THE PRINCIPLE OF CROSS-DATINGMatching pa erns in tree-ring widths or other ring characteristics(such as ring density) among several trees allow the identiﬁcationof the exact year in which each ring was formed.
PLE -RING SAM EE HE TR N WH ERE T OSITI O LLEC TED!AT THE P WA S CO A “missing ring” is a term used to describe the phenomenon where a tree does not form wood around its trunk during a single growing season.
What kind of trees have rings that can be dated? • They have distinct and detectable rings. • Their rings must be reliably annual. • The formation of their rings must be sensitive to environmental conditions. • That sensitivity must cause the rings to vary from year to year. • Several trees must share common pa erns in tree-ring width, wood density or some other wood variable.
‘Complacent’ tree-ring series: • exhibit very li le year-to-year variation. • grow in se ings where the limiting growth factor doesn’t change much. • are tough to cross-date.‘Sensitive’ tree-ring series: • have wide and narrow rings that are intermixed through time. • Found in environments where the limiting factor is highly variable year to year • Matching ring pa erns across trees is easier.
September 20 The principle of cross-datingSource: Baillie (1982)