THE OLDEST KNOWN ROCKY-MOUNTAIN BRISTLECONE-PINES (PINUS-ARISTATA ENGELM)

We have found 12 living Rocky Mountain bristlecone pines (Pinus aristata) more than 1600 yr old, including four that are more than 2100 yr old, on Black Mountain, near South Park, and on Almagre Mountain, in the southern Front Range, Colorado. A core from the oldest of these trees has an inner-ring date of 442 B.C. This tree is therefore at least 2435 yr old and exceeds the age of the oldest previously reported Rocky Mountain bristlecone pine by 846 yr. The ages of these trees show that Rocky Mountain bristlecone pines, under arid environmental conditions, achieve much older ages than have been previously reported. The ages also show that previously inferred trends in bristlecone pine ages, where maximum ages in the eastern range of Rocky Mountain bristlecone pines are much less than maximum ages in the western range of Great Basin bristlecone pines (Pinus longaeva), are less strong than previously supposed. Ancient Rocky Mountain bristlecone pines, such as those found in this study, have the potential to expand our knowledge of late Holocene climatic conditions in western North America.