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

Abstract

a b s t r a c tForest 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)(2003)(2004)(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 À1 . 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 À1 ) that will produce a density of mature trees (55-106 ha À1 ) 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 À1 at seven of eight sites, but produced 1433 seedlings ha À1 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.Published by Elsevier B.V.

Limited conifer regeneration following wildfires in dry ponderosa pine forests of the Colorado Front Range

“…In a recent study of high‐severity burn areas of Arizona and New Mexico, seedling survival was only 0–12% in three of the eight burns (Ouzts et al. ). This suggests that, consistent with our findings, seed availability is not the sole cause of limited tree regeneration.…”

“…, Dodson and Root , Ouzts et al. ). More research is needed to determine whether limited post‐fire conifer regeneration is a widespread phenomenon in the western United States, and whether climate change, increased fire severity, limited time since fire, or a combination of these and other factors explain observed patterns.…”

“…In the western Unites States, concern has grown among researchers and land managers that recently burned landscapes may be exhibiting lower resiliency to fire. Grasslands or shrublands now dominate in some previously forested areas, at least in portions of burns where seed availability is low (Savage and Mast 2005, Keyser et al 2008, Roccaforte et al 2012, Dodson and Root 2013, Ouzts et al 2015. More research is needed to determine whether limited post-fire conifer regeneration is a widespread phenomenon in the western United States, and whether climate change, increased fire severity, limited time since fire, or a combination of these and other factors explain observed patterns.…”

The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States

“…Recruitment failures and conversion to shrublands or grasslands are common following recent high‐severity fires in the southwest (Roccaforte et al ., ; Savage et al ., ). The use of artificial regeneration (planting or direct seeding) offers a potential solution to some of the recruitment failures that have arisen following catastrophic fires and the loss of local seed sources (e.g., Haire & McGarigal, ; Zhang et al ., ; Feddema et al ., ; Ouzts et al ., ). However, planting must be done to match seedling genotypes and species for given locations (e.g., Blazier et al ., ; Will et al ., ), especially if done in the midst of a long‐term or deepening drought.…”

Anticipating fire‐mediated impacts of climate change using a demographic framework

“…In contrast, 16 years after the La Mesa Fire in New Mexico, cover of naturally regenerating ponderosa pine in plots adjacent to a live seed source was less than one per cent (Foxx et al., ). Even where ponderosa pine seedlings were planted postfire, the average seedling survival 5–8 years after planting was only 25% (Ouzts, Kolb, Huffman, & Meador, ), highlighting the potential climate limitations to ponderosa pine recruitment. Thus, fire‐mediated impacts of climate warming in the south‐west United States highlight the interaction between altered fire behaviour (e.g., crown fires) and an increased frequency of postfire drought that leads to shifts from forest to shrub‐ or grass‐dominated systems (Feddema et al., ; Seager & Vecchi, ).…”