Fire is inextricably linked to the vegetation that provides the fuel load. For palaeofire records to contribute meaningfully to the reconstruction of past landscape fire history, it is helpful to identify the vegetation that has been burnt, for example, grassy versus woody vegetation in tropical savannas. The morphological characteristics of charcoal particles can provide useful information on source vegetation type, and the aspect ratio of charcoal particles has been proposed to identify the contribution of grasses to environmental records. Stable carbon isotope analysis of pyrogenic carbon can also chemically identify the proportion of C₃ and C₄ biomass in charcoal samples but has yet to be widely applied alongside charcoal morphological analysis. Using carbon isotope analysis we demonstrate that C₃ sedges contribute elongate charcoal to a fire record where C₄ grasses are absent. These results challenge the widespread assumption that elongate charcoal is primarily or exclusively derived from grass, as most experimental studies demonstrating this relationship were conducted in environments where graminoids (grass-like forms) did not significantly contribute to available fuels. In turn, this complicates the simple interpretation of elongate aspect ratios for charcoal in fire records as direct proxies for the proportion of grasses in an environment, beyond differentiating temperate forests from grasslands. Minimal work to date has been done on separating charcoal derived from different graminoid types and future studies would benefit from the ability to differentiate graminoids including Poaceae and Cyperaceae in fire records. These results highlight the benefits of a multi-proxy approach to the interpretation of fire records in tropical savannas.

火与提供燃料负荷的植被密不可分。为了使古火记录对过去的景观火史的重建产生有意义的贡献，有助于识别已燃烧的植被，例如热带稀树草原的草木植被与木本植被。木炭颗粒的形态特征可以提供有关源植被类型的有用信息，并且提出了木炭颗粒的纵横比以识别草对环境记录的贡献。热解碳的稳定碳同位素分析还可以化学鉴定C ₃和C ₄的比例木炭样品中的生物量，但尚未与木炭形态分析一起广泛应用。使用碳同位素分析，我们证明了C ₃莎草可助长炭燃烧，其中C ₄没有草。这些结果挑战了普遍的假设，即细长木炭主要或仅来自草木，因为大多数证明这种关系的实验研究是在粒状（类草状）对可用燃料没有显着贡献的环境中进行的。反过来，这使对火记录中的木炭的长宽比的简单解释变得复杂，这超出了将温带森林与草原区分开来的环境中草比例的直接代理。迄今为止，在分离来自不同类香精类型的木炭方面所做的工作很少，未来的研究将受益于在火灾记录中区分包括禾本科和莎草科在内的类香精的能力。