What is a Moss?

Mosses are part of a group of plants called bryophytes. Bryophytes include mosses, hornworts and liverworts. They evolved from green algae around 540 million years ago. This early environment can explain a lot of the characteristics of bryophytes today:

• Byrophytes evolved from simple, early species that were used to being submerged in water, so they don’t have good systems for storing or distributing water- they lack vascular systems. This is partially why you find mosses thriving in very wet regions, though they do exist in a broad range of environments today.  
• Mosses can be found on a variety of different habitats, including tree trunks, organic matter and rocky substrates. They can survive on rocky habitats because:
• (1) Most bryophytes are poikilohydric: they can go dormant (stop photosynthesizing) when it is dry out. 
• (2) Bryophytes lack traditional root systems; instead, they have structures called rhizines. Rhizines are primarily there to attach the moss to its habitat, so unlike many other plant groups, many mosses take in their nutrients from the air around them and water flowing over them. In fact, they absorb water directly into their cells.

Mosses reproduce differently than most other plants:

• They reproduce via spore production, and rely on wind or water for dispersal.
• Modern-day ferns, who also reproduce via spore production, evolved from early mosses.
• Mosses can also reproduce asexually, via shoots. 

Mosses play an important role in the ecosystems of the Pacific Northwest:

• They increase the soil's water and nutrient capacity, as well as work to prevent soil erosion.
• They interact in the carbon and nutrient cycles, making them good indicators of both air and water pollution
• Certain birds and mammals (like the threatened marbled murrelet) use mosses for nesting material. Other organisms rely on mosses as a food source.

Sources: (1), (2)

Sources: (1), (2), (3)