Plants that teach us to care for one another in hard times

A study published in the journal Polar Biology (Springer) reveals how a cushion-shaped plant called Bolax gummifera helps other species survive the extreme conditions of southern Chile. The study is co-led by our director of learning, biologist and Doctor of Education, Manuela Méndez*.

On the peaks of Isla Navarino, where Puerto Williams is located, conditions for plants are especially harsh: strong gusts of wind, below-freezing temperatures for much of the year, unstable terrain, and snow cover that persists for more than 200 days. In this extreme environment, some plants help others survive.

A study carried out on the island during the summer of 2011 examined how different species of plants and mosses relate to the dense, protective cushions formed by Bolax gummifera. These structures can create more favorable conditions for other species, acting as small “shelters” against the harshness of the environment.

The study, titled Spatial associations of vascular plants and mosses with Bolax gummifera cushions in sub-Antarctic alpine habitats: are they similar?, compares the presence of both plant groups inside and outside these cushions to understand how they interact within the same community.

The research was co-led by Manuela Méndez, a biologist specializing in ecology and education, together with researchers from the Sub-Antarctic Biocultural Conservation Program (1), the Cape Horn International Center (CHIC), and the Institute of Ecology and Biodiversity (IEB), and offers new insight into how plants form supportive relationships in some of the harshest environments in the southern hemisphere.

A shelter plant

In ecology, there is a concept called facilitation, which describes relationships in which one species promotes the survival, growth, or reproduction of another. In this case, Bolax gummifera acts as a “nurse plant,” since its particular growth form creates a shelter that helps other species better withstand extreme conditions.

On Cerro Bandera, on Isla Navarino, this small plant forms compact cushions up to 135 centimeters in diameter. Covered in star-shaped hairs and a resin that turns reddish as it dries, it plays an important role in the plant communities above the treeline. Its cushion acts as a multifunctional shelter: it buffers extreme temperatures, retains moisture in a dry environment, stabilizes the terrain, and traps sediment that enriches the soil. In this way, Bolax not only finds a way to survive in adverse conditions, but also creates an environment favorable for other species to do the same.

For Manuela, discovering these relationships was an experience of “inter-species co-learning.” The mountains have been an important part of her life: for years she has hiked and climbed its routes, experiencing firsthand the importance of sharing and supporting one another in these environments. “In climbing and on glaciers, for example, people stay roped together to protect each other from falls,” she notes. Carrying out this study was, for her, a way of recognizing that something similar happens among plants.

This research changed the way she saw a landscape she thought she knew. She discovered, for example, that in places that seem to be dominated by rock and ice, there were far more forms of life than expected: plants, mosses, lichens, and other “discreet, subtle presences” that can only be seen by stopping, crouching down, and shifting perspective. When we walk a trail, we tend to look toward the grand landscape and its vastness, explains our director of learning. The study, however, led her to focus instead on what happens just centimeters from the ground. There, she found spatial patterns showing a tendency among different species to cluster and live together.
To better understand this phenomenon, the research team (2) wanted to observe whether vascular plants (with roots, leaves, and stems) and mosses (with simpler structures) respond to Bolax gummifera cushions in the same way. The comparison arose, Manuela says, out of “curiosity, intuition, and fairness toward the mosses,” since in the sub-Antarctic ecoregion they are more numerous and diverse than vascular plants and have different strategies for coping with extreme conditions. In fact, they can absorb water directly from the environment and withstand long periods without it. Mosses are, in a sense, tougher. “They’re very patient. They know how to wait, to slow down their activity and energy expenditure when conditions are hard, and to reactivate when there’s a bit of water and start their metabolic activity again. Mosses often look dead, or seem to disappear from view on very dry days, but then a few drops fall and they come back to life,” Manuela explains.

Two slopes

The study analyzed the relationship between Bolax gummifera, mosses, and vascular plants on two slopes of Cerro Bandera with different climatic conditions. The equator-facing slope received more solar radiation but was more exposed to wind, water scarcity, and extreme temperature swings. The pole-facing slope was colder, but held onto snow and moisture longer and was more sheltered from the wind.

As Manuela points out, wind plays an especially important role in this balance: “Anyone who has traveled through the Magallanes region has felt those winds while walking, has seen trees shaped by the wind as they grow; and that wind is so significant that it affects the availability of water and snow. We often think of snow as something that makes life harder, but it can act as a protective cover, the same way igloos help Arctic peoples: a layer of snow also shields against wind and other fluctuations.”

On each slope, the team studied 50 Bolax cushions, recording the vascular species growing inside them and in nearby areas of bare ground. Mosses were collected and identified afterward. Variables such as temperature, humidity, and degree-days (an indicator used to estimate the accumulation of temperatures favorable for plant growth over the season) were also measured. Vascular plants showed a strong association with Bolax cushions. On the equator-facing slope, where conditions were harsher, 70% of vascular plants were found inside them. The Relative Interaction Index (RII), used to measure the relationship between Bolax and other species, reached 0.80 on this slope, compared with 0.52 on the pole-facing slope. For mosses, by contrast, values were close to zero on both slopes of the mountain: 0.21 and −0.10. This means that, as a group, there is no significant association between mosses and the cushions.

One notable point was the difference between the two slopes: the relationship between Bolax and vascular plants was strongest precisely where conditions were most difficult.

These results are consistent with the Stress Gradient Hypothesis (SGH), which holds that as environmental conditions become harsher, supportive relationships between species can become more important for survival. In this case, Bolax appears to offer exactly that extra support: a space where other plants find conditions that would be harder to reach outside the cushion.

“In these places, the presence of a species like Bolax gummifera is key. Many of the species found on the slope only grow inside this plant (which is like an island in the middle of the sea), which provides them with the right conditions. In that sense, sharing space and living together is linked to greater richness, in ecological terms. It’s a beautiful thing, and you can even read about it in the work of naturalist Edmundo Pisano (3), whose accounts describe these mats and their diversity wherever cushion plants are found,” the scientist and educator reflected.

Living thanks to a web of life

Beyond Navarino, the research shows that environments that seem inhospitable at first glance can hold diverse communities and complex ecological relationships. The species recorded on Cerro Bandera do not exist in isolation: they are part of a web of relationships in which the conditions created by some species can influence the survival chances of others.

For Manuela, this discovery changed the way she sees the world, inviting her to inhabit it with greater gratitude and humility. “Understanding yourself as small, and completely dependent on other beings and their interactions in order to live, is a wonderful thing,” she reflects.

Her life exists thanks to a complex web of relationships: plants, cyanobacteria, and algae, with their photosynthetic wisdom, transform the sun’s energy into molecules that give us energy and build our bodies, along with the oxygen that lets us breathe. Ecology, she notes, helps us understand patterns and processes, and think through the life and biotic interactions that allow life to exist on this planet. “No one lives alone, no one survives alone, and every human relationship is bound up with nature. Interdependence means that we are nature,” she says.

Footnotes

(1) The Sub-Antarctic Biocultural Conservation Program is a transdisciplinary initiative founded more than 20 years ago that brings together ecological science and environmental ethics to protect biodiversity at the southern tip of South America.
(2) The work was carried out by a multidisciplinary team made up of Manuela Méndez (FMA), Ricardo Rozzi (Sub-Antarctic Biocultural Conservation Program, University of North Texas, and CHIC / Universidad de Magallanes), Juan Larraín (Centro de Investigación en Recursos Naturales y Sustentabilidad, CIRENYS, Universidad Bernardo O’Higgins), and Lohengrin A. Cavieres (Universidad de Concepción and IEB). The study also received field support from Kimberly Mighell and collaboration from Roberto Rodríguez and Alicia Marticorena (curator of the herbarium at Universidad de Concepción) in the taxonomic identification of the vascular plant species.
(3) Edmundo Pisano (1919–1997), an agricultural engineer and botanist from Punta Arenas, devoted his life to studying the flora and vegetation of Chile, particularly the Magallanes region.

*Manuela Méndez Herranz. Director of Learning, FMA. Biologist with a specialization in environmental studies, Master’s in Science, Master’s in Education, and Doctor of Education from the Pontificia Universidad Católica de Chile. Her research focuses on the intersections of ecology, education, and biocultural conservation.