The Secret World Of Lichen

A lichenologist’s extraordinary photographs reveal the sublime colours and unexpected configurations of one of earth’s oddest life forms.

Text And Photography By Kevan Berg

I am standing within a curtain of jack pine branches in the boreal forest north of Beardmore, Ontario, a small town northeast of Thunder Bay. It is daybreak, and the sky is flecked with the pink and blue brushstrokes of a crisp June morning. At my fingertips is a species of lichen true to its name, the powdered sunshine lichen, or Vulpicida pinastri. Wrapped tightly on a crooked branch of jack pine, the lichen emits a fierce greenish yellow glow, its lobes ruffled and dissolving into powdery clusters as bright as the sun.

I have been studying and photographing the unique world of lichens for about two years. What I find endlessly fascinating about these organisms is the surprising degree of diversity in size, shape and colour, as well as the tremendously complex coexistence of lichen species in so-called lichen communities. I specialize in lichens that grow on trees, and am interested in the factors responsible for the arrangement and abundance of lichens on conifer branches in the boreal forest. I have discovered that if you look very closely at the branch itself, the entangled lichens bear a striking resemblance to the architecture of the host forest.

On the branch of the jack pine, I can see that V. pinastri is only one of many species rooted down within the peeling bark. Fantastically shaped miniature life forms cover the branch. Fishbone beard lichen (Usnea filipendula) towers above the others, its slender, bone-like tendrils twisting upwards and arching with limbs of ragged beard lichen (Usnea diplotypus). Beneath, the thorny and almost impenetrable gorse-like rampart of burred horsehair lichen (Bryoria furcellata) tumbles across the surface of the branch, a spiny barricade through which the thick spongy stems of boreal oakmoss lichen (Evernia mesomorpha) push skywards. Variable wrinkle lichen (Tuckermannopsis orbata) hunkers down at the centre of the array, lobes tough and leathery. And, not unlike the hidden plants of a forest understorey, hammered shield lichen (Parmelia sulcata) carpets the branch base and fans outwards, enveloping the hollow, hooded lobes of monk’s hood lichen (Hypogymnia physodes).

Another lichen oddity: the branch on which this colourfully tangled congregation occurs is dead. How can something grow without a fertile surface? Lichens are “fungi that have discovered agriculture,” writes lichenologist Trevor Goward. It works like this: A lichen is a partnership between two or more non-plant organisms, one of which is a fungus that acquires water and nutrients from rain and dust. The other half of the partnership is a colony of algae (or sometimes cyanobacteria) that produces food through photosynthesis. In working together, the algae and the fungus create a tiny self-sustaining ecosystem. The fungus is the dominant partner and architect in this relationship, and constitutes the external structure of the lichen within which it shades and protects the algal cells and provides them with water and nutrients. In exchange, the fungus receives a steady supply of sugars and other carbohydrates from its algal partner, sometimes drawing so much that the algae barely survive. The lichen endures only because algae reproduce more quickly than the fungus can starve them – an arrangement that, from the vantage point of the algae, could be characterized as a kind of “controlled parasitism.”

As calamitous as this arrangement may seem, the partnership has been a remarkable success. There are some 14,000 species of lichens worldwide, inhabiting almost every kind of surface and occurring in almost all terrestrial environments. The lichens under scrutiny on the pine branch are classified as epiphytic lichens, meaning that they grow primarily on trees. Epiphytic lichens flourish in Ontario’s boreal forest, a landscape that is wet but cool, and thick with spruce, fir and pine. This unique life form plays an important role in the functioning of the ecosystem. Lichens constitute a significant proportion of the biodiversity of the forest, aid in the cycling of nutrients and provide an abundance of food and habitat for birds, mammals and invertebrates. Certain epiphytic lichens also serve as some of the most sensitive indicators of environmental change in the forest. Due to almost imperceptible rates of growth, as well as fastidious habitat and dispersal requirements, lichens are extremely susceptible to both incremental and sudden changes in their surroundings. For example, clearcutting produces dramatic and instantaneous changes in temperature, moisture, humidity and exposure to light, thereby weakening many lichens growing along the perimeter of a clearcut.

Incremental changes to lichen habitat occur as the forest adjusts to fluctuations in moisture and temperature associated with climate warming. As the range of boreal tree species shifts northward with climate change, lichens specific to these trees will likely decline in health and occurrence if their slow growth and dispersal limit their ability to keep pace with the northward shift of their host trees. Close monitoring of these changes will make lichens increasingly valuable as indicators of the rate and direction of climate change.