Age structure and climate sensitivity of a high Andean relict forest of Polylepis rodolfo-vasquezii in central Peru

The state of fragmented populations of tree Polylepis genus heavily impact by human activities leads to the need to conduct ecological studies to better understand their vulnerability. We evaluated the newly identified tree species Polylepis rodolfo-vasquezii, endemic to central Peruvian Andes, distributed from 3700 to 4750 m a.s.l. and suitable for dendrochronological studies. Our objectives were twofold: (1) to determinate age population in both forests and developed linear models that compared the relationships between tree size and age; (2) to assess the synchronicity in tree growth and climate sensitivity of the tree-ring chronologies. We present a newly developed 191-year tree-ring chronology, located at 11°S and 75°W, together with an update of the 157-year tree-ring chronology previously published from a forest nearby at 36 km of distance. The radiocarbon bomb pulse dating determined that the seasonal pattern of radial growth for these trees is primarily annual. Distinct tree age-size correlations were found in both populations, possibly explained by natural disturbances and human activities. Nevertheless, significant low correlation was found between growth patterns from both chronologies, and they shared high sensitivity to temperature of the current growing season. Our findings report that P. rodolfo-vasquezii is the second oldest Polylepis tree species reaching ages of 190 years old. Also, an important take-home message is that in this tree species allometric variables cannot be used to estimate tree age. P. rodolfo-vasquezii represents a unique tree-ring archives to understand past environmental history in the high central Andean in South America.