Lichens Slow to Return After Wildfire

Frequent Fire Narrows Recovery Window for Lichens in Chaparral Shrublands

by Kat Kerlin
May 10, 2021

old-growth lichen attached to branches — Old-growth lichens, including Usnea spp., Flavoparmelia caperata, Evernia prunastri, Parmelina coleae., and Parmelia sp., attach themselves to a tree branch at the Quail Ridge Reserve. A �鶹��ý study highlights the value of old-growth chaparral systems to local biodiversity. (Jesse Miller)

Lichen communities may take decades — and in some cases up to a century — to fully return to chaparral ecosystems after wildfire, finds a study from the University of California, Davis, and Stanford University.

, published today in the journal Diversity and Distributions, is the most comprehensive to date of long-term lichen recolonization after fire.

Unlike conifer forests, chaparral systems in California are historically adapted to high-intensity fires — they burn hot, fast and tend to regenerate quickly. However, with more frequent fires predicted under a drier, warming climate and more ignitions occurring amid a growing human population in these areas, the study indicates that lichen communities may not receive the window of opportunity they need to return to chaparral shrublands after wildfire.

“In chaparral systems, lichens can come back 20 to 30 years after fire, but if you get into more frequent burning several times in a short time period, it may be there isn’t a place for these lichens,” said co-leading author Alexandra Weill, who conducted the research while a graduate student researcher in the �鶹��ý Department of Plant Sciences.

Post-fire landscape in chaparral shrub land, Quail Ridge, California — Quail Ridge Reserve following a 2020 wildfire. The barren patches were formerly chaparral that burned at high severity. (Jesse Miller)

Overlooked and all around

Lichens are complex organisms born from a symbiosis of fungi and algae. Overlooked and yet all around, they present a variety of colorful and intricate shapes and patterns along the rocks, branches and floor of forests and other biomes. They not only provide food for wildlife, they also help retain moisture in their environments — an increasingly important service in dry chaparral systems.

“There’s also value to biodiversity itself,” said co-leading author Jesse Miller, a �鶹��ý postdoctoral researcher at the time of the study and currently a lecturer at Stanford. “In our study, plant diversity was low under the dense shrub canopy. But we could find dozens of lichen species in the same area. If we lose these lichens, we’re losing a lot of the actual biodiversity that’s there.”

lichen attached to tree branch — Lichen attach to a branch at �鶹��ý’ Quail Ridge Reserve. A �鶹��ý study finds it can take lichens 20 to 30 years to recolonize an area after wildfire. (Alexandra Weill)

Not ‘lichen’ frequent fire

To test how lichens recolonized in chaparral systems after fire, the scientists in 2018 sampled lichen communities at two �鶹��ý natural reserves — and nearby in Napa and Solano counties. Using records from CAL FIRE and Quail Ridge Reserve, they i