insert into control.lua between line 449 and 450 (right after "if r then"):
                if r == 'dead-tree' then
                    tile_type = surface.get_tile(e.position).name
                    if string.find(tile_type, "sand") or string.find(tile_type, "desert") then r = 'dead-tree-desert'
                    else r = 'dead-grey-trunk'
                    end
                end
Haven't managed to get the "desert" path to trigger yet, so it's not fully tested.