Data from: Charcoal analysis for temperature reconstruction with infrared spectroscopy

The duration and maximum combustion temperature of vegetation fires are important fire properties with implications for ecology, hydrology, hazard potential, and many other processes. Directly measuring maximum combustion temperature during vegetation fires is difficult. However, chemical properties of charcoal formed as a by-product of fire reflect key chemical transformations associated with temperatures. Therefore, they could be used indirectly to determine the maximum combustion temperature of vegetation fires. To evaluate the reliability of charcoal chemistry as an indicator of maximum combustion temperature, we studied the chemical properties of charcoal formed through two laboratory methods at measured temperatures. Using a muffle furnace, we generated charcoal from the woody material of ten different tree and shrub species at seven distinct peak temperatures (from 200 °C to 800 °C in 100 °C increments). Additionally, we simulated more natural combustion conditions by burning woody material and leaves of four tree species in a combustion facility instrumented with thermocouples, including thermocouples inside and outside of tree branches. Charcoal samples generated in these controlled settings were analyzed using Fourier Transform Infrared (FTIR) spectroscopy to characterize their chemical properties. The Modern Analogue Technique (MAT) was employed on FTIR spectra of muffle furnace charcoal to assess the accuracy of inferring maximum pyrolysis temperature. The MAT modeltemperature matching accuracy improved from 46% for all analogues to 81% when including ±100 ℃. Furthermore, we used MAT to compare charcoal created in the combustion facility with muffle furnace charcoal. Our findings indicate that the spectra of charcoals generated in a combustion facility can be accurately matched with muffle furnace-created charcoals of similar temperatures using MAT, and the accuracy improved when comparing the maximum pyrolysis temperature from muffle furnace charcoal with the maximum inner temperature of the combustion facility charcoal. This suggests that charcoal produced in a muffle furnace may be representative of the inner maximum temperatures for vegetation fire-produced charcoals. FTIR spectroscopy is a promising tool for determining maximum fire temperature from charcoals of vegetation and prescribed fires and may have implications for fossil charcoal from palaeoecological records.

植被火灾的持续时长与最高燃烧温度是关键的火灾特性，其对生态学、水文学、灾害潜能及诸多其他相关过程具有重要意义。直接测量植被火灾过程中的最高燃烧温度颇具难度。然而，作为火灾副产物生成的炭的化学性质，可反映与温度相关的关键化学转化过程，因此可通过间接途径利用其推断植被火灾的最高燃烧温度。为评估炭化学性质作为最高燃烧温度指示物的可靠性，我们针对两种实验室方法下、于已知温度中形成的炭的化学性质开展了研究。其一，使用马弗炉（muffle furnace），以10种不同乔木与灌木物种的木质材料为原料，在7个梯度的峰值温度下（以100℃为间隔，从200℃至800℃）制备炭样品；其二，通过配备热电偶的燃烧装置，对4种乔木的木质材料与叶片进行燃烧，以模拟更贴近自然的燃烧条件，该装置包含树枝内外两处的热电偶。对上述可控环境下制备的炭样品，采用傅里叶变换红外（Fourier Transform Infrared, FTIR）光谱法进行分析，以表征其化学组成与性质。我们将现代类比技术（Modern Analogue Technique, MAT）应用于马弗炉制备的炭的FTIR光谱，以评估推断最高热解温度的准确性。结果显示，MAT的温度匹配准确率从仅使用所有类比物时的46%提升至纳入±100℃误差范围后的81%。此外，我们利用MAT将燃烧装置制备的炭与马弗炉制备的炭进行对比分析。研究发现，通过MAT可将燃烧装置制备的炭的光谱，准确匹配至温度相近的马弗炉制备的炭；且当对比马弗炉炭的最高热解温度与燃烧装置炭的内部最高温度时，匹配准确率进一步提升。这表明马弗炉制备的炭或可代表植被火灾生成炭的内部最高温度。傅里叶变换红外光谱法是一种极具应用前景的工具，可通过植被火灾与计划火烧（prescribed fires）产生的炭来测定最高火灾温度，该方法或对古生态学记录中的化石炭研究具有参考价值。