Climatic variability at the treeline of Monte Tlaloc, Mexico: a dendrochronological approach

Abstract

An increase in winter-spring precipitation appears to have a positive effect on radial growth of P. hartwegii a treeline species in Mexican volcanoes. To address the degree to which high-elevation trees reflect climatic variability, a ring-width chronology of 308 years (1705–2012) was developed from a pure stand of Pinus hartwegii forest at the upper treeline of Monte Tlaloc in the Trans-Mexican Volcanic System. A series of variables were used to verify the climatic correlation of the chronology, including climate data, historical archives dealing with agricultural crises and climate anomalies in central Mexico, regional dendroclimatic reconstructions of precipitation, values of the Southern Oscillation Index (SOI), and Tropical Rainfall Index, which are estimators of El Nino/Southern Oscillation phenomena (ENSO). Correlations with local and regional climate data suggested that wet conditions in the winter–spring season had a positive effect on radial growth. Reduced growth was associated with extreme droughts in central Mexico, with some exceptions, such as in 1997, when, due to the massive warming of sea surface temperatures and low precipitation, growth did not begin until May or June and peaked during the cool season. The ring-width chronology indicated an increase in radial growth when SOI values were negative and precipitation was above-mean during the growing season. The lowest recorded growth measurements are associated with extreme droughts and strong warm ENSO events. Given the significant relationship between climate and radial growth of P. hartwegii, this study highlights the potential vulnerability of this high-elevation species to climate change.