Elise Grange
Vascular plants, and fungal communities are experiencing big changes in alpine areas around the world. While the effects of warming temperatures in alpine zones has been documented in regards to vascular plants, little has been said on one of the region’s most common organisms, lichens! Lichens are a type of fungal organism that consists of a hard fungal “shell” and green algae, if you’ve been to an older forest and seen what looks like green hair hanging from a branch, or an odd looking crust on a rock, or on a tree, it was probably a lichen. Lichens odd and interesting shape is the result of a relationship between a fungi and a photosynthetic symbiont (in layman’s terms, a mushroom and a plant)
Alpine environments are a rare and fragile place that are a diversity hotspot for vascular plants, fungi, and animals that are situated on high mountaintops. The cold frigid temperatures, and high altitude means living organisms need to use every tool in their belts to survive. What’s notable about alpine zones is their lack of trees. These areas don’t exactly exclude trees through a fancy system; they are just so hostile that trees physically cannot grow in them. Climate change and warming have had huge effects on these regions by shifting the areas of livable and suitable conditions. So, when an area on a mountain becomes much warmer, in turn organisms that were once unable to live there, suddenly can. This is an issue because the plants in alpine areas need as much sun, and as much moisture as they can get so they can survive, and any limitation has major effects on their survival.
A study from northern Sweden that lasted 18 years has taken up the task of studying the effects warming has on a variety of lichen species. This was done by creating 1 x 1 meter plots that had uniform vegetation in meadows, and heathland plant communities. 12 plots were created in each plant community with 8 being control plots and 4 being “warmed” plots. How was warming done to see the impact of temperature increase? Researchers fitted 4 plots with open top chambers (if you look them up they are the little silver hexagon type things with the tops cut off) which increased the air temperature by 1.5 to 3 ℃. With this, researchers could compare plots that were in a simulated warmer climate that may be similar to what the future will look like for alpine environments. These open top chambers were left on year round, and were assessed several times over the 18 year study by counting coverage in the plot during peak growing seasons.
The results of the research showed that in control plots for heathland and meadow plots, there was more lichen cover, richness, total species, and evenness than the warming plots had, which experienced major decreases in all categories. The difference between the two however, was that cover of lichens increased by 87% in heath control plots, but only by 21% in meadow control plots. With warming plots, lichen cover decreased by 8% in heathland , and by 31% in meadows. What does this mean? Firstly, warming is bad for lichens in both communities and particularly bad in meadows. The reasoning given by researchers is that meadow communities have much more canopy cover than the heathland communities do. The heathlands are only composed of small shrubs, but the meadows contain tall alpine grasses that overshadow the lichens, preventing them from getting the moisture and sunlight they need. Over the long period of warming, plant canopies also increased, which coincided with several other studies showing that warmer temperatures results in denser vascular plant canopies. This unfortunately means, while vascular plants will benefit from warmer temperatures in alpine areas, it seems lichens will get the short end of stick, losing more of the sunlight and moisture that sustains them. Alpine areas host a large amount of unique endemic lichens that can’t be found in other ecosystems, and it seems that warming temperatures may cause them to go extinct.
While this study was done in Sweden, if you’re interested in what alpine ecosystems look like in the United States the book Land Above the Trees: A Guide to American Alpine Tundra by Ann H. Zwinger and Beatrice E. Willard has a lot of wonderful line drawings and plant community explanations that give context on the functionality of this unique ecosystem.
