What group of plants are best adapted to live in regions where the layer of soil beneath the surface stays frozen all the time?

The group of plants best adapted to live in regions where the soil beneath the surface remains frozen year-round is known as "permafrost-adapted plants," which include various types of mosses, lichens, and low-growing shrubs. These plants have developed unique adaptations, such as the ability to photosynthesize at low temperatures and a short growing season, allowing them to thrive in harsh Arctic and alpine environments. Their root systems are shallow to avoid the frozen layer and maximize nutrient uptake in the limited thawed soil.