Pine trees struggle to regrow after severe fires, study finds

New research suggests many California pine groves might have serious trouble bouncing back after a high intensity fire sweeps through an area.

The study, from the University of California, Davis and the U.S. Forest Service, looked at more than a dozen burn sites in the state where pines once grew.

Forty-three percent of the time, those prickly plants weren't sprouting up again five to seven years after a severe fire.

"We figured we weren't going to find regeneration in a relatively high number of plots," said Hugh Safford, a Forest Service ecologist. "I don't think any of us assumed it would be 40 percent or more."

The pine trees seemed to struggle after a large, hot fire for a variety of reasons. Pine trees tend to do better after moderate, slow burning fires since those usually torch the plants on the ground but leave taller trees alive.

Unfortunately, many California forests are overgrown, leading to hotter, faster fires.

These high intensity burns often kill most trees in an area, so there may not be any left to drop seeds.

Safford said another problem is that the seedlings that do emerge are often competing with quicker growing shrubs like whitethorn and deer brush.

These plant species do well after severe fires and cast a lot of shade as they grow. Pines need plenty of sun to thrive.

Recent weather patterns are also working against new pine growth, Safford said: "It’s drier, it’s warmer and the mortality rates are doubtless quite a bit higher."

Climate change will likely amplify these conditions.

The study did offer a ray of hope for pines in California. Nearly 60 percent of plots surveyed showed some regeneration.

Safford and his team also used their research to develop a tool that lets forest managers find the most at-risk pine groves so they can direct restoration efforts to them after a fire.