Elucidating tree-ring annual periodicity in tropical Bolivian Andes Prosopis alba through radiocarbon and wood anatomy analysis.

Keywords: Dendrochronology, Prosopis alba, South America, Bolivia, Radiocarbon, Wood anatomy.
Session Type: Virtual Paper Abstract
Day: Monday
Session Start / End Time: 2/28/2022 11:20 AM (Eastern Time (US & Canada)) - 2/28/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 40

Abstract

Tree-ring boundaries in tropical species are often less clear and less reliable than its counterparts from temperate zones. While in extratropical areas well-defined changes in temperatures drive the onset and offset of the growing season, in tropical environments trees may experience cambial dormancy related with the hydrological cycle such as dry seasons or heavy rain periods. In addition, intra-seasonal fluctuations on climate may cause the formation of false rings, wedging rings or unclear anatomical ring features. Here, we present an annual tree-ring chronology of Prosopis alba, a species growing on southern Bolivia highlands where a distinctive rain season occurs during austral summer. While annual periodicity has been reported for other Prosopis species like P. ferox and P. flexuosa, the dendrochronological potential of P. alba remains unknown. We collected several discs of P. alba, which where visually crossdated, and measured a minimum of 4 radii per tree. We found correlation coefficients values among different trees radii ranging from 0.3 to 0.5, showing some degree of growth synchronicity among trees. To validate the dendrochronologically-dated calendar years, we performed radiocarbon analysis obtaining offsets of 5 and 12 years on two analysed samples. We perform stem microsections to have a finer detail of the specific anatomical characteristics. Wood microsections revealed very narrow terminal parenchyma defining tree-ring boundaries, undetectable using classical approaches. Our work points out radiocarbon and wood anatomical analyses as key tools to generate tree-ring chronologies with annual resolution in some tropical tree species, and the potential of P. alba for dendrochronological studies.