Discovery and science

What is a cryotron? What is it used for?

You might think it's the name of a species of dinosaur recently discovered in Lautaret, but no... that's not it!

The cryotron is the latest experimental device at the Lautaret garden. It is a prototype created at the request of researchers to simulate and study the consequences of snowless winters in the mountains. Our research support team is proud to announce the deployment of this tool, built with funding from AnaEE France and technical assistance from Ardae, a Grenoble-based company specializing in scientific instrumentation.

High-altitude environments are experiencing the effects of global warming in a very amplified way. These environments are normally covered by snow for a good half of the year. This snow cover plays an essential and structuring role for alpine ecosystems. It insulates them from the freezing temperatures of winter by keeping the ground temperature around 0°C. But with global warming, snowless winters are becoming more common, depriving ecosystems of their protection against low temperatures. The alternating periods of intense freezing and thawing that the soil in the Alps is subjected to will likely disrupt plant and microbial communities, which are not adapted to sub-zero temperatures. The cryotron makes it possible to anticipate and study the effects of reduced snowfall in the mountains.

Construction of the cryotron began in spring 2021, led by Pascal Salze, assistant engineer at the Lautaret garden. Researchers Jérôme Poulenard from the Edytem laboratory (USMB, CNRS), Jean Christophe Clément from the Carrtel laboratory (USMB/INRAE), Philippe Choler from the LECA laboratory (UGA/CNRS/USMB) and Nicolas Bonfanti, their doctoral student (USMB), established the study protocols. The experiment is called Colder soils in a warmer world (Colder soils in a warming world). It involves taking 18 squares of alpine soil at an altitude of 2,000 meters, in "monoliths" measuring 40x40 cm by 30 cm deep, and transplanting them at the same altitude in the cryotron in the Lautaret garden. The cryotron is divided into three 16m² plots.²Six alpine pasture squares were transplanted into each of these plots. The first is equipped with a retractable roof, which closes automatically when sensors detect rain and a temperature below 1.5°C. It is therefore under a "controlled atmosphere." It is a plot where it does not snow. The other two plots are open to the sky. The 12 alpine pasture squares located there will be subject to natural hazards. They are the "controls" of the experiment, which will enable comparative analyses to be carried out.

The alpine pasture disbursements and transplants took place in September 2022, during a training course bringing together master's students in ecology from the Universities of Savoie Mont-Blanc and Grenoble Alpes who are pursuing careers in research. The trainees also installed numerous sensors, with the support of the garden team. Some of these students will participate in the various surveys and laboratory analyses. This experimental platform will enable Nicolas Bonfanti to study how biogeochemical cycles (carbon, nitrogen, and phosphorus) are impacted by the lack of winter snowfall. During 2023, the mineralization rates (activity of soil microorganisms) and primary productivity (plant growth) of the various alpine pasture plots will be analyzed. He will then be able to compare the results between those that have not been covered by snow during the winter, thanks to the cryotron's removable roof, and those that will be covered by snow, as in a "normal" year.

In the context of global warming, it is crucial to understand and observe how plants adapt, the composition of the soil that supports the root system, and the various mineral and organic exchanges that take place. Alpine grasslands are home to a wide variety of biodiversity and are essential to pastoralism. They play an important role in the flow of carbon, nitrogen, and other chemical elements.