Mosses Explained

   Written By Jack Noro                     

So many of us already know of and use moss in our terrarium builds, animal enclosures and general horticultural endeavours however most people simply know its care requirements without actually knowing why it has such care requirements and the implications of this. As a firm believer in the idea that understanding how something functions as a whole, allows one to intimately understand its applications intuitively, I thought looking at moss like this might allow more people to understand its uses and how best to care for it. In this article we will look at how moss came about and how it differs from typical plants, the relationship it has with the environmental variables around it and then how this ties in with its care requirements.

When did moss evolve?

Starting from the beginning, the first plants would technically be green algae that came into existence over 1 billion years ago, then terrestrial plants evolved from there around 470-500 million years ago, however these were very simplistic plants, likely resembling things like pond-scum, not the plants we see today. Shortly after this evolutionary point, mosses began to evolve and divert pathways about 450 million years ago. While they are still a terrestrial plant, they are so different from the typical plant structure that they belong to an informal group called bryophytes. These are none vascular plants where most plants fall into the tracheophytes (vascular plants) category but don’t worry, we are exploring their differences next.

What makes moss different from typical plants?

So normal plants, Tracheophytes, has an ‘internal plumbing system’. Meaning they have two types of vascular tissue called Xylem, which transports water and dissolved minerals upwards from the root system throughout the plant and Phloem which distributes sugars and amino acids that are produced by photosynthesis throughout the plant. You can somewhat think of these tissues as the veins and arteries that allow our own bodies to distribute blood to all the areas of our bodies, sending oxygen and other components to needed areas. Now Bryophytes, mosses included, don’t have these vascular tissues at all, instead they simply absorb water and other needed components within the water directly through their cell walls, like a sponge. With this in mind, we can now understand why moss required humidity to thrive as well as be so sensitive to drying out and flooded out. That being said there are species of moss that evolved further to be able to reactive and awaken when dried out and subjected to water again, as well as species that evolved to live an aquatic life. It also explains why they don’t have typical roots like you would imagine for most plants. Instead, they have structures called rhizomes and its only function is to anchor the moss to whatever surface it is growing on. Now we understand how moss differs from typical plants; we can look at its relation to the environment’s variables.

Mosses Relationship with Light

                Being ground coverage, they are primed for low light conditions such as under planted canopies and forest floor debris. They don’t have a waxy cuticle, a protective layer on their leaves, nor do they have the protective lignin structures that give the “woody stems” in other plants. This means direct sunlight will dry them out very quickly. For the drawbacks they do have, they also have some pretty unique traits that help them overcome their lower light conditions. For example, they can photosynthesis in extreme temperatures from -15 all the way up to 40 Celsius. Not only that but they can also utilise the green light spectrum as a lot of the other parts of the spectrum can be filtered out by the time the light rays reach the moss. When dried out from excessive heat they can absorb water to rehydrate and begin photosynthesis again within a few hours.

Mosses Relationship with Soil pH

                It’s pretty much said everywhere that moss prefers slightly acidic soil, however rarely explained why that is the case. At first, it seems counterproductive as acidic soil actually has less nutritional content for plants because acidic often neutralise vitamins and minerals in the soil. However, if we refer back to the fact that mosses use their rhizomes to anchor themselves to the substrate and do not acquire any nutrients from a root structure like normal plants then it’s easy to see why the lower nutritional content does not matter to them. They prefer acidic soil because with this information in mind, there is typically less plant life if acidic soil, meaning they have less competition to grow against, quite important when mosses are on the slower growing side compared to a lot of other plants. Some mosses are even known to secrete their own mild organic acids that lower the local substrate pH over time.

So What Does This All Mean?

                So now we have a good understanding of mosses relationship with the variables around it, we can understand the implications of its evolution and the service it provides by existing. Traveling via spores and fragmentation, thriving in situations normal plants cannot, it is typically a percussor to plants and lays the groundwork for terraforming an area into a place where plant activity can thrive. It acts as a literal blanket that prevents soil erosion and creating a humid microclimate that begins to host beneficial insects such as the detrivores we know and love like millipedes, springtails and isopods. Which in turn brings predatorial insects and even larger animals to the area, each having their roles in the nutrient cycling process. Which in turn introduces extra carbon and nitrogen into the current substrate on its own. On top of this, the moss collects organic debris that also slowly accumulate in the soil, changing the once baron, loamy soil into a moist, nutrient-rich topsoil, further supporting the animals in the new ecosystem while also allowing juvenile plants to grow and thrive into larger ones. Once again, in turn providing supportive factors such as shade and more organic debris over time and using some of the nutrients now available in the soil to keep things in balance.