The plants growing back after this generation of wildfires in northern California are species that usually grow in southern California or Mexico -- that's according to a new UC Davis study.
Fire suppression has left forests vulnerable to larger fires. Today's flames are scorching both the understory and the canopy.
"You've taken the roof off, and so the sun beats through a lot hotter," says lead author Jens Stevens, a postdoctoral scholar with the UC Davis John Muir Institute of the Environment. "And the more severe the fire is, the more canopy you lose after the fire, the bigger the change was."
Stevens says more heat resistant plants like manzanita or monkey flower are replacing lupine and violets. The new plants were already there -- just in smaller numbers around the edges of a forest, or in an opening. But, when the canopy disappears southern species become much more common.
Stevens says the trend demonstrates why forest managers need to thin trees so fires don't burn as hot and destroy the canopy. These forests burned less hot and, therefore, left some tree canopy, allowing for both northern and southern plant species to coexist.
"If we can create conditions that have a diversity of habitats then we can get a diversity of species," says Stevens. "And, having a diversity of understory plant species, for example, can provide a wider base of food resources for wildlife species, and can maintain genetic diversity for the species that are present."
The study, published in the Journal of Ecology, examined 12 different mixed-conifer sites in California stretching from Modoc to San Bernardino counties. It included several sites in the Sierra, including forests burned by the Angora Fire in 2007 and the American River Complex fires that burned northeast of Sacramento in 2008.