Lichens in High Places

What is this life if, full of care, we have no time to stand and stare?

-William Henry Davies

      Often referred to as “nature’s pioneers,” lichens can be found all over the world in places you might have never thought of. While trekking in the mountains have you ever noticed colorful organisms clinging to the rocks? Or while walking through the forest, the branches and twigs scattered throughout the forest floor, covered in green to brown organisms? Most likely, these are lichens. Lichens are a symbiotic association between a fungus and an algae or cyanobacteria (blue-green algae). They play an important role in not only creating beauty in an otherwise dull and lifeless area, they enable other organisms to grow, are a food source, used for nesting material, and can be used to learn about the health of the environment they are in.

      Lichens are the primary colonizers on rocks and trees. The PNW hosts many lichen rich communities including the alpine reaches in the Cascade, Olympic Mountains, and the tree canopies of our temperate rainforests. Being an adventurous group of people, we set out to discover what lichens were hiding under the snowy capped mountains and hanging out in the canopy above our heads.

TREE CANOPIES

      We sat roughly seventy feet high in a Big Leaf Maple tree (Acer macrophyllum) by Little Skookum Inlet, Shelton, WA (Figure 1). We used the Double Rope Technique to safely access the tree and used a cambium saver to protect the tree and rope from abrasion. The majority of life living here were lichens. Organisms require soil for attaching roots to, obtaining nutrients within the soil, and establishing mycorrhizal associations. The bark on a tree is a soil-less substrate that lichens can attach to with their short root-like structures called rhizines. “They are self-sufficient, taking what few minerals they require from the ambient dust (Brodo, 2001),” while also absorbing water and nutrients passing through the canopy. As the tree grows, the first lichens to appear on young twigs and bark are faster growing foliose or fruticose lichens followed by crustose (Brodo, 2001). As you will discover, this is the reverse for lichens colonizing rock.

Figure 1: Foliose lichen Lobaria pulmonaria

      We have climbed in previous trees but didn’t know about the amazing life of lichens hanging out right in front of us. They play several important roles in the canopy such as nesting material and food source for mammals, and most interestingly, some are considered a nitrogen-fixing factory (cyanobacteria). Once the organism dies, it provides nutrients and nitrogen on the substrate that other organisms can then use and thrive on.

      Several mammals rely on lichens for different uses. The arboreal Red Tree Vole (Arborimus longicaudus) makes the high canopy its home, obtaining water from lichens and using them to build their nests. During the winter, lichens are an important food for the Northern Flying Squirrel (Glaucomys sabrinus).

HIGH MOUNTAINS

      At approximately 5,900 feet on Eagles Peak Trail in Mt. Rainier National Park, we were knee high in snow, and facing a bitter cold wind that sent snow biting at our faces. We came here to find some lichens and found beautifully colored crustose lichens attached tightly to a shear faced rock wall (Figure 2). To get here we first started in a low-elevation forest and made our way through the sub-alpine zone (before tree level) where conditions are also cold but trees protect organisms from the elements. We observed lichens along the way and noted a definite gradient as we increased in elevation.

Figure 2: Snow covered crustose lichen.

      Trees tend to shrink while other plants disappear entirely. Lichen strategies change as body mass is reduced and soon only crustose lichens prevail. They endure several stressors including a short growing season, relatively high proportions of UV light, cold/heat, abundance/lack of water, nutrient deficiencies (especially nitrogen), heavy metal excess, low O2 and CO2 pressures, wind, snow, and ice (Trappe, 1988). Yet, with all of these challenges, they have adapted and are able to thrive where others cannot.

      Living in these extreme environments is an amazing concept and one that is the most important. They are the first to colonize bare rock and with their root-like structures called hyphae, they weave their way into minute cracks in the rock. Through temperature expansion and contraction, the rocks slowly break down. During this process their tightly compressed body structures capture minute particles and dust. Over time, this provides nutrients and soil that other organisms can establish on. There is extensive research on the North American Caribou (Rangifer tarandus) whose winter diet solely relies on lichens. Another fan of eating lichens are mountain goats (Oreamnos Americanus).

STAND AND STARE

      The next time you’re out climbing mountains and/or trees take a while to stand (or hang in the air) and stare at natures most interesting pioneers. Envision them coming in and slowly changing and contributing to the community around them. In comparison, the succession of lichens in either the canopy or high mountains are opposite because of their adaptations. Crustose lichens can withstand stressors that foliose and fruticose lichens cannot. But with their rhizines and largely lobed bodies, foliose lichens have the advantage in the canopy. They over compete with the slower growing crustose. In an old-growth forest and alpine habitat, the lichen can be as old as the tree or rock has been there! Especially in the PNW remember to use a cambium saver when tree climbing to reduce your impact. When climbing in the mountains try walking on the snow instead of crustose communities on the rocks.

      Now that you are aware and have learned about lichens in high places we hope you will continue to educate yourself. We only touched briefly on the importance of lichens including how they provide suitable habitat for others, nesting material and food for mammals, increase biodiversity, fix-nitrogen for other organisms to use, and they are just down right dazzling! Some other areas of interest are lichens as bio-indicators (sensitivity to air pollution), used for perfume, dyeing, and traditional medicine. You can help protect and conserve them by remembering that every footprint leaves a mark, so tread lightly.

REFERENCES
Chapter in a book: Brodo, Irwin. 2001. Lichens of North America. Yale University Press.

Book: Geiser, Linda and McCune, Bruce. 2009. Macrolichens of the Pacific Northwest. Oregon State Universtiy Press. Corvallis, Oregon.

Journal article: J.M. Trappe. Lessons from Alpine Fungi. 1988. Mycologia 80:1.

Journal article: Peterson and McCune. The Importance of Hotspots for Lichen Diversity in Forests of Western Oregon. 2003. The Bryologist 106(2):246-256.

Journal article: Sillett, McCune, Peck, and Rambo. 2000. Four Years of Epiphytic Colonization in Douglas-fir Forest Canopies. The Bryologist 103(4):661-669.

THANKS
To my wonderful group members.

Zachary Alexander

Bryce Limon

Sam Kaviar

me!

Our project video made by Zach