Rocky Mountain Tree-Ring Research

OldList is a database of ancient trees. Its purpose is to identify maximum ages that different species in different localities may attain such that exceptionally old age individuals are recognized. In addition to this original OldList, Neil Pederson at Harvard Forest and colleagues at the Virginia Tech Tree Program maintain a companion Eastern OldList, focused on old trees growing in the eastern United States.

May 2019: Amazingly enough, this month has brought in two new 2000+ year-old species from two areas of the world where old trees were previously known to occur, but not quite this old. Dave Stahle and colleagues found a new stand of very old bald cypress (Taxodium distichum) from the Black River in North Carolina, USA, with a new 5th oldest known individual coming in at 2,624 years old. Dave also maintains a terrific website on their bald cypress project that old tree enthusiasts should check out. And a new paper summarizing the oldest trees in China by Jiajia Liu and colleagues has just come out, with now the 7th oldest known species to be a Qilian juniper (Juniperus przewalskii) tree that was determined to be 2230 years old.

May 2017: A new old age tree record holder was recently recognized, a Pinus longaeva (Great Basin bristlecone pine) growing in the White Mountains of eastern California. The date on this tree was reported to me by the late Tom Harlan. The tree was cored by Edmund Schulman in the summer of 1957 but unfortunately Schulman never had a chance to date the tree before his untimely death in early 1958. Starting around 2009, Harlan worked up many of the cores Schulman collected that summer of 1957, and discovered the tree's age at that time. Tom reported to me in 2010 that the tree was still alive, and the age reported to me at that time was 5062 years old. HOWEVER, as of 2017, the age of this tree has not been able to be confirmed; the core dated by Tom Harlan has not been located at the Laboratory of Tree-Ring Research. Therefore, I have removed this tree from OldList until such time as it is able to be confirmed.

• 1996 paper on OldList
• Submit a tree for inclusion on OldList
• References for OldList trees

Five types of tree ages are recognized in the OldList database:

• XD: crossdated
• RC: ring counted
• EX: extrapolations (usually based on ring measurements)
• HI: historic record
• C14: radiocarbon dated wood samples from a tree (added 2007)

Crossdated ages are derived through recognized dendrochronological procedures (e.g., Stokes and Smiley 1968; Swetnam, Thompson, and Sutherland 1985; Schweingruber 1987; Speer 2010). For a crossdated age, there should be no question of the age of the portion of the tree sampled, except in any portion of the ring series not confidently crossdated with either other trees at the same site or other sites in the area. Ring-counted ages are derived by simple ring counts and may contain errors in age due to missing or false rings, suppressed areas, poorly surfaced samples, or other types of tree-ring anomalies (e.g., injuries). "Age" in these first two types will invariably be a minimum age rather than true chronological age owing to the difficulty of sampling a tree exactly at the point of germination. Extrapolations are ages derived by regression from age/size relationships (e.g. Stephenson and Demetry 1995) or other mathematical or graphical methods. Ranges of ages derived by extrapolations are welcome and can be accommodated in the database. Historical ages are based on some sort of historic reference to the tree. OldList contains only a single historical age, that for a Ficus religiosa at a Buddhist Temple in Anuradhapura, Sri Lanka. A continuous account of four trees planted in the 3rd century B.C. has been kept (letter to R.J. Hartesveldt from Ambassador of Sri Lanka in the USA, December 15, 1972). An individual tree may have up to two entries in the OldList database. For example, a tree may have one entry for the age of a crossdated radial increment core and a second for an extrapolation age to a possible pith or germination date.

A note here on radiocarbon ages of potentially very old trees. There has been a lot of focus on in the media recently about very old trees that are based on radiocarbon dating of a remnant piece of wood in association with a currently living tree that is assumed to have been an ancient stem that reproduced clonally. The most recent example is "Old Tjikko", a Norway spruce (Picea abies) growing in Sweden. The living stem itself is only a few hundred years old, but there is a radiocarbon age of 9,500 years from dead wood present at its base. The living tree is argued to be only the most recent ramet of the much older individual tree genet. However, a 2016 study by G. L. Mackenthun instead argues that there is no evidence of genetic continuity between the dead and living wood portions of the tree, nor is there any evidence of clonal origination of Norway spruce in general. Thus, in the absence of any evidence of genetic continuity between dead and living portions of a stem, especially from a species otherwise not known to commonly reproduce clonally, I do not include such trees in Oldlist.

However, radiocarbon ages of trees are considered if the date came from a piece of wood that can unequivocally be associated with the individual tree itself. For example, Patrut et al. (2007) used radiocarbon dating on pieces of what may be the largest known baobab (Adansonia digitata) to determine that the tree was at least 1250± 50 years old when it recently died. This is now the oldest confirmed age of an angiosperm tree, at least twice as old as the second oldest confirmed age for an angiosperm species (although note also the addition of two oaks reported in Jones 1959 that are 866 and 930 years, sent to me by Alexei Rivera; however, we cannot find the original references and these presumably ring-counted ages cannot be confirmed). I also must at some point soon go through the recent literature on radiocarbon ages found on several tree species in South American rain forests that are in some cases several hundred to over 1000 years old. But bottom line is that confirmed (i.e., crossdated) maximum ages of conifer species are typically an order of magnitude greater than crossdated angiosperm species.

(Larger version of header photo; bristlecone pine in the Patriarch Grove in the White Mountains, California)

Notes on dates:

* Tree is still living as of late 2010s; age given is additional years since it was first sampled when this is known.

** Tree is dead; age is at time of death.

Otherwise age shown is that at time of sampling.