I suspect several things going on here. The big SD-2 type circles look to me like old water retention basins, probably for sheep or to attract wildlife or something.

The small light circles with dark dots are undoubtedly plants, probably creosote. The light areas are the root zone where other plants cannot compete for the water. Larger creosote bushes form dark rings of clone plants when the center plants die out. The oldest living things known are creosote rings, where all of the plants in the ring are genetically identical and have been living for many thousands of years.

The darker circles in runoff areas are probably also some kind of plant colony.

-Tim