Management and natural regeneration in multiple ponderosa pine forests of the southwestern United States

Forest Science
US Forest Service
By: , and 

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Abstract

Management treatments in ponderosa pine forests of the southwestern United States (SWUS) are largely done for wildfire mitigation and restoration to lower tree densities. However, lack of natural ponderosa pine regeneration in undisturbed forests (i.e., no occurrence of stand-replacing events) may require management treatments to promote regeneration. We conducted a field and modeling study in 77 ponderosa pine forests across 7 SWUS locations, with the goal of evaluating management impacts on recent natural regeneration (20 y). We categorized management into 3 broad categories: unmanaged, thinned from above and/or below (thinning), and thinned + understory burned (burning). Although climate suitability declined from 1981-2020, management treatments – especially burning – promoted natural regeneration. High density regeneration, an undesirable outcome, occurred in 21% of managed sites. In addition to effects on near-surface temperature and soil moisture, management conducive to natural regeneration was associated with the density of competing tree species, understory litter and debris cover, and adult tree cone production. Natural regeneration occurred 5-10 y following management, underscoring sustained effects of management treatments on tree reproduction success. Our results show that forest management treatments have the potential to promote natural ponderosa pine regeneration in the SWUS, sometimes at undesirable high densities. Study Implications: Natural ponderosa pine regeneration is declining in forests of the southwestern United States (SWUS), and may increasingly be incorporated as a goal of forest management treatments. Across a diverse set of managed and unmanaged SWUS forest sites, we found that contemporary management treatments – especially thinning + prescribed understory burning – supported natural ponderosa pine regeneration over the past two decades, which were climatically unfavorable in much of the region. Our results show that existing forest management treatments have the potential to promote natural ponderosa pine regeneration in the SWUS, but will require assessment and modification through time to remain effective.

Publication type Article
Publication Subtype Journal Article
Title Management and natural regeneration in multiple ponderosa pine forests of the southwestern United States
Series title Forest Science
DOI 10.1007/s44391-025-00013-z
Volume 71
Publication Date February 25, 2025
Year Published 2025
Language English
Publisher Springer
Contributing office(s) Southwest Biological Science Center
Description 28 p.
First page 203
Last page 230
Additional publication details