Recovery of soil fungi following fire

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In the Deschutes National Forest, researchers with the USFS Pacific Northwest Research Station, Oregon State University, and Kansas State University conducted a study to compare the effects of low-intensity and high-intensity burns on soil organisms and nutrients. The high-intensity burns were simulated by burning “mega-logs,” a proxy for naturally occurring large downed wood. They established 12 sites and collected pre- and postburn soil samples and continuous temperature recordings during the fire. As expected, the soil on the mega-log sites experienced intense heating. High temperatures penetrated 4 inches below the surface but no farther than 12 inches, and soil carbon and organic matterderived nutrients were volatized. There was also a substantial loss of nearly all the existing microbial communities. Within one week, however, fungi had returned; ascomycete fungi, such as morels, dominated the sites. Ponderosa pine seedlings were colonized by ectomycorrhizal fungi within four months.