For most of the year, the mycelium in the volcanic ash of Oregon’s Cascade Range lurks quietly underground, waiting for just the right conditions to start pushing out matsutake mushrooms. When fall arrives, droves of foragers—largely a mixture of 70s-era counterculture types, South East Asian immigrants and Latino migrant workers—spend a few months collecting the prized fungus. Foraging is a difficult job; matsutakes grab particularly high prices before their caps are fully open, so hunters search for what Seattle-based photographer Eirik Johnson calls “the subtlest welt” on the forest floor. They sell them to roadside vendors, who overnight them to Tokyo, where a single specimen can sell for $100. (The aromatic matsutake, which means “pine mushroom,” grows in Japan. But the demand for it—which famed mycologist David Arora described as smelling like a mix of Red Hots and sweaty socks—vastly outstrips national supplies.) Like the mushrooms, these foragers appear and disappear quickly, returning each year to skeletal structures they’ve built out of branches and wrapped in tarps to create makeshift shelters. It’s these structures, in which foragers rest from the hunt and socialize, that intrigued Mr. Johnson, whose series “Mushroom Camps” opened last weekend at the Bolinas Museum. In a chat with the Light, Mr. Johnson described seeing “the outline of homes of tree branches. They were beautiful, strange and beautiful, bathed in the golden light of the pine forest.” The series includes five large-scale photographs and a digital slideshow of a much wider selection of pictures that document the economy and tightknit communities that revolve around the matsutake. One year, a Laotian pop star performed in a forest camp; another time, a Buddhist monk blessed the season. In the Tokyo auction houses Mr. Johnson visited, mushrooms are often packaged in cardboard boxes screen-printed with wood grain and filled with ferns to evoke the mushrooms’ origins. In one photograph, the bone-like branch of a forest shelter is tied to four pine trees in a luminous scene, seemingly waiting for the cyclical return of the seasonal inhabitants. The exhibit shows through June 12.