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Los anillos de crecimiento de Pinus cembroides se emplearon como proxy para reconstruir la variabilidad histórica de la precipitación anual durante 159 años (1850 a 2008) en la región oriental del estado de Tlaxcala. La reconstrucción mostró alta variación interanual y entre décadas en las lluvias. Las sequías más intensas se registraron para los periodos de 1887 a 1904, de 1969 a 1975 y de 1982 a 1991; de igual manera, se detectaron lapsos con precipitaciones superiores a la media regional de 1860 a 1863, de 1867 a 1876, de 1905 a 1909, de 1934 a 1940, de 1967 a 1969, de 1981 a 1982, de 1992 a 1993 y de 2000 a 2001. De mediados del siglo XX a principios del XXI se observó una influencia positiva de la Oscilación del Sur El Niño (ENSO, por sus siglas en inglés) sobre la alteración de la precipitación en años específicos, así como en la aparición tardía del Monzón de Norteamérica (NAMS, por sus siglas en inglés), particularmente, de 1970 a 1974, de 1988 a 1989 y de 1998 a 1999, lo que provocó fuertes periodos secos, que tuvieron un impacto social y económico importante; un ejemplo claro es el que aconteció en los años 70, cuando la interacción de ambos fenómenos dio origen al agostamiento más intenso en el periodo analizado para esta zona del estado.

The purpose of this study was to reconstruct the precipitation at Basaseachi National Park (BNP) in Chihuahua, Mexico. Tree-ring samples from pine species including Pinus durangensis, P. lumholtzii and P.engelmannii were collected in and near BNP and they were cross-dated with existing chronologies. Ring widths of each sample were measured and models to remove non-climatic trends from the data were applied. The relationship between precipitation from the weather station in Yécora, Sonora, and the ring width indices were modeled using a bivariate linear regression (r² = 0,59, p<0.01). It was found that precipitation from the months of October, December, February and April was most highly correlated with tree ring growth. The reconstruction extends 225 years from 2007-1782. During this time period there were thirteen severe droughts, ten of which affected large areas in northern and central Mexico. [ABSTRACT FROM AUTHOR]

Earlywood, latewood, and total ring width series from Pseudotsuga menziesii were developed in a mixed conifer forest at "Cerro El Mohinora", Chihuahua. The tree-ring series extended for the period 1657-2005 (349 years) and were used to analyze hydroclimatic variability for southwestern Chihuahua. A seasonal winter-spring precipitation reconstruction was developed with the objective of determining high and low frequency precipitation variability and analyzing the impact of dominant atmospheric circulatory patterns. The reconstruction indicated high interannual, decadal and multiannual variability. Severe droughts were reconstructed for the periods 1695-1715, 1753-1760, 1785-1792, 1798-1806, 1819-1830, 1841-1870, 1890-1897, 1906-1912, 1924-1941, 1971-1977, and 1994-2005. The most extended droughts took place in the periods 1695-1715, 1841-1870, and 1924-1941. The last three decades of the 20th century and the current years of the 21st century have been particularly dry for northwestern Chihuahua but the ecological and socieoconomical impacts have not been determined. [ABSTRACT FROM AUTHOR]

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