In areas of permafrost, stands of black spruce are frequently observed in the landscape, while other tree species are noticeably absent. Often these stands are referred to as "drunken forests" because many of the black spruce often "lean over" (that is, they are displaced from their normal vertical alignment). What is the most likely explanation for the unusual growth of these forests in this marginal habitat?

Answer: this is due to failure to develop tap roots, but rather shallow roots beds because of the the frozen soil

Any area of land with temperature of 0 - degree completely frozen, is called permafrost. Thus penetration of root for support and trapping of water is reduced and nearly impossible. Therefore such plants (black spruce) failed to penetrate the frost with the tap roots to gain needed support, rather they maintain support through the shallow roots beds, preventing them from attaining the usual upright position, making them to bend., thus the name drunken forest, like a drunken individual who can not maintain an upright position.