How Many IGERTeers Does It Take To Haul 1,000 Pounds of Water?
When I applied to graduate school, I had my heart set on studying how pesticides bio-accumulate in squid after being carried from one side of Costa Rica to the other via the seasonal trade winds. After many false starts and dead-ends (and almost five years later) the focus of my dissertation is on the effects of altered flowering phenology on plant-pollinator interactions and plant reproduction. To say I changed course would be a major understatement. Would my squid idea have worked out? Probably not. Had I done any research into the topic? Pfft, of course not! It just sounded like a fun idea. So how did I go from a crazy, squid-based research idea to a more interesting, practical, and basic-science oriented question? Through a lot of trial-and-error and helpful advice from my committee and advisor. Thanks, guys! But chasing kooky, quixotic ideas and getting pulled back to earth is all part of the graduate school experience. And it’s a healthy experience, I think. I have to admit it is satisfying to look back and see the progress that I have made, and it is equally satisfying to see the progress that the other members of my cohort have made.
Julia Bradley-Cook, a friend and fellow IGERTeer, has just wrapped up a field season here in Greenland. We were lucky enough to spend some time with her in the field before she finished what will likely be the last field season of her dissertation. It was an amazing experience for me because Julia and I are in the same cohort in the Ecology and Evolutionary Biology (EEB) program at Dartmouth, and I have seen her research develop over the past four years through her talks and presentations at Dartmouth. But this was my first time seeing Julia’s science first hand, in the field. And while my research dramatically changed directions (several times) during my first couple years as a graduate student, Julia is literally doing the polar opposite of what she had initially set out to study.
I clearly remember Julia’s first talk at Dartmouth, in which she proposed studying soil carbon flux in the dry valleys of Antarctica. She went to Antarctica, tried out her ideas, and like most graduate students failed to generate data that would turn into a dissertation. Sad, but true. Then she decided to follow a similar line of research in an environment that was better matched to her research question: in the arctic rather than the Antarctic. Julia’s current work focuses on how arctic soil respiration will respond to an increase in precipitation. She explained to us that the atmosphere contains about 750 gigatons carbon. Soils, on the other hand, have about 3,200 gigatons globally. That means that soils hold over four times as much carbon as the atmosphere! Mind blowing. What’s more, about half of all that carbon is in arctic soils, if you include boreal forests. Climate change models predict that precipitation in Greenland will increase by 15% by 2050 and by 50% by 2100. How are the arctic soils going to respond to this increase in precipitation? That is one of the main focuses of Julia’s dissertation, and to investigate the question she is adding water to 18 plots, each paired with a control plot, and then measuring soil respiration using an infrared gas analyzer.
So far she has been adding 6 liters of water to each plot, which reflects a realistic increase in precipitation over the next 90(ish) years. Her results have been quite interesting thus far, although some could argue that the results are a bit ambiguous. So she decided that she needed to take a sledgehammer approach: add an enormous amount of water, and see how soil respiration is affected. That way there would be no ambiguity as to the response to water itself, and then she could use those data to help interpret her more realistic water additions. For the sledgehammer approach, she decided to add 24 liters of water to each plot over the course of a very short period of time and then take soil respiration measurements every ~12 hours over the following few days. 24 liters of water * 18 plots = 432 liters of water total. Remember that 1 ml of water has a mass of 1 gram, so 432 liters of water has a mass of 432 kilograms. What’s more, the water needed to be hiked up to her sites from a lake. Woof. That’s a lot of work. And it would have been nearly impossible for Julia and her hard working assistant Leehi to have done it by themselves. Luckily, IGERT cohort 4 (later named “Totally Awesome Cohort” by Ross) was there to help!
Once we hiked up to the sites carrying a backpack filled with five gallons of water, we needed to get the water onto the plots. We used two techniques for this, one slightly higher tech than the other. The first was to dump the water, one liter at a time, through a colander. The colander helped to spread the water out as it fell, much like a sprinkler. The second approach was to use a backpack with a pump-sprayer attached. I have used similar backpacks before, but this was a new design for me. Apparently the one we were using is made for firefighters. I have to say, I feel bad for those firefighters. The backpack would leak about a third of its water down the back of the wearer, and using the pump spraying was surprisingly draining! But technical difficulties aside, we managed to haul all the water up and apply the treatments to her plots. The next few days were an insane push for Julia to take all of the necessary measurements and prepare for her departure, but she managed to pull it off. Congratulations, Julia, on wrapping up another field season, we can’t wait to see how the data turn out!