We are talking about Hort's reply 60 image of t...

We are talking about Hort's reply 60 image of the MECA OM aren't we? The OM has a field of two square millimeters.
The sample has been dug out, mixed in handling, vibrated onto the substrate, scraped leaving a particle maximum height of 200um and the substrate has been moved vertical to image. It is hard to see how the sublimating ice rind theory would be applicable with this preparation and at this scale, although it would certainly be a contender for a similar phenomona for an undisturbed soil surface at the macro scale.

The substrate itself has varying grids and hole patterns that would possibly give the illusion of lines when the sample is distributed..