tree rings

A new study soon to be published in Geophysical Research Letters finds a previously unknown multi-decade drought in the southwestern U.S. during the second century A.D.

Researchers at the University of Arizona were recently awarded $1.5 million over four years to study fire interactions in northern New Mexico’s Jemez Mountains. Using both tree-ring and archaeological methods, the scientists will shed light on how to live within these forests sustainably so they persist even in the face of climate change.

Sheppard, PR, Comrie AC, Packin GD, Angersbach K, Hughes MK.  2002.  The climate of the US Southwest. Climate Research. 21:219-238.

Time series plot of past Colorado River flows created by analyzing tree-rings. The plot displays the 25-year running average of the reconstructed flows. Flows are plotted as a percentage of the 1906–2004 average of observed natural flows (18.5 billion cubic meters or 15.0 million acre-feet). The red horizontal line is the lowest 25-year running mean of observed flows (1953-1977).

Posted by Michelli Murphy | on October 15, 2008
Researchers are using tree-rings to reconstruct past Colorado River streamflow to see how common, and extreme, southwestern drought can be—information that is vital to water managers.

How tree rings can lead to estimates of past streamflow is not readily obvious. It's natural to think that trees lined right along a river would act as the best gages. As it turns out, those trees are relatively useless - or complacent, as researchers call them. Even in times of drought, riverside trees draw up plenty of water from the moist soil, packing on wide growth rings year after year.