Dendrochronological (tree-ring) studies allow scientists to identify and date droughts and other climate-driven environmental changes. Thin annual rings reflect years of lower precipitation and slower tree growth; thicker annual rings reflect years of higher precipitation and faster tree growth.
|A dendrochronologist cores an in-place roof beam in an ancient pueblo. The growth rings revealed in the sample are a record of the environmental conditions over the life of the tree. The same wood core could also be used to date the construction of this structure; see discussion under dating.|
Tree-ring studies allow us to study environmental change not only in the past but today as well. For example, bristlecone pines are particularly responsive to fluctuations in temperature, growing faster at higher temperatures. As the climate has warmed in the last half-century or so, tree line (the upper limit of where trees grow on mountainsides) has advanced upslope and the width of the Bristlecones’ annual rings has increased. (Source: Scientific American, 2009).
|Bristlecone pine (mikenorton/Bigstock.com).|
The Laboratory of Tree-Ring Research in Tucson is the world's oldest dendrochronology lab; their website includes information for researchers and the general public.
The Science of Tree Rings is an educational website with lots of information—from basic definitions and principles to links to tree-ring databases and other resources.