August 3rd: Field Day #1

Paul Stoudt

After a well needed rest following the Mendenhall Glacier hike day, we set off to meet up with Dave D’Amore, one of the leading soil scientists on the Western Hemisphere. We braved another quick hike through soft mosses and peat, and arrived at a lush open area which would be the location of one of our soil pits for the day. We then embarked uphill and the scenery and vegetation flipped from mosses and peat to thick vegetation and trees in a matter of meters. As we neared the second site, we found out why. With the increase in elevation, there’s a decrease in free standing water, which speeds up the process of decomposition. This process allows layers of soil to build up on top of a harder layer of gravel and silt often called the parent soil. Using a saw, we established a 1 meter perimeter and loosening the topsoil; the next phase was rolling the top layer back like a carpet, in order to access the rest of the pit.

Paul Stoudt and Kyle Sherbine roll back the top layer of vegetation while Ian Wolfe cuts any root systems that may be in the way, site labeled as SKI PEM in Juneau.

After the topsoil was rolled away, the pit was dug to about a depth of one meter, and then the analysis began. I had no idea prior to today that soil layers were called horizons, and that the number of horizons can be broken down even further by doing color analysis, testing for plasticity, looking at how the soil breaks apart and what shapes the clumps of sediment break into. This sort of process was done on both the uphill and downhill sites, and even though there was only about a 100 meter distance between them, the difference between the two sites was astonishing. This difference was due to the slope of the terrain, which I thought was fascinating. Even a few degrees difference can have drastic changes on the amount of vegetation and wildlife.

As any specialized field would, soil science has its own language. Depending on the number of horizons, soil consistency, slope of the area, and other varying factors, we can create specialized names for different sites. For example, one of our sites was called a PFO. For the majority of us that means nothing, but for a soil scientist, this gives you vital information about the area.

The uphill site at SKI PEM site. Just the slightest change in slope of terrain can drastically change the amount and type of vegetation growing there.

After taking a look and making descriptions on both soil pits, we split up and did methane and peat depth measurements. I think it finally hit me, why we’re doing these methane chambers. In Peru, I had no clue what I was doing, all I knew was that I had to stick this PVC pipe into the ground and take a measurement every six minutes. Now, I understand what we’re actually doing. We’re looking to see the fluctuations in the methane being released, and we can use those fluxes to calculate just how much methane is being released. We then compare that to the grounded carbon in the soil cores we took in both Peru and Alaska. I love that feeling you get when everything comes full circle and you actually learn something, and I had a lot of that happen during this trip.

Zachary Czuprynski and Colin Kelly take a methane sample in the downhill section of the SKI PEM site in Juneau, Alaska.

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