STABLE ISOTOPIC SIGNATURES OF ENDOMYCORRHIZAL FUNGAL SPORES AT ELEVATED TEMPERATURES: APPLICATIONS TO ARCHAEOLOGY

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in the soil system as symbionts to a multitude of plant root systems. Through the course of geologic time, fungal spores have been present in terrestrial sediments as far back as the Early Devonian. Prior research on organic material in soils reveals that a near complete loss of carbon and organic matter occurs in soils when exposed to temperatures above 400°C. However, additional work on these soils has shown several species of AMF to be structurally resistant to temperatures up to 500°C, despite the loss of all other organic structures. From a geological and archaeological prospective, we are interested in investigating the progressive chemical changes of these spores at increasingly high temperatures to determine whether they may be useful as a “post fire thermometer”. Initial investigations of changes in δ¹³C and δ¹⁵N signatures of Acaulospora, Gigaspora, Glomus, and Scutellospora spores at increasing temperatures shows an abrupt shift toward heavier values for both isotopes above 300°C and 250°C respectively. This correlates with large losses in %C and %N mass at these temperatures and likely represents the loss of specific organic compounds at progressively high temperatures.