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 helicopter leaves after dropping off the wormherders at F6 Camp near Lake Fryxell

Jeb carries a jug with nutrient solution from the landing pad next to F6 Camp to the experimental site.

The Von Guerard stream drains into Lake Fryxell with the Commonwealth Glacier in the background.

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.

Jeb and Martijn are using jugs with a pour cap and open top chambers to apply nutrient solutions to the soil plots.

The edge of Taylor Glacier.

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