10 January 2017 Manipulating the Dry Valley Soil

Getting to F6 Camp

Today four of the team members were at F6 Camp on the south side of Lake Fryxell in Taylor Valley. Travelling to F6 Camp meant another stunning helicopter ride. This time we flew over a large iceberg that had previously broken off of the ice shelf and subsequently froze into the sea ice which is still intact all around McMurdo.

This iceberg is trapped in the sea ice between Ross Island and the Dry Valleys of Antarctica.

Stoichiometry

Our main objective in visiting the F6 Camp was to apply treatments to an experiment referred to as the Stoichiometry Experiment. Stoichiometry is a term that describes the relative amounts of chemicals in a reaction. In this case the term is used to describe the relative amounts of nutrients available in the soil and how those nutrients affect or limit the productivity of the soil.

F6 Camp in Taylor Valley with a view of the Canada Glacier in the background.

Limiting Nutrients

Most gardeners are familiar with signs of missing nutrients in garden soil and the need to add occasional fertilizer to keep plants healthy. I know in my garden at home if I don't have enough nitrogen in the soil my corn doesn't grow very well. Fertilizers often contain Nitrogen, Phosphorus and Potassium; these nutrients are often limiting the productivity of the soil because they are in short supply. One nutrient that is not considered in fertilizers is Carbon. Plants use photosynthesis to take carbon from the air and turn it into sugars and other organic molecules. In the Dry Valleys there aren't many plants so Carbon becomes a limiting nutrient in the soil. Soils at F6 Camp are also low in Nitrogen. The Stoichiometry Experiment is set up to figure out what impact adding nutrients one at a time or in combinations has on the soil community.

Looking towards the Commonwealth Glacier and Lake Fryxell from the F6 stoichiometry plots.

Experimental Design

The experiment is set up in two separate locations in Taylor Valley and F6 Camp is one of those locations. Each treatment plot is 1 square meter and the plots are laid out in 8 rows of 13 plots. The plots are designated in one of seven ways: Carbon (C), Nitrogen (N), Phosphorous (P), Carbon & Nitrogen (CN), Carbon & Phosphorous (CP), Water (W), Un-amended (U), and Buffer (b). The buffer plots provide a buffer zone between adjacent treatments to help account for any transfer of nutrients between plots and they are not treated. The water treatment and the un-amended treatment are controls for the experiment.

Schematic illustrating the setup of the F6 Stoichiometry Experiment.

The W, C, N, P, CN and CP plots all receive 5.6 Liters of solution containing the appropriate nutrient. The solutions are poured from a jug into a circular area defined by an ITEX chamber (a plastic conical structure). The ITEX chamber is a convenient way to define the area of soil that needs to be treated and it also blocks the wind from blowing the solution around as you pour.

Josh Heward adds nitrogen to an experimental plot near F6 Camp in Taylor Valley, Antarctica.

Long-term Research

This experiment was started in 2008. The relatively low productivity of the Dry Valley soil ecosystem and the short amount of time each year when there is water available in the Dry Valleys means that it can take many years before you see the effects of an experiment. Long-term research is critical in situations like this.