You are currently browsing the monthly archive for December 2011.
Byron, Jeb, Eric and Martijn went out into the field recently to sample and treat the Stoichiometry Experiment. This experiment is replicated at two different sites within Taylor Valley; one near Lake Fryxell and one near Lake Bonney, at the Bonney Riegel. The purpose of the field experiment is to investigate which nutrients are most limiting to Antarctic Dry Valley soil communities and the ability of soil communities to respond to nutrient additions. You can read more about the sampling of this long-term experiment during the 2010-2011 season on Dr. Becky Ball’s blog http://polarsoils.blogspot.com/2010/12/fertilizing-polar-desert.html.
Because Dry Valley soils are generally carbon limited, we wanted to test if i) carbon additions will increase soil respiration (a measure of the level of activity of organisms) and biomass of soil communities, ii) the nutrients nitrogen and phosphorus alone will not increase the activity of organisms and iii) elevated levels of nitrogen will increase nematode mortality. In addition, the soils of the Bonney Riegel have high nitrogen and ow carbon and phosphorus content and are expected to respond to the addition of carbon, or carbon and phosphorus, but not to nitrogen additions. Fryxell soils on the other hand have a high phosphorus content, and nematode communities are expected to respond most to carbon and possibly carbon and nitrogen additions, but not to carbon and phosphorus additions.
The experimental design consists of different plots that are organized into replicate blocks within each site. Each plot is treated in one of the following ways:
1. An unamended control
2. Addition of water only as a control for the water that is required to add the nutrient elements
3. Addition of carbon in the form of mannitol, a compound found in algae
4. Addition of nitrogen
5. Addition of phosphorus
6. Addition of both carbon and nitrogen
7. Addition of both carbon and phosphorus
The team went to the Fryxell site on Wednesday, December 21 and then to the Bonney site on Friday, December 23. They first sampled all of the plots. The topmost layer of the soil was first collected for measurement of the chlorophyll a concentration, which helps provide an estimate of the photosynthetic productivity of the soils. Soil samples from each plot were then collected to a depth of 10 cm, to be used in measuring soil chemistry, soil moisture and extractions of the soil animals present. The samples were brought back to the Crary Lab at McMurdo station where the soil invertebrates were extracted and counted. After sampling the soils, the nutrient treatments mentioned above were applied to the plots.
The weather on both days was very nice, and the landscapes were stunning as always. On Friday at Lake Bonney, the helicopter was a little late to pick the team up at Lake Bonney, so there was some time to explore the area. Martijn walked up to the edge of the Taylor Glacier, named after Griffith Taylor, geologist and leader of Scott’s Western Journey Party of the British Antarctic Expedition (1910-14). The glacier had been discovered by Scott during the British National Antarctic expedition (1901-1904) but Scott thought it was a part of the Ferrar Glacier at the time. Taylor, however, discovered that these were not parts of the same glacier, but two glaciers side-by-side.
While the rest of the LTER Soils team was busy setting up the new experiment near Many Glaciers Pond, Zach, Jeremy, and Martijn went to sample soil and apply scheduled treatments at the Biotic Effects Experiment (BEE) plot near Lake Fryxell at F6 in Taylor Valley, one of three locations where BEE plots have been established in the Taylor Valley. All of the BEE plots were established during the 1999-2000 season.
F6 is the name for a U.S. field camp situated near where Van Guerard Stream empties into Lake Fryxell. Field camps have been established at strategic locations throughout the Dry Valleys to support ongoing scientific work in the area. They serve as camping, staging, and emergency survival locations for scientists.
There are four different treatments at the BEE plots:
- Control (no treatment)
- Soil warming with ITEX chamber
- Water added
- Soil warming and water added
The purpose of the experiment is to see how the soil ecosystem throughout Taylor Valley will respond to environmental change. As predicted by climate change models, it is expected that the soil temperature will increase and that more water will be present in the soil.
The first step was to sample soil from the 24 plots. A few of the plots still had ice right underneath the surface from adding water last year! We had to get creative to chisel out enough soil to sample. Next, we needed to add 5.6 liters of water to the “water added” plots. Our final task was to perform maintenance on the ITEX chambers by making sure that they were all strapped down securely. Strong katabatic winds in the Dry Valleys can destroy experiments if they are not securely anchored.
We were able to finish up our work quickly so the helicopter picked us up a little bit early.
The Wormherders are back on the Ice!
The crew this season consists of Dr. Martijn Vandegehuchte and Zach Sylvain, both from Colorado State, joined by Dr. Byron Adams, one of the LTER co-PI’s from BYU, and his student Jeremy Whiting. We’ll also be working with other members of the McMurdo LTER Soils Team throughout the season.
Since this is their first season on the Ice, Martijn and Jeremy had to do snow school, perhaps more famously known as “Happy Camper” school. The basic premise is that snow school prepares you to survive in Antarctica for a few days in case you are in a survival situation. You also learn how to set up a proper field camp. The class lasts a full day and half, including an overnight stay on the McMurdo Ice Shelf.
Martijn built a snow trench, which really ended up being more like a cave. He crafted stairs, built a cold sink (a dip in the cave for the cold air to settle), and had a heavily fortified roof. Despite the snowfall during the night, he was nice and warm inside his trench.
Jeremy reported that he had a great night of sleep. Everyone was disappointed that he slept in a tent rather than in a snow trench. He said that snow school was a lot of work but contained valuable training for camping in general, especially snow camping.
We have already returned from our first sampling trip in the field. We went to the south side of Lake Hoare in Taylor Valley to sample the soil of two experiments– the Long Term Monitoring (LTM) plots and the algae addition plots. The LTM plots are a collection of 64 1-meter square plots with a variety of treatments applied to them. The treatments include increasing temperature, adding water, adding simple table sugar (sucrose) mixed with water, adding natural sugar (mannitol, a sugar found in algae) mixed with water, and different combinations of each of those. Additionally, there are plots established as controls. The experiment was set up during the 1993-1994 season and the treatments discontinued during the 2004-2005 season. Since then, Wormherders have continued monitoring the recovery of the soil ecosystem to document the changes. Later, actual dried algae (without water) was added to a separate set of plots and another series of controls were established as well. These 16 plots became known as the algae addition experiment, or just the algae plots. The experiment was established in the 1994-1995 season and was decommissioned at the same time as the LTM experiment, so our current sampling is to document the recovery of the soil ecosystem just like with the LTM plots.
After the sampling was complete, we dropped off Byron at a new experiment being established near Lake Fryxell while the rest of the Wormherders returned to McMurdo for sample processing. We’ll talk more about the new experiment in a later post.