BUILDING A REGIONAL TREE-RING MASTER CHRONOLOGY FOR NORTHCENTRAL PENNSYLVANIA

Dendrochronology, or tree-ring dating, is a scientific method of matching the pattern of annual tree growth in a sequence of overlapping core samples from various wood sources, to pinpoint ages and analyze regional climate and environmental conditions. Beginning with live tree cores and finding progressively older samples, lengthy chronologies can be compiled. These chronologies allow cross-dating between specimens in a particular region and can extend backwards for thousands of years. This method, initially developed by astronomer A.E. Douglass in the 1920’s, is currently used by many archaeologists, climatologists, and environmental scientists in the temperate forest zones of the world, where trees are responsive to annual variations in climate.

This research addresses the lack of an existing chronology in north-central Pennsylvania, and aims to collect, analyze, and cross-date tree-ring samples within Tioga County to produce a master database for various research applications including climate change, ecological studies, geomorphic applications, and measuring pollution. Research agreements with the Department of Conservation and Natural Resources (DCNR) and State Game Commission (SGC) provide 184,207 acres for sampling. Eastern Hemlocks (Tsuga canadensis) were chosen as they are native to this region of Pennsylvania and they have the highest potential for matching rings, with a cross-dating index (CDI) rating of two. Likewise, the spread of the invasive hemlock wooly adelgid and the decline of the eastern hemlock throughout Appalachia provides further rationale. All samples are collected and analyzed according to standard dendrochronological field methods to ensure reliability of samples. Post-processing and analysis is performed with CDendro and CooRecorder software.