A Common Era Tree-Ring Chronology Sensitive to Cool-Season Temperatures for the Southern Hemisphere

Annually resolved multi-millennial records of temperature are rare in the Southern Hemisphere (SH), and even rarer are SH records of cool-season temperature. Here we present a new tree-ring chronology extending back to 42 BCE based on Athrotaxis selaginoides from southern Tasmania. The development of this chronology was complicated by multiple tree-age cohorts and growth classes. Additionally, there was a collapse in sample depth between the mid-14th and mid-16th Centuries. Therefore, we used a multiple Regional Curve Standardization (mRCS) approach to standardization but have subsequently employed piecewise adaptive detrending (PAD). PAD utilizes the Friedman Supersmoother to remove the remaining multimillennial trend likely to be the result of changing site conditions rather than climate. The chronology is significantly associated with temperature from winter through to the end of the warm season, but its association with Austral July-October temperatures is both unusual and stable. The collapse in sample depth, and four clear cohorts of trees are most likely associated with landscape scale fire events.