Reconstrucción de la precipitación estacional para el barlovento de la Sierra Madre Occidental con anillos de crecimiento de Pseudotsuga menziesii (Mirb.) Franco

northwest mexico is a leader region in terms of agriculture, but is highly dependant on aquifers and on surface water from watersheds of the sierra madre occidental draining toward the pacific. paleoclimate studies to determine historical hydroclimate variability are rare in this region. two earlywood chronologies of pseudotsuga menziesii were developed for mixed-conifer stands in the sierra madre occidental. one of them is 531 years in length (1472-2002) and is located in tutuaca, chihuahua; the second one located in el cócono, guanaceví, durango, is 554 years length (1449-2002). the earlywood chronologies are significantly related to the seasonal winter-spring precipitation (october-may) and respond similarly (r = 0.61, p<0.00001; period 1472-1999) to precipitation. they detect drought periods of greater intensity than those witnessed during the 20th century. the most intensive and prolonged drought episodes were reconstructed for the 1560s, 1700s, and 1770s. historical archives indicate that some of these droughts were related to famine and epidemic outbreaks. the warm phase of enso has a strong signal in this region and produces above normal precipitation, whereas the cold phase is related to drought. moreover, the enso signal is not stable and changes through time as indicated by the correlation between precipitation and the tropical rainfall index. the development of a greater number of tree-ring chronologies is basic to understand the hydroclimate variability of the warm season (summer), which is of greater hydrological importance.