The influence of climate on the masting behavior of Mexican beech: growth rings and xylem anatomy

Abstract

The Mexican beech undergoes masting events, on average, every 5.5 years. These events depend directly on precipitation. Climate change has considerably impacted the protective functions of tropical montane cloud forests, possibly influencing the synchronicity of phenological processes and the distribution and physiology of plants. In particular, climatic fluctuations cause changes in the distribution of tree species. Mexican beech (Fagus grandifolia subsp. mexicana) is considered an endangered species, due to its restricted distribution and its being a Miocene relict, limited to tropical montane cloud forests in the mountains of the Sierra Madre Oriental in eastern Mexico. We analyzed the influence of temperature and precipitation in prompting changes to tree-ring width, as well as vessel frequency and diameter, of Mexican beech in eastern Mexico. We used growth rings and xylem vessels traits to infer the historical masting events of Mexican beech over the last 128 years. We obtained independent chronologies for Mexican beech in each of the studied sites, dating back 152–178 years. Precipitation was strongly associated with differences in tree-ring width between masting and non-masting years. Our study highlights the use of dendroecological research to detect climate-induced modifications in the vessel frequency and diameter of tree species inhabiting tropical montane cloud forests. This association also explained differences in vessel frequency and diameter recorded before, during, and after masting events. Our results revealed that Mexican beech undergoes masting events every 5.5 years on average, and that these events directly depend on minimum annual precipitation. In conclusion, our results advance our understanding on the plasticity of growth rings and vessels traits (frequency and diameter) in response to fluctuation in precipitation.