave more time for actually taking measurements. I spent the first three weeks I was here learning how to identify my species, learning my way around the transects, and helping out on another project.
I finally felt confident enough (and time-crunched enough) to start my own collecting last Monday. I’m collecting in six transects, two each of three different age groupings. I spent my mornings last week and this Monday finding 5 samples of each of my species in the transects, cutting off the tips of branches to get enough leaves and putting them in ziploc bags so they wouldn’t lose too much water between cutting and getting back to the house.
The kinds of sites I'm working in this summer.
After lunch and a shower, I’d start working – cutting two leaves off of each sample in water, letting them sit in water for a minute and then quickly transferring them to plastic bags, where they’d sit, sealed, for about an hour to let the water equilibrate in the leaf. Then I’d start measuring how quickly water evaporates from the leaves, which sounds exciting but really meant I had to sit for four hours, weighing each of my 40 or so leaves once every 20 minutes. It gets kind of tedious, but a lot of it was spent, me, in the house alone, music blasting, and pending comments from my professor to the contrary, I’m done with that part of my project. Water loss rates show how the leaves would respond to drought conditions or low water conditions by measuring how quickly or slowly they dry out – leaves are constantly losing water in nature, and it’ll be interesting to see if the rate of this water loss changes depending on the age of the forest they were growing in.
After all those measurements, there was some data clean-up to do, then taking photographs of all my leaves with a scale bar included, to calculate size and area later, then putting them in envelopes to dry them later. I also took one leaf from each plant to put in alcohol, so that when I get back to Harvard I can look at them under the microscope to study their anatomy. Since I’ve covered all the sites I wanted to for this part of the experiment and I’m still waiting for a part to arrive to do the next part of the project, I’m working on organizing my hand-written notes from the field and catching up on things like writing this blog for the rest of the week. If the package doesn’t arrive by the end of the week, I’ll go the hardware store to buy a part myself, so experiment part 2 will start on Monday!
Some photos of my species!
Conostegia speciosa - fuzzy leaves and pink and purple flowers!
Conostegia xalapensis - small, dark leaves with brown ("chocolaty") undersides, and the berries are edible and yummy!
Miconia lacera - a small, shrubby pant with small fuzzy leaves (not as soft as C. speciosa) and cool looking pinkish flowers.
There are two more Miconia species, but they’re less photogenic – I’ll have to go through my pictures better to get images of them!
Jen Levye
