Ponderosa pines are not adapted to high-severity fire

And this type of fire is increasingly common in the Southwest

Regenerating Ponderosa Pine
Regenerating ponderosa pine in a high-severity burn patch, 13 years after the 2000 Pumpkin Fire. (From the Fact Sheet)

The increasing size and severity of wildfires in the Western United States may have long term effects on species composition. A Fact Sheet published this month by Northern Arizona University and the U.S. Forest Service looks at ponderosa pine regeneration in patches of high-severity areas of the 2000 Pumpkin and the 2002 Rodeo-Chediski wildfires in the Southwest. Below are excerpts from the document written by Suzanne Owen, PhD student, School of Forestry, Northern Arizona University:


Over the past three decades, wildfires in southwestern U.S. ponderosa pine (Pinus ponderosa) forests have increased in size and severity, leaving large, contiguous patches of tree mortality. Ponderosa pines evolved under fire regimes dominated by low- to moderate-severity wildfires. They are poorly adapted to regenerate in large patches of high-severity fire because they are not a sprouting species and do not have serotinous cones or long-lived soil seedbanks. Consequently, the lack of seed-producing trees in high-severity burn patches may prevent or significantly delay ponderosa pine regeneration. Previous studies have documented low ponderosa pine regeneration densities in large high-severity burn patches, but less is known about the spatial patterns of ponderosa pine regeneration and interactions with sprouting species near residual live forest edges or the interiors of high-severity burn patches.



  • Ponderosa pines were re-establishing in all of our study plots, however regeneration densities were lower farther from forest edges.
  • Ponderosa pines seedlings were found in areas more than 980 feet from potential parent trees on all interior study plots.
  • Regenerating ponderosa pines displayed patterns of small-scale spatial aggregation in all plots, except one edge and one interior plot on the Pumpkin Fire, which displayed random distributions.
  • Dense resprouting trees dominated tree regeneration on the Rodeo-Chediski Fire, but did not influence the spatial location or height of regenerating ponderosa pine.
  • Regenerating ponderosa pine height was positively correlated with neighboring ponderosa pine densities and height.


  • Tree regeneration densities and species composition in high-severity burn patches are highly variable in different geographic locations.
  • Regeneration patterns suggest both short- and long-distance dispersal may play important roles in ponderosa pine regeneration in high-severity burn patches.
  • Ponderosa pine regeneration could be more strongly influenced by intraspecific facilitation than interspecific competition from dense sprouting species.
  • Future forest spatial patterns and composition are still unclear, but at this stage of development, these heterogeneous patches, characterized by drought-tolerant sprouting species or low pine densities, could be more resilient to climate change and severe wildfires than the overly dense ponderosa pine forests that were present before the wildfires.
  • Managers may want to use a “wait and see” approach before replanting in some areas to monitor natural regeneration over time.

Climbing trees to harvest pine cones after the Wallow Fire in Arizona

Wallow Fire
Engine crew works on the Wallow Fire in 2011. Photo by Jayson Coil.

On a recent October day south and west of Alpine, AZ, James Nesslage and Brandon Billy were harvesting a bumper crop of cones from the top branches of a 100-foot tall ponderosa pine. That tree and others like it are survivors of the 538,049-acre Wallow Fire that burned in eastern Arizona and western New Mexico in 2011, most of it within the Apache-Sitgreaves National Forest. The cones being picked will yield the seeds needed to continue the restoration of parts of that vast burn.

picking pine cones
James Nesslage climbs a rope rigged in a 100-foot ponderosa pine tree as as he and his crew prepare to harvest seed cones on the Apache-Sitgreaves National Forest southwest of Alpine, AZ. Photo by Tom Story.

Plans to restore the forest began before the Wallow Fire was contained. Initial estimates were that high burn severity over much of the fire area would result in natural regeneration being hampered by a lack of available seed trees.

To have the best chance of survival, seedlings must be grown from cones taken from parent trees in the area. Patrick Murphy, silviculturist on the Apache-Sitgreaves, explained:

Several factors are used in determining where cones are harvested and from which trees seed is collected.  The forest has pre-established “seed zones”.  These seed zones are geographic locations found throughout the forest.  In collecting seed we take into consideration if the parent tree is free from insects, disease, defects, deformity, or forking.  The tree should also exhibit superior height and diameter growth.  We will plant seedlings in the same seed zone and elevation band where the parent tree is located.

Earlier in the year, there was a larger crew of 20 people harvesting the seed cones. Now as the cone picking season, which began in mid-August, was winding down, there were only two other people; father and son Randy and Brandon James, working that day.  It would take two to three hours for each team to completely strip the tree of its cones. “The contract specifies eighty-percent (of the cones on each tree)” said Mr. Nesslage, “but we try to do better than that”. The pine that the James duo picked that morning barely produced a bushel of good cones while the tree that Mr. Nesslage and Mr. Billy harvested yielded over three bushels.

picking pine cones
Brandon Billy works his way out on a limb as James Nesslage (mostly hidden at right) uses a hook to pull the cone laden tip of a limb close to Mr. Billy during the seed cone harvest. Photo by Tom Story.

A general contractor in the construction business, Mr. Nesslage came across a solicitation for a seed cone harvesting contract on the Federal Business Opportunities website and thought it was a chance to put some of his climbing experience to good use. “Go camping, climb trees and get paid for it! Sweet!” was his reaction. He was awarded a contract and started picking in 2012.  He admitted that the learning curve was a little steep at first but was able to complete the harvest. The cone crop in 2013 was poor and was not picked, so when Mr. Nesslage’s teams returned to the woods this year, not only was there more to harvest, they had a larger crew and more knowledge of how to do the job better and more efficiently.

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