Here's why:

* Low temperatures: Tundras experience extremely cold temperatures for most of the year, with average temperatures below freezing for at least six months.

* Permafrost: The defining characteristic of the tundra is the presence of permafrost, permanently frozen ground that lies just below the surface.

* Limited plant species: Due to the harsh conditions, only a limited number of plant species can survive in the tundra, primarily low-growing shrubs, grasses, and mosses.

Let me know if you'd like to know more about the tundra!