Here's why:

* Dense short vegetation: Tundra is known for its low-lying, dense vegetation consisting of mosses, lichens, grasses, and dwarf shrubs.

* Very few trees: The harsh conditions of tundra, including permafrost (permanently frozen ground), short growing seasons, and strong winds, make it difficult for trees to grow.

While other biomes can have some similar characteristics, tundra is the most definitive answer due to the combination of dense short vegetation and the near absence of trees.