A visit to a hobby shop which stocks model railroad supplies will have what you need. Just add some white glue and SHAZAM!! you have it
Woodland Scenics tree forms can be quickly adapted (=mutilated) to provide blasted trees. Just leave off the greenery.
While at the hobby store, you can get plastic sheet and structural shapes to make movement trays. The structural shapes can form a rim around the sheet. PlastiStruct is the brand name. Ground cover for grass, weeds,rocks, and other stuff
A bit of spray pain to fit in with your playing surface and it is job done!