Is the air getting too thin for plants?

“Come here, there are loads of them!” Someone shouts from behind a steep slope thirty meters away. We are in the about 1,500 m.a.s.l in the Mazia valley, a small tributary of the Venosta valley and Silvia is on her knees, her hands pointing at the ground. Some isolated larch trees on the sloping meadow and the outlines of a few cows prevent a good view of her, but as soon as she is heard, a sportily dressed group of six get up and move quickly towards her. It may look like it, but no, they are not running to pick blueberries.

Silvia Lembo, a biologist at Eurac Research, has just spotted an expanse of “hairy” clover, her jubilant shouts have caused her six fellow researchers to rush over and help collect the seedlings, pack them up and transfer them to Bolzano, where the second phase of the Upshift project is about to begin. The project investigates the effects of climate-induced plant migration to higher altitudes.
“Hairy clover is a little harder to find, but for our experiment we prefer it to the traditional variety,” explains Lembo as she uses a chisel to pull out a small clod of earth and transfer the seedling with its roots into a perforated black plastic container. “Botanically, the two plants are the same, but the little on this version the hairs form a cover that protect the leaves allowing it to retain more water, making it more resistant.” The team needs several hours to collect 120 clover samples. They crack on diligently, taking just a quick pause to perch on the rocks for a sandwich break.

To complete the sampling, the group needs another species to accompany the clover: 120 specimens of pilosella (Hieracium pilosella), another hairy seedling that has astringent and purifying properties and whose deep yellow flowers could be mistaken for dandelions. “We have to be especially careful to make sure that the plants we choose are not too close to each other otherwise they may have already entered into competition. This means that one of the plants may have grown faster than the other to assert itself,” points out Bouchra El Omari, a biologist and functional ecology expert. “We check that the plants collected all have similar sized leaves; if the samples are too different, observations are less reliable.” El Omari uses something that resembles a big metal cookie cutter to cut into the soil and extract the plant and the surrounding clod in one piece. The holes left must not be too big so as not to disfigure the lawn and are immediately patted back down.

A curious cow approaches the containers already full of clover seedlings. A researcher moves her with a gentle but firm push to avoid her grazing on the carefully collected specimens. The cows and the plants are part of the same ecosystem, any change to one, will affect the other. If the plants change, what will the cows do? And how will the plants adapt to higher elevations?

A few hours later, in the basement of the terraXcube, Eurac Research’s extreme environment simulator, the plants are potted and connected to an irrigation system. One part undergoes a more invasive treatment: researchers break down the soil cake with the roots, wash them under running water and then repot them using soil taken at 2,500 m.a.s.l, 1,000 meters higher than the altitude where the plants lived in the wild. “We do this to best simulate real conditions,” explains Silvia Lembo as she gently buries the fine roots. “The composition of the soil also changes as the altitude changes.”

Each pot is marked with an acronym written in marker pen; each acronym meticulously written on a chart. Then the seedlings are distributed into the four small climatic chambers of the terraXcube, and the doors close.
The climatic parameters set in the chambers are aligned with those measured in nature at monitoring stations at the LTER site operated by Eurac Research in the Mazia valley.

Each plant is given 30ml of water per day, the temperature varies between a minimum of 12 °C to a maximum of 24 °C and light intensity (dark at night and fluctuating between 10 and 85 percent during the day) is kept the same in all the chambers. The only variable: the pressure which simulates that of 260 m.a.s.l ̶ Bolzano’s altitude as well as altitudes of 1,500, 2,500 and 4,000 m, respectively. “The highest simulated altitude is markedly exaggerated, in nature plants will not migrate that high, but we need it to take the plant’s reactions to the extreme to see what happens,” clarifies Bouchra El Omari. “The data we are most interested in is that from the 2,500 m.a.s.l mark, an altitude at which both clover and pilosella are likely to reach in the near future.”

After a week of settling in, measurements begin to assess how the plants have responded to the stress of change. El Omari, Lembo and colleagues, get to work. Using various instruments, they measure how much the leaves have grown, the chlorophyll content, and vapor exchange with the environment. They then carefully insert the data gathered into the excel table.
During the day, plants “breathe in” carbon dioxide and “breathe out” water vapor. The hypothesis is that the lower pressure at high altitude causes the plants to exhale more water vapor, they are more dehydrated, and their growth is impaired.

Last year the working group had already carried out a battery of similar tests, with clover and paléo rupestre (Brachypodium rupestre), a type of grass. “Both species ̶ particularly paleo, have proven to be resilient and hardy. At lower elevations we did not record major changes in any of the altitude parameters except at 4,000 m.a.s.l where we observed a general decrease in biomass. Clover saw a decrease in chlorophyll content in the first two weeks and then recovered in the following weeks at an altitude of 4,000m. ” Lembo says. “However, it is essential to repeat the tests to validate the results, and for the same reason we have placed the plants sampled in the wild, as a control species alongside a greenhouse-grown species: the common Arabidopsis, Arabidopsis thaliana.” And with this Lembo bids us farewell, closing the door of the climate simulator.
Final publication of results is expected by the end of 2024.