Time and Location: Mondays at 1 pm, Comer Seminar Room
09/18/17: Brendan Buckley, LDEO
"Southeast Asian tree rings and hydroclimate: recent developments and future prospects"
Twenty years of tree-ring research in Southeast Asia has resulted in near-millennial length reconstructions of the regional hydroclimate using the rare cypress (Fokienia hodginsii) found growing along the length of the Annamite Range from 12° ‒ 23° N latitude. These records led to discoveries of severe climate anomalies that gripped the region and contributed to the demise of the Khmer at Angkor by the early 15th century, and the collapse of all major polities of the Indochina Peninsula by the late 18th century. Three published records of spring (March ‒ May) hydroclimate from north, central and southern Vietnam Fokienia represent the most robust and well-replicated tree ring records from anywhere in the global tropics, with two additional Fokienia records from north and central Vietnam currently in preparation for publication. Additional Fokienia collections from Lao PDR are being developed. We have also developed teak records from Myanmar, Thailand and Indonesia, and multiple records from Pinus species from Myanmar, Thailand, Cambodia and Laos.
This talk focuses on new developments in the methods we use to analyze tropical tree ring data. We are now able to account for discrete seasonal reconstructions of climate beyond the spring season, and include variability of the summer, autumn and winter seasons. In particular, Blue Light Intensity (BLI) is a proxy for wood density, and has been widely used in the high latitude forests where summer temperature dominates the growth response. We apply this technique to the earlywood of Fokienia hodginsii samples from Vietnam and find a response to winter (Dec-Apr) temperature strong enough to allow for robust statistical reconstruction. We interpret these results as reflecting a cavitation-avoidance response of this species, such that higher than average temperature during the annual winter dry period results in a reduction of lumen diameters during the springtime flush of growth (an interpretation supported by ongoing ecophysiological research). Stable isotope analyses of δ18O from Fokienia and Pinus species are revealing summer hydroclimate seasonality (May-Sep), while earlywood and latewood measurements from Pseudotsuga sinensis from northern Vietnam reflect autumn rainfall. The ability to analyze discreet seasonal climate variability from the tropics is new, and is a major development for studies of climate over Southeast Asia.
|Sep 18th||Brendan Buckley
|Southeast Asian tree rings and hydroclimate: recent developments and future prospects|
|Sep 25th||Tina Lüdecke
|Oct 2nd||David Talmy
|Oct 9th||Dana Royer
|Oct 16th||Valier Galy
|Oct 23rd||Kevin Becker
|Oct 30th||Rupsa Roy
|Nov 6th||no seminar|
|Nov 13th||Pamela McElwee
|Nov 20th||Charles Fisher
|Nov 27th||Yuri Gorokhovich
|Dec 4th||Michael Hren