Magnificent Mosses

A Brief Natural History of an Ancient Soil Architect

By Summer Swallow, Environmental Educator

It’s springtime, and that means we get to see a beautiful array of vibrant green all around us. This annual greening is made up of all sorts of plants and lichens but one of the most splendid and archaic of this green wall is made up of Bryophyta, or mosses. Bryophyte is the name for nonvascular (meaning lacking channels for transporting water throughout the plant) and seedless plants. Today, bryophytes are represented by three phyla: mosses (Bryophyta), liverworts (Hepatophyta) and hornworts (Anthocerophyta).

Photo Credit Summer Swallow

Bryo means moss and phyte means plant, and these plants have been here for a long time. The first evidence we have of bryophytes appears in rocks collected from Argentina that date back to between 485 and 444 million years ago. Like most plants who have been around for a long time, these green marvels function a little differently from the more modern approach. Instead of a customary root system they have a root-like structure called a rhizoid, that provides anchorage to a substrate (rock, tree trunk, or your rooftop), but it is not a true root because it does not absorb water or nutrients. Instead, these rhizoids simply hold moss onto their perch without digging in, which means that those mosses on your tree or shrub are simply friends hanging out and not a parasite doing damage.

Additionally, bryophytes are nonvascular – a trait that contributes to their small stature. Without this internal vascular system,  which larger plants have, mosses cannot pump water or nutrients long distances. Instead water and nutrient absorption occurs throughout the surface of their body. This feature is simple yet effective due to all the surface area of their body structure. Finally, instead of producing seeds, bryophytes rely on spores, which are more vulnerable structures that rely upon wind or water for distribution. Similar to the spores produced by ferns and fungus, they do not travel long distances – a few inches at most. 

Despite their basic structures, these plants are architects! Their short stature creates habitat akin to a miniature forest providing shelter for tiny creatures. They help nurture barren surfaces by helping to create and build healthy soil while reducing erosion, thereby setting the stage for larger vascular plants to move in. Mosses contribute to the water cycle by absorbing water and slowly releasing it – like a sponge. They also have a superpower allowing them to be protected during the dry season and then quickly rehydrate when the rains return. They aid nutrient cycling by altering pH and absorbing carbon. They are pollution intolerant since they absorb directly through their thallus (body) without a filtration system and are therefore an indicator of local environmental health.

Not to mention, these modest green beauties humbly provide the wonderful green backdrop that all the other flora and wildlife enjoy. Get up close and investigate these miniature marvels!

Photo Credit Summer Swallow.

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