Comparative species assessments of five-needle pines throughout the western United States

• Published in: Forest ecology and management 2021-09, Vol.496, p.119438, Article 119438
• Main Authors: Goeking, Sara A., Windmuller-Campione, Marcella A.
• Format: Article
• Language: English
• Subjects: Forest inventory; Foxtail; Great Basin bristlecone; Limber; Pinus albicaulis; Pinus aristata; Pinus balfouriana; Pinus flexilis; Pinus longaeva; Pinus strobiformis; Rocky Mountain bristlecone pine; Southwestern white; Whitebark
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2021.119438

•Forest inventory data provide broad-scale assessments of species of interest.•Whitebark and limber pine mortality has occurred faster than growth of live trees.•Most five-needle white pines exhibit a reverse-exponential size-class distribution.•Regeneration of five-needle white pines is abundant in non-white pine forest types.•Great Basin bristlecone and foxtail pine populations have few sapling-sized trees. Five-needle white pine species provide important ecosystem services throughout the western U.S., and many of these species have become susceptible to stressors including warmer temperatures, insect epidemics, nonnative disease, and altered disturbance regimes. The objective of this study was to characterize recent broad-scale demographic patterns, including species abundance (i.e., numbers of individuals, tree density, size-class distributions, recruitment, growth rates, mortality rates, and causes of mortality, for the six species of five-needle pine that occur in the western US. We used the U.S. Forest Service’s Forest Inventory and Analysis (FIA) dataset, spanning greater than 10 years, to quantify demographic status and trends for each species. FIA data were compiled from a probabilistic sample design and consistent analysis framework that included not only the dominant community types of five-needle pines, but also all other forest community types, which have previously been demonstrated to encompass abundant regeneration of five-needle pine species. Our analysis revealed similar trends for whitebark and limber pines: both species exhibited increased levels of mortality that are occurring faster than growth of surviving trees, as well as abundant regeneration in forest types that are not dominated by five-needle pines. Although limber pine has experienced lower mortality rates than whitebark pine, it nonetheless showed signs of decline that are comparable to broad-scale indicators exhibited by whitebark pine 10 years prior. In contrast to whitebark and limber pines, Great Basin bristlecone and foxtail pine mortality rates were relatively low, and their populations exhibited a flat diameter distribution except for restricted recruitment from seedling to sapling size-classes. Our findings suggest that five-needle white pine species would benefit not only from increased seedling recruitment, but also from enhanced recruitment among older and larger age and size classes. Thus, it may be important to apply a variety of management strategies – includin