I believe they are relatively hard to move, but I'm not a solar expert by any stretch (though it's a different story when it comes to soil).

Somewhat related: putting panels on reclaimed tailings ponds or waste rock dumps is a good idea, in that usually these have an engineered cover (rock/soil/LDPE) That limits rooting depth (don't want plants reaching what we are trying to protect [toxic waste]) so we plant grasses and shit rather than trees. Grasses + panels is the best of both cover stability and green energy