NOAA/WDS Paleoclimatology - González-Cásares - DUPC - PIEN - ITRDB MEXI114

Climate warming could intensify drought stress in NW Mexico mountains as the Sierra Madre Occidental which are not only centers of pine diversification but also subject to a high hydroclimatic variability. In this region, rainfall and thus forest growth depend on changes in sea-surface temperatures (SST) across the equatorial Pacific related to the El Nino Southern Oscillation (ENSO). Winter moist-cool conditions usually correspond to El Nino episodes characterized by warm SSTs in the equatorial Pacific, whilst dry winters correspond to cold SSTs (La Nina). Consequently, growth responsiveness to dry spells could be used as a proxy of forest vulnerability to increased drought stress. Here, we characterize the growth responsiveness of five coexisting Mexican pine species to hydroclimate, drought, and the ENSO using dendrochronology. Pinus lumholtzii and P. durangensis showed a low responsiveness to maximum temperatures and drought, whereas others as P. arizonica, P. engelmannii, and P. leiophylla were very responsive. Among these drought-sensitive pine species, we found responses to ca. half- (e.g. P. engelmannii) and 1-year long (e.g. P. arizonica) droughts. The most responsive species to drought, P. arizonica and P. leiophylla, were also those showing a higher association between ENSO-related indices and growth. Wet and cool winter and spring conditions, linked to warm SSTs over the equatorial Pacific, were the main hydroclimate factors enhancing growth. Pine species presented different growth responsiveness to drought which suggests that they present diverse tolerances to water shortage. This implies that coexisting pine species will differently face the more arid conditions forecasted for many drought-prone areas.