Here's why:

* Gelisols are a soil order characterized by permafrost, a layer of permanently frozen ground.

* Tundra biomes are found in extremely cold climates with permafrost, making Gelisols the dominant soil type.

These soils are very young, nutrient-poor, and have a slow decomposition rate due to the cold temperatures. They are also often waterlogged because of the permafrost layer, which prevents drainage.