Chestuts #3–Late season and current thoughts

Long days of solitary work tend to encourage wandering thoughts. Plenty of them are ridiculous—“hey, maybe if I manage to selectively kill only the mosquitoes that land on me, I’ll be able to select for a new strain that won’t feed on people!”—but some are more serious. One of these more serious thoughts came to me on a particularly hot day when I was feeling drained and unguarded. I knew that the goal of the chestnut reintroduction program is to create a hybrid blight-resistant tree that will be capable of establishing itself and spreading in the environment with a minimum of human assistance. When you stop to think about it, as I did then, this is very close to the definition of an invasive species. If the reintroduction effort were to succeed, the shock to the ecosystem from the return of the species could potentially have cascading effects, as is so often the case with any change in an environment. And even if the new chestnut is able to readjust to its former niche without incident, that 6% foreign DNA in the average individual produced by the Foundation might be just enough to significantly alter the species’ ecological behavior and cause unpredictable disruptions to the habitat. These are just conjectures, of course. They have not been tested and cannot yet be tested. But they are necessary cautions to bear in mind as work proceeds.

In the later days of my project, I turned my attention to a few new tasks. First, there were the soil moisture measurements: for the first four days after a rain event, I would visit the plots each day with a thermohygrometer (a device which uses electrical conductivity readings to gauge the percent water saturation of a soil sample) and sample one randomly selected square of soil from each. I was curious to see whether there was a significant difference in water retention between the cleared and forested plots, and to see if any trends could be correlated with seedling growth rates. I also began the large task of soil analysis. This was really two tasks: I would collect the samples and separate out the roots, and then send the remaining dirt to A&L Great Lakes labs for a basic round of nutrient availability tests. I intended to use belowground root mass as an indicator of belowground competition-the amount of strain placed on the chestnuts by the presence of other species’ roots. Together with my studies of aboveground competition (discussed in my last post), these results would form a reasonably complete profile of the seedlings’ botanical environment.

Collecting soil for this process proved to be a tricky business. I used a device called a soil corer—which is basically an open cylinder with teeth on the bottom and a handle on top for driving it into the ground. It was physically difficult but I managed to finish the job after two long days in the field. I used heated ovens to dry the dirt I collected (and even after this process, all the samples together still weighed more than 60 pounds) and then sifted the samples to remove the roots, which I weighed. In the process, I noticed that the samples from the cleared plots tended to contain large masses of fine roots, while the soil from the forested plots seemed to have fewer but thicker roots. On my very last day at Purdue four weeks ago, I gathered the samples for shipment to the lab, and covered in dust from head to foot, walked back to my dorm room for the last time.

Right now I am mired in the swamp of data analysis. Actually, the data from the seedlings is not yet complete: Harmony and the lab will make one final measurement in October which will provide us with a complete picture of the growing season. For this reason I am going to delay the posting of my final results. My intuitions about what they may be and why are scattered throughout these posts,  but my results will require a great deal more work before they can be wrought into scientifically sound conclusions. That being said, there are still a few conclusions I can make about the nature of my project. First, it was a good deal harder than I had anticipated. In previous summers I had done fieldwork and was well acquainted with the particular stresses–early mornings, biting insects, etc.–that accompany outdoor work. But this project was my first foray into self-guided work: I set my own schedule and priorities, and worked mostly alone in the field. This made for a newfound sense of self-ownership that I have never experienced before in my research endeavors, but it did come at the price of loneliness on some of the longer days. This summer was not always much like what I had expected it to be, but perhaps it would not have been nearly as valuable if it had been. And again, I must express my gratitude to Harmony Dalgleish and my other colleagues at Purdue, as well as to my advisors here at William and Mary, for helping make this possible.

Comments

  1. Morrison Mast says:

    Reading about your work reminds me how painstaking and even disheartening it can be to work on a reforestation project. During my research this summer I worked with an organization that was reforesting rural areas in Madagascar with native species, which is hard enough; but they were seriously lacking people with formal experience in raising and transplanting saplings. If you’re interested in volunteering on such a project, I’d be more than grateful to try and connect you with some people down there. It’s a good cause but hard work: these guys are protecting the little forests that Madagascar has left, and the human pressures are quite a challenge to deal with.

  2. Nick Schmedding says:

    Thanks for you offer! At the moment, though, I’m pretty tied up with other things and don’t think I’ll have time to travel to the other side of the world. But I can definitely empathize with their difficulties.