S. caninervis, the most common moss in the Mojave Desert, spends most of the year parched and brown — in a state of suspended animation awaiting the next rain. “It is something only a mother can love,” Dr. Mishler said. But the mosses are long-lived; a single clump could easily be a centenarian.
Although S. caninervis made up more than two-thirds of the hypolithic moss at Wrightwood, the researchers identified another species, Tortula inermis. That moss typically grows at lower, hotter elevations, but was able to thrive at the Wrightwood site, seeming to rely on the quartz for protection from the cold.
These quartzite oases, while common at Wrightwood, only emerge in what Ms. Ekwealor called a “goldilocks” situation. If the quartz is too tiny, it will be too easily windswept to let anything grow underneath. If it is too large or opaque, not enough light will shine through for photosynthesis. If it is too clear, it could become a miniature greenhouse and capture even more heat. The quartz needs to be just right: around an inch thick and milky enough to transmit up to 4 percent of incident light.
But the vastness of the desert and the abundance of pebbles means that serendipity can become commonplace, Ms. Ekwealor said: “It’s low probability, but lots of opportunity,” she said.
The study highlighted the importance of microenvironments that may be invisible to the human eye, Ms. Ekwealor added. Dr. Warren-Rhodes noted that hypolithic communities, tiny as they are, affect carbon cycling and soil conservation.
After presenting this research at several conferences, Ms. Ekwealor said she now receives sporadic texts from people identifying hypolithic mosses across the country. “I hope people start flipping rocks to see what else is out there,” she said. After a pause, she added, “And gently placing them back down again, so the moss can survive.”