Maximum tree lifespans derived from public-domain dendrochronological data

The public-domain International Tree-Ring Data Bank (ITRDB) is an under-utilized dataset to improve existing estimates of global tree longevity. Since dendrochronologists have usually targeted the oldest trees in a stand, this public-domain resource is bound to offer better estimates of maximum tree age than those available from randomized plots or grid-based forest inventories. We used the longest continuous ring-width series of existing ITRDB collections as an index of maximum tree age for that species and site. Using a total of 3679 collections, we obtained longevity estimates for 236 unique tree species, 156 conifers and 80 angiosperms, distributed all over the world. More than half of the species (167) were represented by no more than 10 collections, and a similar number of species (144) reached longevity greater than 300 years. Maximum tree ages exceeded 1000 years for several species (22), all of them conifers, while angiosperm longevity peaked around 500 years. As new collections are constantly being added to the ITRDB, estimates of tree longevity may change slightly, mainly by adding new species to the database. Given the current emphasis on identifying human-induced impacts on global systems, detailed analyses of ITRDB holdings provide one of the most reliable sources of information for tree longevity as an ecological trait. Key Message Baseline information on tree longevity was derived from the most extensive dendrochronological database currently available. The resulting summary provides a reference point, to be used for modeling and research purposes.