Relationships of current and past anthropogenic disturbance to mycorrhizal sporocarp fruiting patterns at Crater Lake National Park, Oregon

Intensive recreational use of subalpine forests can create localized areas of concentrated disturbance where vegetation is altered, soils compacted, and surface fuels depleted. Many aspects of this disturbance type have been studied, but no research has focused on the effects of recreational use on mycorrhizal fungus sporocarp production. We measured the effects of recreational land or site use on soil properties and fuel levels and related these attributes to mycorrhizal fungal sporocarp production at Crater Lake National Park, Oregon. Control and disturbed sites differed significantly in soil bulk density, 15N enrichment, and fuel levels, but not in total fungal collections or species diversity at the macrosite scale. Our sampling methods were not designed to quantify the effects of anthropogenic disturbance on fungal fruiting patterns at the microsite scale, but fungal productivity was markedly reduced in the most disturbed microsites. Within the disturbed units, the paucity of fungi collected in highly disturbed microsites was offset by the abundance and diversity of mycorrhizal fungi collected in protected microsites. Many fungal species did not differ significantly in fruiting patterns or in preferences between sites or treatments at the macrosite scale, but several indicator taxa were identified.