The oldest dated tree of Europe lives in the wild Pollino massif: Italus , a strip‐bark Heldreich's pine

How long do the oldest trees in Europe live? And where do they live? Recently, Konter et al. (2017) documented the discovery in Greece of Adonis, a Pinus heldreichii H.Christ with at least 1,075 tree rings, thus the oldest tree so far scientifically dated in Europe. An area of extreme interest to further explore these questions is the Pollino National Park (southern Italy, see Appendix S2), where maximum crossdated age of Heldreich’s pine had been previously reported as approaching a thousand years (Serre-Bachet 1985, Biondi 1992). After a 3-yr sampling campaign, we discovered a few millennium-old trees living on high-mountain cliffs (1,850– 2,150 m a.s.l.) in the Pollino Massif. The oldest sampled tree, which we called Italus (Fig. 1), became the subject of further investigation to determine its actual age. Italus has the typical shape of extremely old conifers, with dead spike top, strip-bark formation, and few live crown patches in the lower-middle part of the stem (Swetnam and Brown 1992). This Heldreich’s pine has diameter at breast height of 160 cm and is located on a steep rocky slope with cliff ledges. The stand is open, with little or no understory, generally undeveloped soils, and plenty of exposed dolomitic bedrock, hence the risk of wildfire spread is minimized. The Heldreich’s pine population occupies the vegetation zone just above beech forests that include old-growth stands with 500-yr old individuals, approaching the maximum longevity for this deciduous species (Di Filippo et al. 2015). Wood cores 5-mm in diameter were extracted using increment borers from the lower stem, which was hollow, and from exposed roots. Thanks to the particular configuration of the stem, straddling rocky and steep terrain that had eroded away, it was possible to collect increment cores from the root system close to the germination pith. To obtain a scientifically validated age for this old hollow tree, we developed a specific multistep dating procedure that combines tree-ring and radiocarbon analyses to match samples from a hollow stem and from exposed roots of a living tree. Increment cores extracted from the Italus stem revealed an innermost ring date of 955 CE, giving a total chronology length of 1,062 yr (955 CE–2,016 CE) (Fig. 2). Overall, ring-width patterns of Italus follow the typical features of isolated old trees, with relatively large increments in the first few cambial years, followed by a rapid decline towards a very long series of extremely small rings (Biondi and Qeadan 2008). Xylem increment is extremely low because of difficult environmental conditions, which typically lead to presence of extremely old individuals, as is the case with Pinus longaeva in Great Basin mountains of north America (Schulman 1954). A potential age estimate was then calculated using the increment core length and the stem diameter at the coring location. Given a 23.8 cm distance between the end of the core and the stem center (assuming a circular trunk), we used the average ring width for the innermost 20-50 rings (Di Filippo et al. 2017) to derive an estimate of 205–227 rings between the pith and the first dated ring. With this estimate, the pith date could fall in the 727–749 CE time interval. The total estimated stem age, obtained by adding the number of crossdated tree rings with the estimated missing ones, could therefore be 1,267–1,289 yr. Improving the age determination for Italus required analyzing the increment cores collected from the exposed roots. Anatomical features of root samples, such as the clear presence of latewood, indicated that those roots had been exposed for quite some time. Exposed roots often contain ring patterns that are not synchronous with rings in buried roots, and in our case there was also no clear correlation with the stem ring-width patterns. An abrupt growth decline was evident in the stem ring widths (Fig. 2) between 1,016