Some Ponderosa Pine Forests Naturally Regenerate after Wildfire Management Treatment

Spanning from the Black Hills of South Dakota to the California Coast, ponderosa pines have the broadest range of any North American pine species. However, their future growth is becoming increasingly uncertain as they struggle to regenerate naturally after high-intensity wildfires. 

To mitigate wildfire and restore forests to lower tree densities, resource managers in the Southwest U.S. have turned to various understory-reducing management techniques. These typically include thinning small trees, clearing out dead material and prescribing controlled surface burns. While these methods have been effective for wildfire mitigation, it is unclear how the treatments promote natural forest regeneration. 

In a recent publication in Forest Science, research funded in part by the SW CASC shows that these forest management treatments have widely supported the natural regeneration of ponderosa pine forests over the past twenty years, despite unfavorable climatic conditions. 

Researchers communicated with local forest managers at seven regional locations in the Southwest to identify ponderosa pine-dominated forests with varying levels of historic management. They used field observations, meteorological estimates and water balance modeling to compare the impacts of drought and increased temperature with management treatments in shaping natural regrowth. The researchers found that treatments like understory thinning and burning supported the ability of new trees to grow by reducing competition from other plant species, changing forest structure and improving environmental conditions. Though, in some cases (21% of managed sites), forests regenerated at an unfavorable high density and in others there was little regeneration at all, implying that follow-up treatments may be needed. With continued assessment and modification through time, management strategies can help ponderosa pine forests continue to take root across their expansive geographic range.

Read the full publication in Forest Science.