I'm making a flower border where my veg patch was, and it has a lovely beech tree growing in it. The area around the tree is quite damp in winter because the overflow from a rain butt empties into the soil. It's south facing so dry in summer. So I thought a good use for the area would be a woodland glade. I've ordered native bluebells, wood anemones and fritillaria meleagris, and bought some ferns. I've numerous rough lumps of local limestone which I'm going to place in a circle round the tree to define the space. Is there anything I can do to encourage mosses, liverwort, lichens and fungi on the soil and stones?