Regeneration densities of ponderosa pine decreased with increasing distance to unburned edge. Next, ponderosa pine regeneration could be more strongly influenced by intraspecific facilitation than interspecific competition from dense sprouting species.

The authors found that regeneration in the warmed and dry plots had the lowest growth rates and percent survival of seedlings. The authors suggest that increased temperatures and droughty conditions are likely to inhibit recruitment and seedling survival post-fire or other large-scale, rapid disturbance, potentially leading to new or novel vegetation assemblages.

Fire, drought or other mortality inducing events played a role in initiating regeneration pulses by opening up the canopy and reducing competition. Pluvial events did not trigger regeneration pulses, which were always preceded by fire or drought. Pluvial and quiescence periods enhanced recruitment condition and helped sustain 75% of regeneration pulses.

Areas that had been treated prior to the wildfire had significantly higher ponderosa pine regeneration. The difference between regeneration in treated versus untreated areas was larger for areas burned at high severity. The authors suggest this is due to the greater heterogeneity of patch sizes of high severity fire that were created due to the treatments, allowing for a shorter distance to seed source to facilitate regeneration.

The authors found that large, mixed-severity fires can result in greater heterogeneity of spatial patterns of fire. High-severity patch size varied considerably across both fires in the study. Regeneration also varied considerably within high-severity patches with most seedlings establishing and surviving after 5-10 years post-fire.
Despite subsequent management and other disturbance, including fire, on these study sites, the authors found that the spatial pattern of fire severity was still significantly tied to ponderosa pine regeneration patterns and still impacted the sites decades after the fire. Regenerating seedling density of ponderosa pine decreased with increasing distance to seed source in the high severity patches of fire. Though long-distance dispersal did occur, the rate of recovery was slower with increasing distance to seed source in the larger high-severity patches.

Perennial vegetation in burned areas were able to reestablish to pre-fire levels after approximately 40 years post-fire; however, community composition was slower to recover. Specifically, several species in the Cactaceae family were slowest to recover or absent 40 years after fire and may require centuries to recolonize burned areas. Invasive species colonization or climate change may interfere with community development in the future and a better understanding of post-fire recovery of arid lands is needed.

Cover of woody vegetation that regenerates via seeds were more abundant at shorter distances to unburned edges, which acted as refuge seed sources. However, cover of off-site seeders did not overlap with areas of abundant sprouting species. Pre-fire vegetation composition and structure influenced the post-fire distribution of sprouting species in high-severity burns.

The author found that the stand of ponderosa pine they studied was fairly heterogeneous and did not regenerate in large, even-aged groups following large patches of mortality. They hypothesize that patches of additional fuel surrounding single or small groups of trees likely led to smaller patches of mortality during low-severity surface fires, which would create openings and seedbeds for new seedlings.