Here's why:

* Gelisols are characterized by permafrost, a layer of soil that remains frozen for at least two years. This permafrost restricts drainage and limits plant growth.

* Tundra environments are known for their cold temperatures and permafrost, making Gelisol the dominant soil type.

While Gelisol is the primary soil type, other soil types can exist in the tundra, but they're less common.