Antarctic Experiments Include the
LI-COR Photosynthesis System

The middle of austral summer, when high temperatures are around 33°F, is a perfect time to explore the biology of Antarctica's McMurdo Dry Valleys, according to Dartmouth College post doc Becky Ball. For the last several years Dr. Ball has spent the months of December through February at the McMurdo Dry Valleys Long Term Ecological Research site, where the landscape looms large, but a 1mm nematode sits at the top of the food chain.

What is so interesting about the biology of this extreme environment, which is among the coldest and driest on Earth? "The Dry Valleys represent a region where life approaches its environmental limits," Ball says. "Dry Valley soil communities are subject to low temperatures, limited precipitation, and salt accumulation." The soils also exhibit highly heterogeneous properties, hydrologic regimes, and biological composition, both spatially and temporally. Ball and other scientists are working to relate this variability to "geological legacies and to the resulting complex distributions of invertebrate communities" as part of the NSF-funded McMurdo Long-Term Ecological Research (LTER) project under co-Principal Investigators Dr. Ross Virginia and Dr. Diana Wall.

Her Antarctic research focuses on three hypotheses: to examine the how soil nutrients and components influence biotic abundance and activity; to understand how soil CO₂ flux is related to soil moisture, texture, temperature, and biota; and to better understand how this ecosystem will respond to a changing global climate. To explore these hypotheses, Dr. Ball and her colleagues use both an LI-6400 Portable Photosynthesis System, and more recently, the LI-8100 Automated Soil CO₂ Flux system.

There are no vascular plants in the Dry Valleys, but there is plenty of biology to study - when summer comes around and the ephemeral streams start flowing, mosses emerge as the primary producers of the ecosystem. In fact, moss and algae are among the most prominent above ground organisms in the Dry Valleys! Becky and her team use the LI-6400 to investigate how much carbon and nutrients are taken up by the mosses, and how these precious resources are released when the mosses die. They also are trying to determine how the mosses respond to an increase in the availability of nutrients in their surroundings.

Becky says that the measurements of CO₂ flux in the Dry Valleys provide insight into the physical controls of the carbon cycle, which tend to dominate biotic components in extreme environments. With a custom-built transparent cuvette affixed to an LI-6400, Becky and her team are able to measure photosynthesis and respiration from algal and moss communities growing in the rocky soils. They also use an LI-8100 to measure soil CO₂ flux. "We use both the survey chamber for spot-measurements for treatment effects at our experimental plots, as well as the long-term chamber to measure diel patterns of CO₂ flux from soils."

Becky describes the Dry Valley soils as a relatively simple ecosystem, in which the mechanisms that control basic soil functions can be more easily identified than in more complex systems. By studying the Dry Valleys, she hopes to learn more about the basics of how soil ecosystems function. In addition, the extreme conditions experienced in the Dry Valleys are the closest Earthly analog to soils of Mars, and Dry Valley soils are often used as a correlate for Martian soils.

While the Dry Valleys are a tough place to work, and there is not much free time in the short field season, there is something in Antarctica to suit almost anyone's personal preferences. For the history buff, relics of Antarctic explorers, including a shack built by the Englishman Robert F. Scott, provide a glimpse into the hardships endured by those early visitors. One shack, built in 1902, stands almost perfectly preserved in the cold and dry climate, complete with artifacts from early expeditions. For the athletically inclined, the Scott's Hut Race, which is a 5.2 mile run around McMurdo Station provides some friendly competition. The very ambitious can run the annual McMurdo Marathon - a full marathon on ice and snow! Musicians and music lovers can enjoy McMurdo's music festival and New-Years celebration - IceStock, which features the local talent. McMurdo Station also boasts a 9-hole disc golf course, a bowling alley, and the continent's only ATM machine.

On chilly evenings, in this cold environment - where water is so scarce that even showers are placed on hold - scientists find ways to turn the every-day into amusement. Without showers, the biologists' hair seems to take on a life of its own, and it is affectionately referred to as "camp hair." This year, visitors to Becky's blog judged the 2nd Annual Camp Hair Contest. Visit her blog to see who won the "camp hair" contest and to read the latest on her research at http://polarsoils.blogspot.com/.

For more information...
• LI-6400XT Portable Photosynthesis System
• LI-8100 Automated Soil CO₂ Flux System
• Polar Soils Blog
• McMurdo Dry Valleys Long Term Ecological Research (LTER)

Thanks to Becky Ball, Postdoctoral Research Associate, Dartmouth College, Environmental Studies Program, for contributions to this article, and to Elizabeth Traver for the photographs.