(CN) – A new tool could help foresters determine which forests will regrow naturally after a wildfire and which will need to be replanted manually, while making the process of responding to fires more efficient – crucial for restoration efforts with limited budgets and manpower.
Published Wednesday in the journal Ecosphere, researchers presented a study of 10 national forests and 14 burned areas in California, finding that conifer seedlings were discovered in less than 60 percent of the areas examined five to seven years after a fire.
“High-severity fires are knocking out seed sources and leading to a natural regeneration bottleneck, which poses a predicament for the sustainability of our forests,” said lead author Kevin Welch, a research associate from the University of California, Davis.
The team found that 10 of the 14 burned areas failed to meet the U.S. Forest Service’s stocking-density thresholds for mixed conifer forests, making them ideal candidates for replanting.
“Knowing that the Forest Service doesn’t have the time, budget and staffing levels to restore everything, we basically want to help foresters predict what will be there five to seven years later so they can better focus restoration efforts,” Welch said.
In order to develop a tool for determining how different conifer species respond to a fire and which factors promote or limit natural conifer regeneration, the researchers surveyed a variety of forest types, elevations and fire severities.
After fine-tuning the tool, the team was able to test it against four wildfires that were not reviewed for the study. The tool predicted with more than 70 percent accuracy whether an area would likely need to be restored.
With the tool, an official can enter a forest the year following a fire and use a few simple field measurements – distance to seed source, the cross-sectional area of living trees in the nearby forest, and slope – to predict whether a burned site is likely to meet a desired level of tree density five to seven years later.
The team found that high-severity fires also stimulate regeneration of conifer species that tolerate shade but not fire, including Douglas fir, incense cedar and white fir. The tool could allow foresters to replant species that are more capable of withstanding the warmer, drier climates projected for California.
“As Western forests increasingly experience warmer weather and more frequent and more severe fires, a better understanding of what conifers need to regenerate naturally after a fire can help us create and manage more sustainable, resilient forests,” said co-author Hugh Safford, a regional ecologist for the Forest Service.