Tree Rings and Climate: Sharpening the Focus - Dendroclimatology - page 342

timescales has used tree-ring networks (for example, Stockton and Meko 1975 ,
1983 ; Stahle and Cleaveland 1992 ; Hughes and Brown 1992 ; Graumlich 1993 ;
Villalba et al. 1998 ; Hughes and Funkhouser 1998 ; Cook et al. 1999 , 2004b ; Stahle
et al. 2000 , 2007 ; Meko and Woodhouse 2005 ; Nietal. 2002 ; Touchan et al. 2005 ,
2008 ; Woodhouse et al. 2006 ; Davietal. 2006 ; Mekoetal. 2007 ; Christie et al.
2009 ; Le Quesne et al. 2009 ) . For obvious reasons, drought has been a major
focus of most of these studies; however, more recently, streamflow reconstruc-
tion has received greater attention (Stockton and Jacoby 1976 ; Cook and Jacoby
1983 ; Cleaveland and Stahle 1989 ; Andreev et al. 1999 ; Case and Macdonald
2003 ; Mekoetal. 2001 , 2007 ; Meko and Woodhouse 2005 ; Graham and Hughes
2007 ; Gou et al. 2007 ; Laraetal. 2008 ) , as warming trends in various parts of
the world, coupled with persistent drought conditions, have sparked the interest of
water resources managers and policy makers (Meko and Woodhouse, Chapter 8 ,this
volume).
Severe and persistent drought has been commonplace in the western United
States throughout much of the first decade of the twenty-first century, and this has
led to concerns about declining snow packs (Mote et al. 2005 ) , diminished stream-
flow (Stewart et al. 2005 ) , and lowering reservoirs (Pulwarty et al. 2005 ) . In the
face of climate change analyses (Barnett et al. 2008 ) , these concerns have spurred
water resources managers to evaluate longer hydrological baselines that are possi-
ble through tree-ring reconstructions. Studies such as those of Woodhouse ( 2003 ) ;
Woodhouse et al. ( 2006 ) , and Meko et al. ( 2007 ) have helped reservoir managers
across the western United States gain a better understanding of the historical range
of climate variability in the region—which has exhibited larger fluctuations than
anything experienced in historical times (Stine 1994 ; Cook et al. 2004b ; Graham
and Hughes 2007 ; Graham et al. 2007 ) .
In parallel to these tree-ring-based studies focused on developing longer base-
lines for assessing current and future hydroclimatic changes in the western United
States, some innovative studies using tree rings and other paleoenvironmental proxy
records suggest that abandonment of the Four Corners Pueblo cultures in the south-
west United States may have resulted from reductions in both cool and warm season
precipitation, leading to low maize yields and the collapse of settlements (Benson
et al. 2007 ) .Likewise,Stahleetal.( 2007 ) show that megadroughts occurred several
times in the prehistoric tree-ring-based record in the western United States, with
enormous consequences for the indigenous peoples in the region. In the sixteenth
century, drought affected large portions of North America (including Mexico). Other
notable works are those of Stahle et al. ( 2000 ) , Acuña Soto et al. ( 2002 ) , and Therrell
et al. ( 2004 ) , who establish a plausible link between severe pre- and post-Columbian
droughts in Mexico and pandemic outbreaks of diseases that likely led to the deaths
of millions of people. Of historical interest in the United States is the study by Stahle
et al. ( 1998 ) , which documents the occurrence (using tree-ring reconstructions) of
a historically extreme drought in the middle Atlantic region coincident with the
attempted establishment of English settlements in the New World. Stahle and Dean
( Chapter 10 , this volume) further discuss the nexus between climate extremes and
social disasters.