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Soil fungi recover slowly following high-severity wildfires

Date: August 21, 2019

Belowground ectomycorrhizal fungi that connect with tree roots and their fruiting bodies, called sporocarps (or mushrooms), are slow to recover in severely-burned ponderosa pine forests


High-severity edge plots were established adjacent to forest edges, and high-severity interior plots were established at least 200 m from any live tree
12 4-hectare plots were established. High-severity edge plots were established adjacent to forest edges, and high-severity interior plots were established at least 200 m from any live tree.

Background

In recent decades, wildfires in ponderosa pine forests have increased in size and severity. These wildfires can remove large, contiguous patches of mature forests, alter dominant plant communities and increase woody debris, potentially altering fungal community composition. Additionally, post-fire conditions may shift dominant fungal functional groups from plant-symbiotic ectomycorrhizal fungi to more saprotrophic fungi.

Research

We investigated the long-term (13 years post-wildfire) effect of fire severity on 1) fungal sporocarp density, functional groups and community composition and 2) ectomycorrhizal colonization and community composition from naturally regenerating ponderosa pine seedlings on the Pumpkin Fire that burned in 2000 in Arizona, USA. Plots were located in unburned areas, moderate-severity burned areas, and two high-severity (defined as 100 percent tree mortality) burned areas. High-severity burned areas were established either adjacent to residual live forest edges, or at least 200 meters from any residual live trees.

Key Findings

  • 13 years after a wildfire, regenerating pine seedlings in areas where all the trees were killed had fewer ectomycorrhizal species associated with their roots.
  • High severity burned areas also had fewer species and densities of ectomycorrhizal sporocarps compared to moderately-burned or unburned areas.
  • These results suggest that some species of soil fungi are either resilient or recovering in areas where all the trees were killed, but fungal density and community composition could be limited for some time, likely from dispersal constraints and a lack of mature tree hosts.

Additional Resources

Owen, S.M. 2019. Tree regeneration following large wildfires in southwestern ponderosa pine forests. Ph.D. Dissertation, Northern Arizona University.

Owen, S.M., A. Patterson, C.A. Gehring, C.H. Sieg, L.S. Baggett, P. Z. Fulé. In review. Large, high-severity burn patches limit fungal recovery 13 years after wildfire in a ponderosa pine forest. Soil Biology and Biochemistry.



External Partners: 
Adair Patterson, Northern Arizona University
Catherine Gehring, Northern Arizona University
Pete Fulé, Northern Arizona University
Research Location: 
Arizona