Sonora Pass Junipers, California

Research has been carried out over the past four years on high-altitude juniper trees, duniperus Occidentalis, from the Sonora Pass of the Sierria-Nevada mountains in California. The chronology is 3,507 years long and is composed of over 60 individual radii from six juniper trees. Research started in 1992 when a downed log section of juniper was found on a ledge above the canyon, about 9,000 to 10,000 feet up. It was measured and was found to have 1810 rings and named the 'Miles Juniper'.

In 1994 a second dead tree was discovered and christened the 'Scofield Juniper'. This was retrieved the following summer in 1995 with help from the National Forest Service in the Stanislaus National Forest. In 1996 the sample was sectioned and mounted, and was found to have 2,675 years growth in it.

Construction of a 3500 year Chronology

Initial analysis of the two trees showed that they matched well together, with one having died some 700 years earlier then the other. By combining both of these, a floating chronology totalling 3,385 years was compiled. In 1997 increment cores were taken from four living trees, thus dating the 'Miles' Juniper from AD 65 to AD 1875. Consequently the Scofield Juniper was found to have a first measured ring of 1510 BC, and last ring date of AD 1165.

Thus two trees have been identified and dated, one of 1810 rings and the other of 2675 rings. These together with four other living trees have been cross-dated and a 3,507 year long chronology, SONORA98, constructed.

Dr Henri Grissino-Mayer puts this in perspective by stating that hitherto, only 13 juniper chronologies have been published, the longest of them from Oregon spanning the years AD 1097-1982. Other chronologies are being worked on by Dr Lisa Graumlich of the Laboratory of Tree-Ring Research in Arizona but only date back to about 1000 BC, making SONORA98 the longest chronology yet developed.

Finally-the 'Scofield' Juniper with 2,675 rings is the oldest juniper found which has been accurately dated and the eight oldest tree record in the world. The next oldest juniper found is specimen CRE 175 from E1 Malpais National Monument in northern New Mexico, with 1,889 cross-dated growth rings.