X-ray densitometry for identifying and measuring tree-rings in semi-arid species

Abstract

The presence of annual rings in tropical trees may allow the application of dendrochronological methods to determining age, growth rates and climate-growth relationships. In semi-arid tropical trees, annual rings are visible when the cambial dormancy is induced by annually climatic events, such as drought. However, seasonally and monthly variation in water availability may cause the formation of indistinct, narrow and irregular rings with ill- or non-defined annual rings, hindering tree dating and construction of tree-ring chronologies. X-ray densitometry is a method that can be very useful to identify the boundaries of the tree-rings and to build chronologies. In this study, we will apply the X-ray densitometry technique to build long tree-ring chronologies for species of the Brazilian flora. For this, we will use usual methods for sample preparation and analysis in wood anatomy analysis and X-ray densitometry. To build the chronology, density values will be tested between species using a linear mixed model (LMM) with type (maximum, mean and minimum values), species, and the interactions between them as fixed factors, and tree as random factor. This chronology will be used for climate reconstruction, contributing to the understanding of the climate of the Americas. (AU)