The back of a silver birch. The horizontal lines are lenticels, pores in the bark which allows for gas exchange. You find these all over the tree and covering them up (by planting too deep or raising the soil level) is bad thing to do. You should always plant to the same depth as it was planted in the nursery.
Birch are a hardy species and are also a pioneers species, they are the first to colonise bare land, derelict sites and brownfield sites. They provide habitat for numerous species and allow enough light through the canopy for shrubs to develop. Because of this birch trees are great for phytoremediation (removing chemicals & heavy metals from soils, usually on brownfield sites)