|
||
|
OLDLIST:
A Database of Maximum Tree Ages;
Peter
M. Brown
Text of a paper published in: J.S. Dean, D.M. Meko, and T.W. Swetnam (eds) 1996. Proceedings of the International Conference on Tree Rings, Environment, and Humanity: Relationships and Processes, 17-21 May, 1994, Tucson, Arizona. Radiocarbon 1996:727-731. |
||
| Abstract OLDLIST is a database containing maximum ages of trees by species. The purpose of the database is to serve as a baseline for the maximum known ages of different species, such that individual trees of exceptional ages may be recognized. A portion of the database listing the oldest trees of 30 different species is given. The oldest species in the database is Pinus longaeva, with the oldest individual tree at 4,844 years old. The oldest angiosperm tree in the database is a Quercus alba at 407 years old. A request is made to interested scientists to contribute to the database. | ||
| Introduction
There
is ever increasing awareness among the general public and managers of both
public and private lands of the ecological, scientific, and esthetic values
of old-growth forest ecosystems (Whitney 1987; Juday 1988; Kaufmann, Moir,
and Bassett 1992). Dendrochronologists especially can appreciate
the invaluable scientific resources contained in old-age forests (Shepperd
and Cook 1988; Van Pelt and Swetnam 1990). The discovery and analysis of
long tree-ring records often provides new insights into dynamical systems
such as climate or forest disturbance processes. Paleoclimatic and
paleoecological data are crucial to provide longer-term records of environmental
variability against which to assess potential human-induced environmental
changes. Often older-aged stands or trees are located in marginal
sites that are more sensitive to climate variations and are protected from
harvesting or other human disturbance. Furthermore, old-age stands
are often remnant examples of relatively pristine forest conditions contained
within a more widespread matrix of second-growth forest. These stands
act as natural laboratories for understanding ecological processes in the
absence of human disturbances (Stahle and Chaney 1994).
However, an essential question can arise when defining "old-growth" for a given forest type or species: exactly how old is "old"? This question increases in importance when attempting to recognize exceptionally ancient stands or individual trees that arguably should have special protection from harvesting or other human activities (Van Pelt and Swetnam 1990; Swetnam and Brown 1992; Stahle and Chaney 1994). An example is the designation of Research Natural Areas on US Forest Service lands, where old age is a primary criterium for inclusion. While many of the oldest stands or trees may not have commercial value, they may be under treat of destruction from other development activities. One example is a stand in New Mexico, USA, that contains the oldest-known limber pine (Pinus flexilis) and is only a few kilometers from a large and growing molybdenum mine (Swetnam and Brown 1992). I have compiled a database - OLDLIST - of the maximum known ages that trees from different species may attain. The database contains ages from individual trees of over 30 species. Several of these species are represented by more than one tree from different geographic locations. The principle idea behind the OLDLIST database is to serve as a baseline of the maximum known ages of a species, such that exceptionally old-age trees or stands of a species may be recognized. Researchers with exceptionally ancient trees may then have some greater justification to argue for special protection or status for their study area. |
||
| The
OLDLIST database
OLDLIST
is a Paradox database consisting of 14 fields. I recognize 4 types of age determinations in
the database. Crossdated ages are derived through recognized
dendrochronological procedures (e.g., Stokes and Smiley 1968; Swetnam,
Thompson, and Sutherland 1985; Schweingruber 1987). 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. Crossdated ages also include the beginning and ending calendrical dates for the sampled portion of the tree.
Ring-counted ages are derived by simple ring counts and may contain errors
in age due to missing or false rings, suppressed areas, or other tree ring
anomalies. "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 upon historical reference
to the tree. At present, OLDLIST contains only one historical age,
that for Ficus religiosa at a Buddhist Temple in Anuradhapura, Sri
Lanka. A continuous historical account of four trees planted there
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 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.
The database at present contains ages on over 60 trees representing over 30 species. The oldest trees are of the species Pinus longaeva, the bristlecone pine of the White Mountains and Great Basin in western USA. The oldest tree known is the infamous "Currey Tree" of eastern Nevada at close to 4900 years old (Currey 1965). The bristlecone pine is the only species known to live over 4000 years. The second oldest tree is from the South American species, Fitzroya cupressoides. The great age potential of this species was recently discovered (Lara and Villalba 1993) and supplanted the long-known old-age species from California's Sierra Nevada Mountains, Sequoiadendron giganteum or giant sequoia, as the second oldest. At least 13 other species are known or suspected to live over 1000 years old. The oldest known crossdated angiosperm species are those of Quercus, but these only live to be just over 400 years old at most, an order of magnitude less in age than the oldest gymnosperms. |
||
| Conclusion The interests and objectives of dendrochronologists often lead us to look for sites that contain old-age trees to obtain a maximum length of time series for climate reconstruction or other tree-ring studies. OLDLIST is in its infancy. I have not made a great effort to contact researchers with old trees and have very few entries in the database outside of western North American species. I am therefore calling upon all interested dendrochronologists and others working with tree ages to send me their oldest trees of whatever species from whatever locale. If you have what you believe is an ancient tree or know of a reference to one and would like to contribute to this database, please use table 1 as a template for your entry and send it to me at the address above (preferably email). I envision the OLDLIST database to be a well-documented repository of ages of old trees where a researcher may go to check if she or he has a tree or stand of extraordinary antiquity. If so, one may then have a better argument to make to funding or management agencies for perhaps some special protection of that study site. In addition, we now have a place to turn when inevitably asked by the interested public or other scientists questions such as, "what is the oldest tree?", or, "how old can this species get?". | ||
| Acknowledgements I thank all of the dendrochronologists and other researchers who have so far sent me information on their old trees. Thomas W. Swetnam and David W. Stahle provided invaluable comments about the manuscript. | ||
References
|
||
|
Page last
updated: January 2008 |
