Mosses
 

Not just decoration

Mosses are a very important component of coastal forest ecosystems. They cushion the soil against rain and runoff, thus helping to prevent erosion. They intercept nutrients dripping from the canopy of the trees, and temporarily store those nutrients. As moss tissues gradually decay their constituents are incorporated into  fungi and eventually delivered to the roots of nearby trees. They also provide shelter for organisms such as mites, springtails, and small worms -  the food supply for other creatures higher up the food chain. Mosses also produce a protective covering that moderates environmental extremes, thus nurturing a thriving community of micro-organisms, which is very important for ecosystem health.

 

PSPS would like to thank Terry Taylor, BA BLS,

for contributing this page, March 2007

Pacific Spirit Park is endowed with a beautiful covering of mosses. Although most visitors are not consciously aware of this mossy raiment they are probably unconsciously aware of it. For it is the mosses that give the woods that subtle green hue that is so elusive, yet pervasive. It is that subtle green that helps to make the park such a pleasant place.

You may have noticed that most mosses are not single, isolated plants, but grow in dense colonies. They are usually very social organisms. It is not just an accident that they are so social. They need to cooperate in order to survive. These small plants do not have roots, but absorb water and minerals directly through their leaves and stems. By growing close together they can share the water that seeps across them. This close proximity also protects the mosses from extremes of temperature and drought. There is strength in numbers..

Look again!

Not all the mosses you see on your walks are the same. There are a number of different species in the park, and they have different preferences as to where they live. Those on the ground are different from those on tree trunks, which are again different from those on rotten stumps.


The most common species on the forest floor is the Oregon beaked moss (Kindbergia oregana). This pale green plant is shaped like a tiny feather with many densely packed, short side branches, and the shoots form thick mats over the forest floor.

Whole ecosystems

If you look at the trunk of a tree you will see that it has a whole ecosystem growing on it. On the part of the trunk that receives the most moisture, and at the base where there is greater humidity mosses form continuous colonies. These dense colonies can also be seen on the lower parts of salmonberry stems. Close to the ground there is a layer of still, moist air. Above this layer, where it is drier, the stems are bare. On the drier parts of tree trunks mosses are replaced by lichens. There is a rain-receiving side of the tree, and a rainshadow side of the tree.

Deciduous trees are more favorable for mosses than conifers since their bark is more nutrient-rich and less acidic. The bigleaf maple is the best example of that. An old maple trunk in a shady site is covered by moss. There is more moss and more moss species on this maple than on any other kind of tree in the park. The most common one is the Yellow Moss (Homalothecium fulgescens). It forms a thick carpet on the lower parts of the trunk. Its long stems are a shiny yellow-green, hence the common name.


Mosses and liverworts are important and delightful inhabitants of Pacific Spirit Park. They are especially diverse and luxurious because of our rainy climate, and a close look at their intricate details can make a walk in the woods all that more enjoyable.

Spores not seeds

Other structures you can see on mosses if you look closely are the spore cases. These small plants do not produce seeds, but reproduce from tiny, seed-like bodies called spores. Each spore is only a single cell. Spore cases are usually produced in spring, but old cases can remain right through the year. For the botanist they are important features for species identification. They are tiny brown cylindrical bodies on long stems that project above the moss itself, and different mosses have different shaped cases. The top of the case is covered by teeth that control the rate at which the spores are released. These are not visible without optical aid, but can be seen with a magnifying glass. Such a magnifier can reveal many of nature’ s secrets which are otherwise hidden from us.

Another special habitat is the park’s rotten stumps. For most of the year these are full of moisture, and they support their own unique moss-type community that is not found on the ground or on tree trunks. This is a liverwort community. Liverworts look essentially like mosses, but are actually a separate group of plants. They usually require more moist micro-sites than most mosses, and old stumps are just ideal for one of them – the Little Hands Liverwort (Lepidozia reptans). Little Hands Liverwort is a minute plant that forms a thin green coating over very rotten coniferous wood.


The majority of the green coatings on stumps are colonies of this liverwort. It possesses tiny branches that diverge from the main stem at right angles. The leaves are almost invisible to the naked eye, but with a microscope they have three finger-like lobes, hence the common name.

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Leucolepsis acanthoneruon

Plagiomnium venustum

Plagiothecium undulatum

Kindbergia oregana

Plagiomnium venustum and others

Lepidozia reptans

Isothecium myosuroides

Polytrichum juniperinum