Spruce is one of the most species-rich genera among the conifers. There are a total of around 50 different species that are distributed around the globe in the temperate to subpolar zone of the northern hemisphere. Like hardly any other tree species, spruces have adapted to the polar climate and occur naturally in the temperate zone almost exclusively in the cold mountain regions. North of the Arctic Circle they often form pure stands and are therefore the most important trees of the so-called boreal coniferous forest. Most spruce species, however, come from the high mountains of western and central China.