Authors: Dana Carpenter; Dr. Joseph O'Brien; Dr. Nina Wurzburger; Derek Wallace; Ellie Fowler;Over the last 150 years, the forests of the southern Appalachians have shifted in vegetation composition due to a variety of causes including wildfires and fire exclusion. Fire exclusion has been identified as a driver of forest mesophication, where anisohydric species (e.g. oaks) decline while isohydric species (e.g. maples) increase. We propose that litter characteristics and mycorrhizal symbionts of the two water use strategies act as a mesophication positive feedback. Oak litter while conducive to carrying fire, is also resistant to decomposition and oaks are associated with ectomycorrhizal symbionts that are less efficient decomposers. As a consequence, an O horizon (duff layer) is more likely to form in areas dominated by oaks. Should a wildfire occur after decades of fire exclusion, high post-fire mortality would be expected due to the consumption of duff and the subsequent root damage. Alternatively, in areas dominated by isohydric species, their more labile litter and arbuscular mycorhizzae symbionts result in little duff formation and less post fire mortality. We are testing this hypothesis within the perimeter of the Rock Mountain fire that occurred the Chattahoochee-Oconee and Nantahala National Forests in November 2016. We report initial findings on patterns of duff formation, consumption and initial mortality estimates.
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