Increased whitebark pine (Pinus albicaulis) growth and defense under a warmer and regionally drier climate

IntroductionTree defense characteristics play a crucial role in modulating conifer bark beetle interactions, and there is a growing body of literature investigating factors mediating tree growth and resin-based defenses in conifers. A subset of studies have looked at relationships between tree growth, resin duct morphology and climate; however, these studies are almost exclusively from lower-elevation, moisture-limited systems. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood. MethodsIn this study, we: (1) evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability and (2) determined if tree growth and resin duct morphology of whitebark pine, a high-elevation conifer of management concern, is constrained by climate and/or regional drought conditions. ResultsWe found that high-elevation whitebark pine trees growing in an energy-limited system experienced increased growth and defense under warmer and regionally drier conditions, with climate variables explaining a substantive proportion of variation (similar to 20-31%) in tree diameter growth and resin duct anatomy. DiscussionOur results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high-elevation environments; however, this relationship may change in the future with prolonged warming conditions.

Automated summary

This study evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability in high-elevation whitebark pine trees. The findings suggest that warmer and drier conditions can lead to increased growth and defense in these trees, with climate variables explaining a substantial proportion of variation in tree diameter growth and resin duct anatomy (around 20-31%).