Fungi are a common component of terrestrial ecosystems, although their preservation as molecular fossils is relatively rare. Saccharides, such as arabitol, mannitol and trehalose, are important in biochemical processes, and are the dominant compounds in fungi, lichens and yeasts. Here we present gas chromatography–mass spectrometry (GC–MS) analysis of fungal saccharides in brown coal extracts and compare their distribution to extant white, brown, and soft-rot fungi. Distribution differs depending on the type of decay in modern and fossil wood-decomposing fungi. An arabitol/(arabitol + trehalose) ratio higher than 0.6 for extant and fossil fungi is diagnostic for soft and brown rot, while values below 0.4 are characteristic of white rot fungi. Values between 0.4 and 0.6 suggest a mixed origin of fungal saccharides. The observed differences may shed light on the type of fungal activity, in particular relatated to climatic conditions of the Cenozoic.

We conclude that saccharides can be good indicators, sensitive to climate change, of wood degradation by fungi in thermally immature organic matter. As a case study, early Cenozoic lignites were formed on low latitudes in the tropics during or near the Paleocene/Eocene thermal maximum, as extant soft rot fungi can withstand extremes of temperature and humidity. The presence of these fungi is confirmed by the dominance of arabitol over trehalose in most of the Lower Cenozoic lignites and arabitol/(arabitol + trehalose) ratio values higher than 0.6. In contrast, Miocene detritic coals, which were formed in temperate to subtropical climates, contain saccharides derived from a mixture of different fungi with white rot predominance.

真菌是陆地生态系统的常见组成部分，尽管它们作为分子化石的保存相对罕见。糖类，如阿拉伯糖醇、甘露醇和海藻糖，在生化过程中很重要，并且是真菌、地衣和酵母中的主要化合物。在这里，我们对褐煤提取物中的真菌糖进行了气相色谱-质谱（GC-MS）分析，并将其分布与现存的白色、棕色和软腐真菌进行了比较。分布根据现代和化石木材分解真菌的腐烂类型而有所不同。对于现存和化石真菌来说，阿拉伯糖醇/（阿拉伯糖醇 + 海藻糖）比率高于 0.6 是软腐真菌和褐腐真菌的诊断指标，而低于 0.4 的比率是白腐真菌的特征。0.4 和 0.6 之间的值表明真菌糖的混合来源。

我们得出的结论是，糖类可以成为热未成熟有机物中真菌对木材降解的良好指标，对气候变化敏感。作为一个案例研究，早期新生代褐煤是在古新世/始新世热最大值期间或附近形成于热带低纬度地区，因为现存的软腐真菌可以承受极端的温度和湿度。在大多数新生代褐煤中，阿拉伯糖醇相对于海藻糖占主导地位，并且阿拉伯糖醇/（阿拉伯糖醇+海藻糖）比率值高于0.6，这证实了这些真菌的存在。相比之下，在温带至亚热带气候中形成的中新世碎屑煤含有来自不同真菌混合物的糖类，其中以白腐病为主。