Evidence that pyrophilous fungi aggregate soil after forest fire
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Forest fire is an important occurrence in western landscapes where it helps drive ecosystem processes, and prescribed fire is a common forest management strategy. An initial consequence of fire is burned ground with reduced biodiversity. Numerous studies have documented how forests recover after fire in terms of plant regeneration and animal colonization, but little is known of the ecological roles fungi play in this process. Pyrophilous (burn-loving) fungi are documented to reliably produce large fruitings and copious mycelium on burns after fire in North America, Europe, Asia, and Australia. We hypothesize that pyrophilous fungi help bind and stabilize soil after forest fires via their extensive mycelial network. Three pyrophilous fungi, Geopyxis carbonaria, Pyronema omphalodes, and Morchella septimelata were tested for their ability to aggregate burned soil. The fungi were isolated from burn sites, grown in vitro, and inoculated onto sterilized soil from a natural burn. The ability of each species to aggregate soil in comparison to non-inoculated controls was assessed after 10, 20, 30, and 40 days, using a wet sieve aggregate stability test. All three fungi increased soil aggregation after 10 days, and this increase was maintained for the 40-day period. The burned soil was up to 30% more aggregated when a fungus was present; results provide the first direct evidence that pyrophilous fungi aggregate burn soil. This further implies that these fungi play a role in reducing soil erosion and enhancing soil moisture soon after fire in burned forests. Pyrophilous fungi also decompose charred material, sequester carbon, and capture transient nitrogen pulses after fire. This overlooked group of fungi may be critical in enhancing conditions for plant regeneration after forest fire at an early stage in recovery. Consideration should be given to avoiding or delaying restoration activities that disturb this natural process, especially those that contribute to soil compaction, during early post-fire recovery when these fungi are proliferating.
Filialuna, Olivia, and Cathy Cripps. “Evidence That Pyrophilous Fungi Aggregate Soil after Forest Fire.” Forest Ecology and Management 498 (October 2021): 119579. doi:10.1016/j.foreco.2021.119579.