Tree-ring width indices (RWI) of an African baobab (Adansonia digitata) tree from Oman

The surface of the wood core was prepared with a razor blade perpendicular to the longitudinal stem growth and photographs were taken with a fluorescence microscope (Nikon MULTIZOOM AZ100M, V-2A: 380-420 nm; camera head: Nikon digital sight DS-Fi1c; light source: C-HGFI HG Precenteres Fiber Illumiator (130 W mercury lamp); program: NIS Elements 4.30.01© 1991-2014 Laboratory Imaging). Tree-ring width measurements were performed on a stitched panorama of overlapping core pictures by using Windendro (Regents Inst. Canada). Data was detrended using an exponential fit (R program, package dplR; Bunn et al., 2018) resulting in a dimensionless ring-width index chronology (RWI) for the time period 1911 to 2005CE.