Abstract:
Old Douglas-fir (Pseudotsuga menziesii) trees were sampled in the Sierra Madre
Oriental of northeastern Mexico and used to develop a 219-year chronology of
earlywood width. This chronology is correlated with monthly precipitation
totals from January to June at Saltillo some 55 km northwest of the collection
site. The chronology was used to reconstruct winter-spring precipitation
(January-June
... total) from 1782-2000. The reconstruction indicates large
interannual, decadal, and multidecadal variability in winter-spring
precipitation over Saltillo. This variability is vaguely apparent in the
short and discontinuous instrumental record from 1950-1998, with January-June
totals ranging from 15 to 310 mm, multiyear droughts, and a negative trend in
January- June precipitation over the last 50 years. The reconstruction
indicates that severe dryness was prevalent over a 24-year period from
1857-1880. This mid-19th century drought exceeds the duration of any droughts
witnessed during the 20th century. However, three episodes of winter- spring
dryness have prevailed in the Saltillo region after 1950, a much higher
frequency of decadal drought than estimated over the past 219 years and
aggravating the regional water supply problems associated with this booming
manufacturing and ranching center. 
