DBH to Height

I’ve spent the last week making regressions for different data in R. Actually using R and manipulating data is quite easy. The hard part is trying to get good data. There are multiple years of data entered by multiple people at different times and in different ways. The result is a bit of a nightmare when it comes to using the data (and I have, in fact, had nightmares about it). There are some trees that have a diameter at breast height( DBH) but are only a foot high, there are some trees that have the same ID number as a different tree, and there are some trees that have simply gone missing. A big part of this summer will be finding if the funky data are from something being lost in conversion from PDF to Excel, or if there were errors recording data in the field.

[Read more…]

Some Direction

I was a little hazy on what I’d actually be doing this summer. Would I be helping someone else with her research? Would I be using data that was already collected? Or would I be messing around until I had the opportunity to head to Maine and Vermont to collect new data? It turns out I’m doing a little bit of each. There is an incredible amount of data being used for a matrix model that has been in the works longer than I’ve been at W&M, and I am helping sort through it, picking out funky pieces of data and marking them so they can be checked with the real trees when we take the trip to Maine. I am also using the current data to practice my modeling skills. One goal for the summer is having a functional model for the Maine data. I am using a statistical program, R, that is very different than Python ( the language I’ve used so far in my CS classes), and I spend a significant amount of time just trying to find proper syntax and functions for the things I want to do. Once more data is collected, there will be two years of data collected from the Vermont site, and I spend time this fall building a new model for a new set of data.

[Read more…]

Introduction

Hi, I’m David McPherson and I’m doing research this summer with Charles Center funding.

The American chestnut used to be a dominant species of eastern forests in the US. It composed a significant portion of the canopy, and its nuts provided food for a variety of creatures, from rodents to humans. The introduction of the chestnut blight, which eliminated the nearly all canopy American chestnut trees, pre-dates modern forest ecology, and consequentially the significant impact the species had on the forest is not known. The chestnut is a flagship tree species, and for decades numerous groups have been trying to find ways to develop blight-resistant trees to reintroduce to the wild. For the reintroduction of blight-resistant trees to succeed, it is necessary to understand the ecology behind the chestnut. Some populations in New England have, so far, been spared the blight due to both isolation and the cold winter temperatures. While the blight has a presence in some populations, it has not yet been able to completely upset the ecology of these forests as it has done in warmer climates. This unique situation enables the modern study of forests containing chestnut trees.

[Read more…]

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.

[Read more…]

Chestnuts #2–Midseason

After two days of measuring seedlings, two major trends in survival became apparent. First, almost all of the seedlings planted in the forested plots were dead. I also noticed that they tended to die from the top down, with new stems regenerating from near the base of the original stem. Second, and much to my surprise, the fenced-in plots (protected from deer browsing) had actually suffered far higher rates of mortality than the unprotected plots.

[Read more…]