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Earth鈥檚 Oldest Trees in Climate-Induced Race up the Tree Line

Bristlecone Pine Trees in Great Basin Are Losing Game of Leapfrog With Limber Pine

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Bristlecone and limber pine trees
Gnarled, dead bristlecone pine trees, which can live more than 5,000 years, stand where young limber pine grow around them. Limber pine is beginning to colonize areas of the Great Basin once dominated by bristlecones. (Brian Smithers/嘿嘿视频)

Quick Summary

  • Tree-line species are shifting in the Great Basin of the United States
  • Limber pine trees are 鈥榣eapfrogging,鈥 slowly, over ancient bristlecone pines upslope
  • If limber pine trees block bristlecones from advancing upslope, bristlecones could face local extirpations

Bristlecone pine and limber pine trees in the Great Basin region are like two very gnarled, old men in a slow-motion race up the mountaintop, and is the starting gun, according to a study from the University of California, Davis.

, shows that the tree line has been steadily moving upslope over the past 50 years in the Great Basin. The region extends from California鈥檚 Sierra Nevada, across Nevada to Utah鈥檚 Uinta Mountains. Its north and south are framed by the Columbia and Colorado rivers鈥 watersheds.

Great Basin map

Charging upslope

鈥淲e are seeing very little regeneration anywhere in bristlecone ranges except in the tree line and, there, limber pine is taking all the good spots,鈥 said the study鈥檚 corresponding author Brian Smithers, a Ph.D. candidate in the Department of Plant Sciences at 嘿嘿视频. 鈥淚t鈥檚 jarring because limber pine is a species you normally see further downslope, not at tree line. So it鈥檚 very odd to see it charging upslope and not see bristlecone charging upslope ahead of limber pine, or at least with it.鈥

Bristlecone pine and limber pine
Dead bristlecone pines stand among limber pine trees on the California side of the White Mountains, part of the Great Basin region. (Brian Smithers/嘿嘿视频)

The study concludes that if bristlecone pine trees are unable to advance upslope because they are blocked by limber pine, bristlecones could face a reduction of their range and possibly local extinctions.

Earth鈥檚 oldest living trees

Bristlecone pine trees are Earth鈥檚 oldest individual trees and can live for more than 5,000 years. No spring chicken, limber pine trees can live 2,000 years or more.

Both tree species have seen many climate changes during their time on Earth 鈥 from extremely warm periods to ice ages 鈥 and have slowly advanced across the landscape. Over millennia, bristlecone pine trees have moved from the lowlands of the Great Basin up to the current tree line. But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.

bristlecone pine on rock ledge
Bristlecone pine trees grow on soils and in conditions where few other species can live. But limber pines in the Great Basin region, such as California鈥檚 White Mountains, are beginning to give them some competition. (Brian Smithers/嘿嘿视频)

Legacy effects

Smithers said he doesn鈥檛 expect bristlecone pine adult trees to be impacted much by current climatic shifts, as those trees are well-established. But how, if and where new bristlecone pine trees will regenerate is less certain, particularly as other species like limber pine take up valuable space for them to germinate.

鈥淭he things we鈥檙e doing today have legacy effects for thousands of years in the Great Basin,鈥 Smithers said. 鈥淲hen those trees do start to die, they won鈥檛 likely be replaced because it鈥檚 just too hot and dry.鈥

The study suggests that land managers identify the specific bottlenecks for a species to live long enough to reproduce, and focus on that stage. For long-lived trees like bristlecone and limber pines, the bottleneck is at the time of their initial establishment, not hundreds and thousands of years into their adulthoods.

The study鈥檚 additional authors include co-leading authors Malcolm North with 嘿嘿视频 and the USDA Forest Service, and Andrew Latimer with 嘿嘿视频, and co-author Constance Millar with the USDA Forest Service.

The study was financially supported by the 嘿嘿视频 Graduate Group in Ecology, White Mountains Research Center, California Native Plant Society, the Henry A. Jastro Fund, Nevada Native Plant Society, and the Davis Botanical Society.

Media Resources

Kat Kerlin, 嘿嘿视频 News and Media Relations, 530-750-9195, kekerlin@ucdavis.edu

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