Washington, November 18 (ANI): A new research has concluded that increasing temperatures at high altitudes are fueling the post-1950 growth spurt seen in bristlecone pines, the world's oldest trees.
Pines close to treeline have wider annual growth rings for the period from 1951 to 2000 than for the previous 3,700 years, according to a University of Arizona (UA) led research team.
Regional temperatures have increased, particularly at high elevations, during the same 50-year time period.
"We're showing this increased growth rate at treeline in a number of locations," said Matthew W. Salzer, a research associate at UA's Laboratory of Tree-Ring Research. "It's unique in several millennia, and it's related specifically to treeline," he added.
Bristlecone pines live for thousands of years on dry, windswept, high-elevation mountain slopes in the western US.
The scientists collected and analyzed tree rings from Great Basin bristlecone pines located in three mountain ranges in eastern California and Nevada that are separated by hundreds of miles.
Only trees growing within about 500 feet (150 meters) of treeline showed the surge in growth. In general, those trees were at or above about 11,000 feet (3,300 meters) in elevation.You can come downslope less than 200 vertical meters and sample the same species of tree, and it won't show the same wide band of growth," Salzer said.
Growth at the pines' upper elevational range is limited by cold temperatures. At the lower elevations, growth of the trees is limited by moisture more than temperature, according to Salzer.
"Something very unusual is happening at high elevations, and this is one more piece of evidence for that," Co-author Malcolm K. Hughes said.
"There is increasingly rapid warming in western North America. The higher you go, the faster it's warming. We think our finding may be part of that whole phenomenon," he added.
Salzer and his team analyzed the average and median width of tree rings for 50-year blocks of time, starting with the latter half of the 20th century, the years 1951 to 2000, and going backward in time to 2650 B.C.
To see how the annual growth rings changed with temperature, the team used a new method of mapping climate data called PRISM (Parameter-elevation Regressions on Independent Slopes Model) that was unavailable to researchers 25 years ago.
PRISM combines weather records and knowledge of how topography affects weather and climate to provide state-of-the-art climate information going back 100 years for specific locations.
The tree-ring researchers found that the chronological timing of the wider tree rings correlates with increasing temperatures from the PRISM climate map. (ANI)