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Ecology

Uncharted Territory

Last October, a group of explorers crossed one of the last unknown expanses on Earth, the Cordillera Darwin in Tierra del Fuego, southern Patagonia. CNRS researchers took advantage of this unique expedition to collect samples that will help them understand how species adapt to the harshest climates.

There is little doubt the spirit of great explorers like Darwin, Humboldt, or Bougainville escorted the French expedition which left in late September to travel through one of the last unexplored regions on Earth, the Darwin Cordillera in the southernmost part of Patagonia.
The participants included mountaineers, researchers, photographers, as well as a filmmaker and a writer. As during the golden age of world exploration, all aspects of discovery were present on this six-week expedition, aptly called “A Darwin dream.”

uncharted territory

© Y. Estienne

In Patagonia, the team trekked a 100 km across passes, peaks, and unknown glaciers.



“The original idea came from a group of mountain guides who wanted to set up an expedition to an unexplored region of Earth. They settled on the Darwin Cordillera fairly quickly. Even though some of the coastal peaks of the range have been climbed, no one has ever attempted to cross the entire length of the range,” explains Sandra Lavorel, CNRS senior researcher at LECA1 in Grenoble. “Yvan Estienne, the expedition leader, wanted to add a scientific dimension to the project. That's how I got involved.” As an ecosystems specialist for regions with extreme climates, she planned the scientific project together with Sébastien Ibanez, also from LECA, who actually participated in the expedition and collected the samples. For once, it is the expedition itself that determined the direction of research and the experiments to be conducted. “The mountaineers wanted to leave at the beginning of spring for the Southern Hemisphere, when the snow bridges still fill crevasses. That's why we decided to base our research on trees, the only plant form that would emerge from the snow cover.”
More specifically, researchers decided to look at the subantarctic beech Nothofagus pumilio. Although this beech originated in the Southern Hemisphere and is well adapted to rigorous climatic conditions, it cannot grow above a certain altitude. “Research carried out in New Zealand on related beech species shows that the altitude limit is not only climatic—if the only issue were temperature, beech forests would be found at higher altitudes.” Previous observations in Chile and New Zealand point to an “invisible barrier” that beech trees cannot cross.
What is the true nature of this barrier? The scientists will attempt to test two hypotheses. The first one focuses on the availability of nutrients. If above a certain elevation trees cannot draw enough phosphorus and nitrogen from the soil, they are not able to grow. The other complementary hypothesis has to do with the microbial diversity of the soil. For nutrition and growth, trees rely on the activity of soil bacteria and fungi that recycle nutrients. The growth barrier for trees may result from differences in the abundance and species of microorganisms in forest soils.
During the one-month expedition, Ibanez, aboard the Nueva Galicia vessel which served as the expedition's logistical base, performed several excursions to take soil and leaf samples. He collected 120 samples, around 15 kg altogether, in the three plant communities that are distributed along an altitude gradient from sea level up to 650 meters. “This is the most difficult but also the most beautiful field work I've ever done,” he comments. “Sometimes, to reach the most interesting areas, it was necessary to cut a path through ice fallen from the glaciers, or to dig holes over a meter deep in the ice,” he adds.
The collected samples are now being analyzed at a Chilean laboratory2 which LECA has been cooperating with for several years. DNA samples will be brought back to LECA to be sequenced in order to characterize the local microbial biodiversity.
One of the key assets of this research is that it was carried out in virgin ecosystems. “When we do research in the Alps, for example, we know we are working in places that have been cleared, colonized, and used for agriculture or forestry throughout history,” says Lavorel. “In this remote part of Tierra del Fuego, there has been no human interference. All the physiological traits of the species are directly related to climatic conditions.” The expedition should lead to insights into the evolution and adaptation of species to the harshest climates. And these will provide precious information at a time when climate change is hitting subantarctic regions full on.

Sebastián Escalón

Notes :

1. Laboratoire d'écologie alpine (CNRS / Université Grenoble-I / Université Chambéry).
2. Instituto de Ecología y Biodiversidad, Universidad Católica de Chile.

Contacts :

Sandra Lavorel,
LECA, Grenoble.
sandra.lavorel@ujf-grenoble.fr


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