Abstract Severe wildfires combust most above ground vegetation and detritus layers, altering the content and chemical composition of soil organic matter (SOM). To evaluate the lasting effects of wildfire on SOM and the recovery of burned soils, we sampled surface (Oa horizon) and mineral soils (0−5 and 5−15 cm depths) in unburned areas and areas burned at moderate and high severity 14 years after the 2002 Hayman Fire, in Colorado, USA. We characterized SOM using Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC–MS) and identified 106 pyrolysates within eight chemical classes [aromatic hydrocarbon (ArH), carbohydrate (Carb), lignin compound (LgC), nitrogen containing compound (Ntg), polyaromatic hydrocarbon (PAH), phenol compound (PhC), saturated hydrocarbon (SaH), and unsaturated hydrocarbon (UnSaH)]. Burned soils had greater total quantified peak areas (TQPA) for the pyrogenic C indicator (PyC) benzene, compared to unburned soils; however, other common PyC markers were not abundant in burned relative to unburned soils. Factor analysis on the individual pyrolysates suggests that factors 1 and 2 correlated with pyrolysate aromaticity and hydrophobicity, respectively. Sample factor scores potentially suggest that SOM aromaticity increases with fire severity, though difference between moderate and high severity was slight. Factor analysis also indicates that the ratio of [ArH + Ntg] / [PhC + LgC] may serve as index of PyC content in SOM. This study shows that wildfire effects on SOM character may persist for more than a decade of ecosystem recovery and that Py-GC–MS coupled with factor analysis has utility for evaluating how disturbance alters SOM and PyC in complex environments.

中文翻译：

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野火后 14 年土壤有机质的特征：热解-气相色谱质谱 (Py-GC-MS) 研究

摘要 严重的野火燃烧了大部分地上植被和碎屑层，改变了土壤有机质 (SOM) 的含量和化学成分。为了评估野火对 SOM 和燃烧土壤恢复的持久影响，我们对未燃烧区域和中度和高度燃烧区域的表面（Oa 层）和矿质土壤（深度 0-5 和 5-15 厘米）进行了采样 14 年2002 年美国科罗拉多州海曼火灾之后。我们使用热解气相色谱质谱 (Py-GC-MS) 对 SOM 进行了表征，并鉴定了八种化学类别中的 106 种热解产物 [芳烃 (ArH)、碳水化合物 (Carb)、木质素化合物 (LgC)、含氮化合物 (Ntg)、多芳烃烃 (PAH)、酚类化合物 (PhC)、饱和烃 (SaH) 和不饱和烃 (UnSaH)]。与未燃烧的土壤相比，燃烧的土壤具有更大的热解 C 指示剂 (PyC) 苯的总量化峰面积 (TQPA)；然而，相对于未燃烧的土壤，其他常见的 PyC 标记在燃烧的土壤中并不丰富。对单个热解产物的因子分析表明因子 1 和因子 2 分别与热解产物的芳香性和疏水性相关。样本因子得分可能表明 SOM 的芳香性随着火灾的严重程度而增加，尽管中度和高度之间的差异很小。因子分析还表明 [ArH + Ntg] / [PhC + LgC] 的比率可以作为 SOM 中 PyC 含量的指标。