Skylar Burg, University of Jyväskylä in Finland, discusses her article: Abiotic conditions along altitude shape plant-fungal associations by influencing both fungal availability and association strength
Setting out in the mountains
High in the mountainous tundra of Norway, Sweden, and Finland, the perennial herb Bistorta vivipara, known as alpine bistort, thrives in conditions that challenge most plants: low temperatures, strong winds, and a brief growing season. Fungal microbes are known to help plants grow in harsh high-altitude conditions, but how these partners are chosen by the plant is unknown. In our recent field study, we investigated the relationship between the local soil fungal communities and the fungi located within different plant parts.
Teaming up with fungi
Alpine bistort is a low-growing plant with slender green leaves, white flowers, and tiny bulbils (little bulb-like baby plantlets). We collected samples of its roots, leaves, and bulbils from many locations above the treeline in tundra environments and below the treeline in valleys. At each site, we also took soil samples and other plants to see what fungi were lurking in the environment.
Back in the lab, we examined fungal DNA from plant tissues (which we called the “selected fungi”) and surrounding soil and plant samples (which we called the “available fungi”) to identify the fungi present. We discovered that the fungi living in the plant’s roots, leaves, and bulbils often reflected the present fungi nearby. In other words, the available pool of soil fungi strongly influenced which fungi turned up inside the plants. This makes sense – plants tend to pick up fungi that are around them.
However, we saw something special at the high-altitude sites. The plants in the alpine zone (above the tree line) seemed to favour certain fungi more than others. In particular, in the highest and coldest spots, we found extra helpful fungi, the kinds known to help plants cope with stress (improving nutrient uptake or helping resist cold). This pattern wasn’t just because those fungi happened to be around, it looked like the plants were actually strengthening their partnerships with those helpful fungi.
Interestingly, the plant’s different parts had different fungal communities. The roots hosted one set of fungi, while the leaves and bulbils had others. A fungus that lived happily in a root might be rare in a leaf, and vice versa. It seems the plant manages its relationships differently in each part of its body.
Life on the edge and what it means
What does this mean? Our study suggests that alpine bistort is not a passive host for fungi. Instead, it seems to play an active role in choosing its microbial allies, especially when conditions get tough. At the highest, coldest sites the plants appeared to strengthen their partnerships with beneficial fungi. In short, the plants may be choosing better allies when they are in more stressful conditions.
This insight fits into a bigger picture of how life endures in extreme environments. The alpine zone (areas above the tree line) is a hard place to grow. Plants there face freezing nights, fierce winds, and a short growing season. By teaming up with the right fungi, they can get extra nutrients and resilience. In fact, many plants rely on fungi called mycorrhizae to help their roots take up water and minerals. Our results hint that alpine bistort is making good use of this kind of partnership.
Understanding these plant-fungal partnerships helps us see the alpine world in a new light. As climates change, the balance of these relationships may shift, too. By knowing that plants can “choose” helpful microbes, we appreciate how adaptable mountain ecosystems are. This story from the Scandinavian peaks reminds us that even tiny plants and fungi are working hard together to keep life thriving high above the valleys.
