At first glance, grit crusts are typical of what researchers call biological soil crusts, or “biocrusts,” a community of coexisting bacteria, fungi, algae, and other microbes that cover the soil in a coherent sheet. It may look like a typical example. About 12 percent of the Earth’s land area is covered by a biological crust. Ecologists often refer to these colonies as the Earth’s “living skin.”
Over the past century, scientists around the world have identified biocrusts and worked to understand their role in shaping ecosystems. They learned that the crust holds soil particles in place and provides essential nutrients such as carbon, nitrogen and phosphorus to organisms growing in that soil. In 2012, Budel and his colleagues Estimate Biocrust absorbs and recycles about 7 percent of all carbon and nearly half of all nitrogen chemically “fixed” by terrestrial plants. The role of biocrust in sourcing digestible nitrogen is particularly important in arid deserts. In other regions, lightning often converts atmospheric nitrogen to nitrates, but thunderstorms are rare in the desert.
Said biocrust creates a ‘little oasis of fertility’ Jane Belknapan ecologist with the U.S. Geological Survey, who helped standardize the term “biological crust” in 2001. [like] Popsicles for soil organisms. They are sugar addicts like all of us. “
But Pan de Azucar’s microbial community is more than just an old biological crust. Traditional biocrust overlies the top layer of fine soil particles, and other types of organisms sprout directly onto individual rocks, but “the sand grains are in between, which are transition zones,” he said. Liesbeth van den BrinkAn ecological researcher at the University of Tübingen, he currently lives with Gutierrez Alvarado in the outskirts of Pan de Azucar. In grit crust, the stone provides the structure, but the microbes colonize the stone in coherent sheets, like the thin layer of resin that grouts a rock garden together.
Living organisms are so closely related to the rocky substrate, he said, that the sand crust embodies “the clash of abiotic and living organisms.” Romulo Oses, a biologist at the University of Atacama. “This interface gives you a lot of answers.”
Pan de Azúcar’s sand mass forced scientists to: extend the concept What is the biological crust, where microbes can live, and how microbial communities shape the surrounding environment. They are opening the door to rethinking how Earth and life co-evolved over time.
sipping the mist
Pan de Azucar is dilapidated, but not lifeless. Near sea level and adjacent to the Pacific Ocean, the park is much warmer than the high altitude, ultra-arid heart of Atacama. Still, annual rainfall is no more than 12 mm, and solar radiation is often brutally high.
Gutierrez Alvarado, Van den Brink, and I can stop for local seafood empanadas on our way to the park’s only food truck. Gutierrez Alvarado stopped to check one of the weather-monitoring devices, surrounded by barbed wire and anchored in desert rock. Next to it, he pointed out a depression in the ground, about the size of a cow, where the guanaco, the llama’s wild relative, had recently taken a dust bath. Gutierrez Alvarado and other rangers recently counted 83 guanacos in the park.