Lichen, an often overlooked organism that forms fuzzy, leaf-like layers over tree bark and rocks, is an unsung hero in forest ecosystems. It provides food for deer, caribou, and elk and is sometimes the only food source for flying squirrels, which are key prey for threatened spotted owls.
Lichen is critical to birds and insects who use it to eat and nest, and lichen communities help restore forest soils by pumping nitrogen in as a nutrient.
For the study, published Thursday in the science journal Global Change Biology, researchers sampled about 100 plots of lichen communities across California’s Sierra Nevada region where five wildfires had burned between 4 and 16 years previously.
Study areas included large patches of the Greater Lake Tahoe Basin burned by the Showers Fire in 2002 and Long Fire in 2009. Areas within Warner Mountains and Yosemite that had burned as far back as 2001, in the Blue Fire, were also studied.
The researchers, from the University of California, Davis, found that lichen communities were largely unaffected by low-severity fires.
“This suggests that prescribed fires and natural wildfires under moderate weather and fuels conditions are compatible with lichen diversity,” researchers said in a statement. “But areas that experienced higher severity wildfires had significantly lower abundance and diversity of lichen.”
In severely burned areas where most of the trees died, nearly all the lichen was gone, even 16 years after the fire.
The lichen’s recovery is likely held back by the loss of tree canopy after the fire, researchers said, adding the communities won’t recolonize until mature trees regrow and the forest canopy is restored.
The study also indicates that the trend of increasingly dry forests and hotter, bigger and more severe wildfires could negatively impact lichen diversity.
A UC Davis study published in 2017 found that crowded stands of trees in the southern Sierra Nevada are the most at risk in the state of dying from extreme drought due to high competition for limited water supplies.
California is going through one of the worst fire seasons on record. The Mendocino Complex Fire burning north of Clear Lake exploded past last year’s Thomas Fire to become the largest fire in state history, scorching more than 304,000 acres as of Thursday morning.
Those conditions could lead to a breakdown in multiple wildlife food chains and deplete forest soils of much needed nutrients, researchers said.
“If the species could keep pace with the rate of climate change, the effects of fire might not be so bad,” said lead author and UC Davis postdoctoral scholar Jesse Miller. “But the concern is they might not. These fires happen so quickly and in such a large area, they could cause species ranges to contract faster than they are expanding,”