Paleo Slide Set: Tree Rings: Ancient Chronicles of Environmental Change
Locally absent ring in Scots pine (Pinus sylvestris).

Under other climate conditions, trees may produce only a partial ring 
or may fail to produce a ring at all. This may occur in a year in which 
conditions for growth are particularly harsh. These rings are called 
locally absent or missing rings and are commonly found in trees which 
are extremely sensitive to climate. A partial ring is visible in the 
upper portion of this slide. This ring gets pinched between the rings 
to the left and right of it and is not visible at all in the lower 
portion of the slide. Very old and/or stressed trees may also produce 
very small, barely visible rings only a few cells wide which are called 
micro-rings. Because of the occurrence of false, locally absent, micro, 
and missing rings, it is especially important to prepare surfaces carefully 
and use the technique of crossdating to ensure exact calendar year dates 
for individual rings. More about this later!

Photo Credits:
Jonathan Pilcher
Palaeoecology Centre, Queen's University, Belfast