Post-fire ponderosa pine regeneration with and without planting in Arizona and New Mexico

• Seedling presence increased with number of years since burning.
• Seedling presence was positively associated with forb & litter cover.
• Survival of planted seedlings averaged 25% and ranged between 0% and 70% over sites.
• Half of planted sites are projected to produce desired density of mature trees.
• No unplanted sites are projected to produce desired density of mature trees.

Forest fires are increasing in size and severity globally, yet the roles of natural and artificial regeneration in promoting forest recovery are poorly understood. Post-fire regeneration of ponderosa pine (Pinus ponderosa, Lawson and C. Lawson) in the southwestern U.S. is slow, episodic, and difficult to predict. Planting of ponderosa pine after wildfire may accelerate reforestation, but little is known about survival of plantings and the amount of post-fire natural regeneration. We compared ponderosa pine regeneration between paired planted and unplanted plots at eight sites in Arizona and New Mexico that recently (2002–2005) burned severely. Two sites had no natural regeneration and no survival of planted seedlings. Seedling presence increased with number of years since burning across all plots, was positively associated with forb and litter cover on planted plots, and was positively associated with litter cover on unplanted plots. Survival of planted seedlings, measured five to eight years after planting, averaged 25% (SE = 8) and varied from 0% to 70% across sites resulting in seedling densities of 0–521 trees ha−1. Based on a projected 44% survival of seedlings to mature trees and target density of mature trees determined by historical range of variability and ecological restoration principles, four of eight sites have a seedling density in planted plots (125–240 ha−1) that will produce a density of mature trees (55–106 ha−1) close to desired levels, whereas seedlings are currently deficient at three planted sites, and in surplus at one site, which had abundant natural regeneration. Natural regeneration in unplanted plots during the first decade after burning produced seedling densities inconsistent with desired numbers of mature trees. Natural regeneration in unplanted plots produced less than 33 seedlings ha−1 at seven of eight sites, but produced 1433 seedlings ha−1 at one high-elevation site that supported a more mesic vegetation community before burning than the other sites. Our results show that current practices for planting ponderosa pine after severe fires in Arizona and New Mexico produce desired numbers of seedlings in approximately half of all projects, whereas natural regeneration rarely does within the first decade after burning.