For this Pensive Tuesday, I'm once again ruminating on the subject of dirt. Desert dirt, specifically. I've spent long stretches of time hiking through the desert on archaeological digs, and for other assorted reasons. The hard crust of desert soils has always intrigued me. What makes that crunchy crust? When that crust is disturbed, for instance, by vehicles, dust storms can erupt. And plants can no longer live there. So what is it about the crust in which so many Mesembs and cacti live?
Cyanobacteria.
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| Cyanobacteria (photo Wiki Commons) |
They are so ancient, these little guys, that they have been around for practically all of Earth's history. They grow into vast collectives that stabilize soils, fix nitrogen, provide oxygen, and prevent erosion in arid and semi-arid environments. They make it possible for plants and animals to colonize harsh environments. When they are destroyed, the soil is no longer hospitable to other plants and the animals that feed on the plants. Amazing!
Climate change is having an effect on these critters, but we don't know much about it yet. The main species that grows in hot deserts, Microceleus steenstrupii, should do fine for a time, but other species, equally important to the environment, might not. Hopefully, scientists are doing more research to find out what's going on in those crusts. And when you're walking over a soil crust, be sure to thank the tiny creatures that make it possible!
