bark brown garden natural nature ornamental patterned shiny smooth tree abstract betula pendula bumps dashes deciduous gray grey raised short stripes silver birch silver birch tree texture textured tree trunk uneven appearance background bare cambodian close-up colors colours cracked dry edge edges lines mottled pitted rough shapes sunlight surface surfaces textures tree-trunk trunk variations wallpaper wood Australian cracks eucalypt eucalypts layers shadows white backgrounds patterns ridges shades of colour strips varieties