Mosses and liverworts (collectively known as bryophytes) are non-vascular plants, meaning that they lack the inner tubes that move water throughout them like other plants with roots, stems, and leaves. Instead, they absorb water more like a paper towel, and can live dry for a long time without dying.
Bryophyts are also unique in their ability to reproduce sexually. This is done by the moss producing spores, which grow into gametophytes. These then produce eggs or sperm, and finally the eggs and sperm fuse to create a zygote for a new plant. There are both male and female mosses, although some have both types of sex organs within the same plant.
Mosses thrive on the wet Alaskan tundra, where they draw nutrients and water from the shallow ground. In addition, because they are so small, low-growing, and have a slow metabolism, they can make it through the harsh arctic winters that limit the range of so many other species.
Because there are around 1,300 known species of mosses in the US, and most are extremely tiny and similar-looking, they can be incredibly hard to identify. Some of the more common species you will find around Bering Land Bridge include Sphagnum (peat mosses), Aulacomnium (bog mosses), Dycranum (wind-blown or forked mosses), polytrichum (haircap mosses), and Rhizomnium.