Soil temperatures during prescribed burning and the occurrence of Rhizina undulata Fr

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Rhizina undulata is a postfire fungus. The ascospores germinate after heating over 35°C. The prescribed burning of one forest compartment was done in the purpose to investigate the effects of forest fire to atmosphere at Hyytiala Forestry Field Station in Southern Finland. The soil temperature measurements were one part of that research. One year after burning, the ascocarps of R. undulata appeared offering the possibility to use temperature data for studying the ecology of the species. The soil temperature was measured with 21 iButton sensors. Before and during the burning, all sensors were at 7 cm depth in the burned area. After burning, 10 sensors were moved to the unburned control area. The ascocarps were inventoried from 40 systematically located 10 m2 plots. On average 6 ascocarps were found in one plot. Ascocarps were present on 75% of plots. Most ascocarps were found on spots for seeding with bare mineral soil visible. The fungus has not killed germlings of pine but 43% of planted seedlings were dead. The temperature during the burning reached 35°C in 10 points. In 4 points, the temperature was over 60°C, which could be too high temperature for spores to survive. It seems that the ascospores could exist in the soil in 2 to 10 cm depth if they can germinate. The temperatures after burning did not reach 35°C in 7 cm depth. More measurements are needed to show if the temperature in the surface of burned area reached critical point after burning. Key words: Postfire fungus, forest fire, ascocarps.