Using wood autofluorescence to explore the diversity of wood anatomy in the tropics and improve tree-ring visualization
Exploring new study sites and potential species is still a fundamental step in tropical dendrochronology. The results of exploratory field campaigns usually reflect the intrinsic biodiversity of the tropics: a plethora of wood anatomy variation and seemly true tree-ring boundaries. Often, some species are excluded during the process of selecting the best species due to indistinct or rather unclear tree-ring delimitation, aside from the difficult task to discriminate the commonly found false rings. Thus, any method that can improve tree-ring visualization is of great value to the development of tropical dendrochronology. We tested the use of wood autofluorescence to aid the process of species selection and tree-ring visualization. Using different combinations of filtered wavelengths in a fluorescence stereomicroscope, we evaluated the potential improvements in the visualization of wood anatomy and tree-ring boundary. We tested this method with 38 species and more than half showed some improvement in tree-ring visualization without any additional surface preparation. Our results also show the enhanced contrast among fibres, vessels, and parenchyma that can aid automatic detection and improve measurements in anatomical studies. We observed distinct growth rings in tree species previously described as bearing indistinct tree-ring boundaries and were able to highlight differences between true and false rings in Cedrela fissilis and Hymenaea courbaril. Although the wood autofluorescence should not be seen as a silver bullet for the rather challenging tropical tree species, it is certainly an additional method available in many research institutions that could significantly leverage dendrochronology in the tropics.