Abstract Detail

Mycological Section

Nelsen, Matthew P. [1], DiMichele, William A. [2], Peters, Shanan [3], Boyce, C. Kevin [1].

Re-assessing the role of fungi and lignin in coal formation.

Coal is often thought of largely as a product of the accumulation and diagenetic alteration of the plant cell wall polymer lignin. Lignin occurs in all vascular plants, primarily in tissues that provide hydraulic transport, structural support, and/or defense against pathogens and predators. Cellulose is more abundant than lignin—although lignin nonetheless accounts for approximately 30% of the organic carbon in modern ecosystems and soils—however cellulose is more subject to decay, so that lignin is thought to be the dominant contributor to organic accumulation over geologic timescales. While coal is known from the Early Devonian, Carboniferous-Permian deposits are the most abundant, geographically extensive, and economically important. The temporal lag between the evolution of abundant lignin production in woody plants (in the later Devonian and Carboniferous) and lignin-degrading fungi (toward the end of the Carboniferous) is thought to have resulted in vast accumulations of decay-resistant, lignin-rich plant material, which ultimately contributed to the formation of Carboniferous coal. However, we argue that geochemical, depositional and biological data are inconsistent with such a model. Many Carboniferous coal formations are composed largely of periderm from arborescent lycopsids, which previous organic geochemical work has found to be unlignified and more likely dominated by a suberin-like biopolymer. Consequently, the presumed evolutionary delay of lignin-degrading fungi would have been of minimal relevance to the decomposition of these suberin-rich tissues. Indeed, the relative abundance of organic rich sediments in the record of North America indicates similar accumulation rates before, during, and after lycopsid dominance punctuated by a short, sharp peak in deposition during the later Carboniferous that is not consistent with an evolutionary explanation. Finally, we discuss the lignin-degrading capacity of fungi found outside Agaricomycetes, and their implications for the evolutionary origins of lignin degradation. We suggest that Carboniferous coal deposits were not a result of increased lignin synthesis and the delayed evolution of fungal lignin degradation, but were instead formed through a combination of climatic and tectonic factors.

1 - Stanford University, Geological and Environmental Sciences, 450 Serra Mall, Building 320, Stanford, CA, 94305, USA
2 - Smithsonian Institution, Dept Of Paleobiology, NHB MRC 121, Washington, DC, 20560-0001, USA
3 - University of Wisconsin-Madison, Department of Geoscience, 1215 W. Dayton Street, Madison, WI, 53706, USA

Keywords:
Carboniferous
Fungi
lignin
wood decay fungi.

Presentation Type: Oral Paper:Papers for Sections
Session: 29
Location: Salon 1/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 9:30 AM
Number: 29007
Abstract ID:1346
Candidate for Awards:None