The Stephen J. Barnhart Herbarium at Pepperwood houses specimens of fungi, lichen, and non-vascular and vascular plants collected at Pepperwood Preserve, Sonoma County, California. It includes plants collected by Greg deNevers who worked as the resident biologist for the California Academy of Sciences during the 1980s. The Barnhart Herbarium is under the supervision of the Preserve Ecologist and is primarily staffed by volunteers and community scientists, who are involved in the collection of plant specimens and the curation and maintenance of the Herbarium.