Lichens play an important role in Newfoundland and Labrador’s approximately 38 million hectares of boreal forest.
Since moving to the province to begin a master’s degree in biology under the supervision of Dr. Yolanda Wiersma, Rachel Wigle has been involved in a number of rare lichen projects.
Indicators of environmental change
“About 10 per cent of the biodiversity in the boreal forest is lichen,” said Ms. Wigle.
“Here, they contribute to the environment in a variety of ways. In winter, when many organisms go dormant, certain lichen species actually increase their photosynthesis because, without leaves on the trees, there is much more light available to them.”
She says caribou eat lichen in the winter and it’s a year-round food source and habitat resource for many other mammals and insects.
“If there is a disturbed habitat, lichens are some of the first organisms to come in and start breaking down the old material to make new soil, acting as ecosystem pioneers, getting the environment ready for the next organisms to come along,” she said.
Ms. Wigle thinks people don’t pay much attention to lichens because they grow very slowly — even though they do a lot of heavy lifting when it comes to being great indicators of environmental change.
“If there is pollution, certain species will die off, but others love it,” she said.
“In Bannerman Park [in St. John’s], for example, there are species of lichen you won’t find in the forest, because they actually like pollutants. When pollution increases, they grow more and produce more oxygen. They could have an amazing ability to mitigate pollution, but we haven’t determined how to harness it yet.”
Ms. Wigle’s research has taken her all around the Central Avalon region, investigating lichen communities on trees — their abundance, how much of a tree they cover and identifying the different species that can be found. Some microspecies are so small, they look like tiny paint splatters.
Ms. Wigle also took note of the characteristics of the forests lichen were found in, including tree height, canopy cover, density and the site slope and aspect. She also recorded information about the trees that were home to lichen, measuring the barkpH and size and even taking straw-size cores in order to count the growth rings.
“That’s when I realized the yellow birch trees were very old — some over 200 years old — while most of the balsam firs were, on average, 40 years old,” she said.
She also noted a stark contrast in lichen found on yellow birch trees compared to the more common balsam fir.
She says a tree is like “a little island” for lichen. The type of “island” it is will dictate what species will be found there. Lichen on balsam fir and black spruce trees are comparable, whereas yellow birch is a whole other habitat.
“Since balsam fir and black spruce are so common, those lichen are everywhere,” Ms. Wigle said.
“But yellow birch is rare, and so are the lichen species that make the yellow birch its home. White birch is different because it’s constantly shedding its bark, so those lichen can only grow for a short period of time.”
After spending half a summer looking for yellow birch from data provided by the provincial government, sometimes taking an entire day to get to a site, she found that many of the tree stands contained merely the remnant stumps of large yellow birch trees.
“That happened a few times, and at those sites you could see balsam fir starting to creep in,” she said. “Yellow birch can’t compete with balsam fir for two main reasons: the balsam fir grows faster and the yellow birch represent a better food option for moose. Old trees are being cut down and moose are eating all the young growth — so the population is being cut from both sides.
“Once they’re gone, they’re gone,” she added. “I don’t think they will come back naturally. It’s sad because we could be losing rare species of lichen, that 10 per cent of the biodiversity in these forests, and without more research, we don’t know what value they could be adding to the ecosystem.”