Neotropical plant species produce charcoal particles distinguishable by morphometrics and morphotypes

Sedimentary charcoal analysis is a popular method to infer fuel sources and reconstruct paleofire and paleoecological history. However, existing proxy calibration experiments are concentrated on Palearctic and Nearctic floras, leaving tropical ecosystems understudied. To address this knowledge gap, we experimentally burned 21 Neotropical plant taxa and characterized charcoal morphology across tissues (leaf, wood, bark, stem) and growth habits (tree, shrub, liana, herb). We found that charcoal morphology is partitioned by tissue type: leaf tissues are significantly distinct from all others, yielding more circular and irregular particles, while wood and bark generate highly elongated particles. Notably, shrub wood produced charcoal with the highest mean length-to-width (L:W) ratios reported to date. Growth habits were also statistically distinguishable, with shrub and tree wood forming more elongated charcoal than lianas and herbs. We infer that these exceptionally high L:W values reflect ecophysiological adaptations to seasonal drought in Neotropical arboreal wood, which burns and fractures along elongated vessels and thick-walled fibers. Additionally, circularity emerged as a complementary morphometric for discriminating shape differences. Our results demonstrate a greater biogeographic heterogeneity of charcoal morphometrics than previously recognized, expanding the global reference dataset, and giving important methodological insights for future paleofire studies in the Neotropics. • First detailed charcoal morphometric dataset for tropical plant taxa. • Lignified wood and bark produce elongated particles with low circularity. • Mesophyll-rich leaves yield more circular and less elongated charcoal. • Established L:W and circularity thresholds for Neotropical fuel discrimination.