Same environmental forcings Similar growth pa erns
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.
Widespread drought caused narrow rings to form across the southwest USA during 1748 and 1750.Source: Kurt Kipfmueller
What kind of trees have rings that can bedated? • 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.