The main soil order associated with the taiga is spodosol . Sphagnum moss forms a spongy mat over ponded water. Growing on this mat are species of the tundra such as cottongrass and shrubs of the heath family. Black spruce and larch ring the edge. These are low nutrient, droughty substrates not tolerated by spruce and fir.
Larch forests claim the thin, waterlogged substrate in level areas underlain with permafrost.
These forests are open with understories of shrubs, mosses and lichens. In Alaska stands of Larix larichina are localized phenomena, but in Siberia east of the Yenesei River the extreme continentality and nearly continuous permafrost give rise to vast areas dominated by Larix dihurica . The mammalian herbivores on which they feed include the snowshoe or varying hare, red squirrel, lemmings, and voles. Among birds, insect-eaters like the wood warblers are migratory and leave after the breeding season. During poor cone years, normal residents like the evening grosbeak, pine siskin, and red crossbill leave the taiga in winter and may be seen at bird feeders here in Virginia.