The Adaptive Morphology of Ancient Siberian Pine and Impacts on Tree-ring Proxies

Authors: Caroline Leland*, Columbia University, Edward R. Cook, Lamont-Dohery Earth Observatory, Laia Andreu-Hayles, Lamont-Doherty Earth Observatory, Amy Hessl, West Virginia University, Neil Pederson, Harvard Forest, Kevin Anchukaitis, University of Arizona, Baatarbileg Nachin, National University of Mongolia, Oyunsanaa Byambasuren, National University of Mongolia
Topics: Paleoenvironmental Change
Keywords: dendrochronology, tree physiology, stable isotopes
Session Type: Paper
Day: 4/6/2019
Start / End Time: 1:10 PM / 2:50 PM
Room: Marshall East, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Ancient Siberian pine trees growing on lava fields of central Mongolia have a weathered and stressed appearance, which is a testament to the harsh landscape they inhabit and the extreme climate they have endured for centuries. Many of the oldest individuals have “strip bark”, a morphological characteristic in which a discrete axis of the stem dies while the remainder of the tree continues to grow. Little is understood about the impacts of partial stem dieback on the physiology of trees, and whether such changes can influence radial growth trends on the living portion of the stem. We investigate ring width and stable isotopes from Siberian pine trees with strip-bark morphology for comparison against trees with a full cambium (“whole-bark” trees). We find that ring widths of strip-bark trees abruptly increase relative to whole-bark trees starting around the turn of the 20th century. This large radial growth increase most frequently follows a period of widespread stem dieback during the cold and relatively dry mid-19th century in central Mongolia, suggesting that stem cambial dieback might directly yield increasing ring widths on the remaining stem axis. Coincident with this increasing growth trend, tree-ring stable isotopes suggest that stomatal conductance declines after partial stem dieback occurs in Siberian pine, which could reflect an increase in the ratio of leaf-to-sapwood area. Given that partial cambial dieback appears to leave a signature on both tree-ring width and stable isotope proxies, careful data treatment should be employed when using strip-bark trees for reconstructions of past climate.

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