摘要：Climate change is predicted to increase the frequency of severe drought, yet little information exists on the impacts of drought on dominant trees of Mexican pine forests, which are among the most biologically diverse forests in the world. We conducted the first comparison of growth sensitivity to drought of two co-occurringPinus species in Mexico to understand whether growth of dominant pines of the Sierra Madre Occidental in northern Mexico is sensitive to drought and temperature variation and to understand how sensitivity differs between tree species and elevations. We sampled and analyzed tree-ring data across a 400-m elevation gradient for the years 1945–2004 for co-occurring Pinus engelmannii and Pinus lumholtzii at Basaseachi National Park, Chihuahua, Mexico. We hypothesized that growth sensitivity to drought would be highest at low elevations, annual basal area increment (BAI) would be lowest at low elevations, and winter precipitation would covary positively with BAI at all elevations. Growth sensitivity to drought, as measured by a wet-dry ring-width index ratio (W:D), was significantly higher for both species at low elevations (W:D range 2.2–2.8) than at intermediate and high elevations (W:D range 1.5–1.9). Pinus engelmanniihad significantly higher W:D (2.2) than P. lumholtzii (1.8). Annual BAI did not differ between elevations or species. Annual ring–width index was positively and significantly associated with winter (December–April) precipitation. This association was stronger at low elevations than at high elevations. Other seasons of precipitation and other climatic variables were not significantly associated with annual growth. Our results suggest that the increasing frequency and severity of drought predicted for this region in the coming decades will reduce growth of P. engelmannii and P. lumholtzii, with greater impacts on low-elevation populations and on P. engelmannii.Se ha predicho que el cambio climático aumentará la frecuencia de las sequías severas, pero existe poca información sobre el impacto de la sequía en los árboles dominantes de los bosques de pino mexicanos, que son de los bosques con más diversidad biológica en todo el mundo. Llevamos a cabo la primera comparación de la sensibilidad a la sequía de dos especies simpátricas de Pinus en México para saber si el crecimiento de los pinos dominantes de la Sierra Madre Occidental en el norte de México es sensible a la sequía y a la variación en la temperatura y cómo la sensibilidad difiere entre especies y a diversas altitudes. Muestreamos y analizamos datos de anillos de Pinus engelmannii y Pinus lumholtzii simpátricos
