This sensor operates at a single frequency of 50 MHz Two modes of measurement were performed: (1) the sensor was inserted directly into the dune crust, where sand is exposed at the surface, to the encrusted surface of the dune slopes, and to the same spots on the slope following the removal of the biocrusts covering the top few mm of the dune surface; (2) sand from the dune crest and crumbled biocrusts from the dune slopes were measured in a 1 L glass jar.