Lichen inventory and visitor use study: Lava Beds National Monument

Siskiyou BioSurvey, LLC

doi:10.36967/2299861

Cave entrances in dry ecosystems provide important habitat for lichens because lichens are sensitive to environmental conditions at a fine scale and caves provide mesic, mild microclimates in otherwise harsh landscapes. The lichens associated with cave entrances at Lava Beds National Monument (LABE or the Monument) represent a unique floral component for the region and include many rare or little-known species. Despite the unique natural value of these communities, the impacts of visitor use on the lichens associated with the caves at the Monument are not fully known. The purpose of this study is to explore the effects of visitor use of caves and other ecological drivers on lichen communities at the Monument and provide managers with insight into this unique vegetation component. Our goal was to sample lichen communities that are representative of the diversity of caves that occur at the Monument. We ultimately sampled 42 of the 80 selected caves, prioritizing sites that could be accessed relatively easily (e.g., within approximately two miles from roads) to ensure a large sample size. A total of 211 lichen taxa were observed in this study, 27 of which were new records for Lava Beds National Monument. Our observations, in combination with a recent checklist of lichen species from the Monument, bring the total number of lichen taxa known from the Monument to 288. The richness of lichen species in the 42 one-acre plots we sampled surrounding cave entrances ranged from 15 to 97 (mean 59 species). Our study highlights that caves provide important habitat for lichens amid the semi-arid landscape of Lava Beds National Monument. Caves with deeper entrances and larger sink areas provide stronger microclimates, which in turn support more diverse lichen communities. Ice caves represent specialized habitats that host many rare or disjunct lichens. Larger and deeper caves may also provide better refugia from wildfire; almost all our study sites burned in the two years prior to sampling, but caves with deeper entrances and larger sink areas experienced a smaller amount of burned area in the immediate surroundings. Although visitor use has the potential to disturb lichens and cause localized species extirpations, we found no differences in lichen richness at the plot scale among caves that experience high and low visitor use. These findings suggest that existing visitor infrastructure, such as railings and stairways, may be effectively mitigating visitor impacts, at least at the landscape scale.

Lichen inventory and visitor use study: Lava Beds National Monument

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