Bryophytes in Irish Habitats
Walking through the woods, forests and even cities in Ireland you will have, at some point, observed Bryophytes scattered throughout the landscape. So, what exactly are they and what habitats to find them in?
What are Bryophtes?
Bryophytes are an informal group of small plants containing three distinct lineages, the mosses, liverworts, and hornworts. We often overlook these diverse and adaptable plants and describe them as “simple” because they do not possess a means of transporting nutrients internally (vascular system), they do not have true roots, they reproduce with spores and they do not produce seeds and flowers such as the ferns and flowering land plants we are all familiar with. However, bryophytes are quite remarkable and show exceptional resilience. In fact, some species are tolerant to extended freezing and dry periods and when moisture returns, they rapidly resume photosynthesis and growth!
These incredibly diverse plants grow in many regions and habitats across the planet, with 25,000+ species having been recorded to date. That is because all they need is adequate sunlight, humidity, and a stable, moist place to attach and grow. Typically, they thrive in areas such as tree trunks, bare rocks, soil and even the cracks in the brick walls of your house. Of course, there are rebellious bryophyte species, which like to bend the rules and grow in regions where they do not usually grow, such as the liverwort Carrpos which grows on salt pans and the Cornish Path-moss (Ditrichum cornubicum), which grows on the copper-rich soil at Mountain Mine, Allihies, here in Cork. Notably, Allihies is one of three sites globally where Cornish Path-moss is known to inhabit and this rare species is listed as Critically Endangered on the Irish, European and Global Red Lists and is also protected by Irish legislation through the Flora (Protection) Order 2015.
Bryophytes thrive in damp conditions such as tree trunks and bare rocks by a flowing river. Their presence supports tiny invertebrates and insects, contributing massively to the biodiversity in a region. Bryophytes thrive in Ireland’s climate and over 50% of the European bryophyte flora are represented in the 797 bryophyte species here. This means we have a pivotal role to play in protecting rare and endangered species and their habitats. For instance, the blanket bogs and raised bogs in Ireland are some of the planets’ oldest living, near-natural ecosystems. This has led to many bogs being designated as protected areas, Special Areas of Conservation (SACs) under the Habitats Directive and Natural Heritage Areas (NHAs) in 2004 under the Wildlife Amendment Act (2000).
These ecosystems rely on the continual growth and productivity of the bryophytes from the Spaghnum genus. There are over 20 species known to grow in the bogs, some growing up to a meter high while others are found in hollows and pools. It is one of the most important plant species of the bog as they retain mass amounts of water and form a critical carbon sink. Did you know that Spaghnum mosses are so good at absorption that during WW1, they were extensively harvested in Ireland to use as wound dressings!
Swan’s Neck Thyme Moss
Mosses such as the common Swan’s neck Thyme moss (Mnium hornum) grow extensively throughout the country and are vital in supporting ecosystems. Tiny invertebrates, fungi and other plants rely on their presence for food (feeding or hunting other insects). Red squirrels have even been observed using moss to line their dreys. In the past, Swan’s neck Thyme moss was used to stuff mattresses as they it was thought it would help you sleep better! Interestingly, it was discovered that the moss contains the fatty acids arachidonic acid, known to contribute to improved immunity and inflammatory responses; so perhaps it did pose some benefits after all. However, we definitely don’t recommend harvesting it yourself in search of a good night’s sleep!
Common Liverwort Moss
Like the Swan’s neck Thyme moss, the common liverwort or umbrella liverwort (Marchantia polymorpha) had an alternative use. During the Middle Ages in Europe, the common liverwort was thought to treat diseases of the liver. This was down to the shapes of the leaves which resemble those of the fatty lobes of our livers, and it was common practice at the time that a plant resembling a human organ was thought to be useful in treating that organ. Today however the common liverwort is renowned for its unique aesthetic and are sold in garden centres around the country. If you are on the lookout, you might be able to spot them thriving on damp soil in your garden or in your glasshouse! A group of these plants together is truly a fascinating sight. They almost look like a group of tiny little palm trees. Perhaps they are a hideout for our local fairy population!
Naturally, they get their name from the drooping leaves which give an umbrella type effect. Although sometimes these can stand upright and resemble a starfish! The spores of this plant are incredibly hardy and have an extremely tough coat containing a substance called sporopollenin. This protects the contents of the spore, enabling it to survive for millions of years in rock sediments. In fact, the analysis of 470-million-year-old shale has revealed spores of the same age wherein the structure of the spore wall looks like concentric rings of a cut onion. Today, liverworts are the only living plants with onion-like layers in their spore walls! This means that the earliest land plants known to us, were probably related to the common liverwort we see in our gardens today.
Some lesser-known bryophytes in Ireland are the hornworts, and only three species have been recorded on the island to date. These are the Smooth Hornwort, Dotted Hornwort and the Field Hornwort (Phaeoceros laevis, Anthoceros punctatus and Anthoceros agrestis respectively). These fascinating plants have acquired their name because of their form, notably the slender, horn-shaped capsules protruding from the base of the plant. These ‘horns’ contain the spore needed to germinate. Of the three species known in Ireland, the Field hornworts are the most elusive and are listed as Vulnerable in the Irish Red Data Book. They can be found on disturbed, damp habitats such as arable fields, ditches, and hedge banks. Contrary to what one might think, the greatest threat to this species is habitat destruction in the form of afforestation and changing agricultural practices such as the cessation of tillage which provide the plant with bare, frequently agitated and water retentive soil.
Bryophytes Role in Nature
Due to their resilient nature and their ability to colonise even the barest rock face, bryophytes play a central role in the establishment of plant communities. Their life cycles and waste matter eventually form soil for other plants to germinate upon and invertebrates to thrive. They support these various lifeforms through the recycling of nutrients and alteration of the environment around them. They have benefitted humans for generations and are still doing so by becoming indicators of nutrient status and productivity of our woodlands. Evidently these magnificent plants are not so ‘simple’ after all. If you happen to spot any bryophyte species, please remember to submit your observations to the National Biodiversity Centre.
Written by Natalie Cunningham
Anthoceros agrestis field hornwort :: Northern Ireland’s Priority Species :: (habitas.org.uk)
Smooth Hornwort (Phaeoceros laevis) – Detail – Biodiversity Maps (biodiversityireland.ie)
Field Hornwort (Anthoceros agrestis) – Detail – Biodiversity Maps (biodiversityireland.ie)
Dotted Hornwort (Anthoceros punctatus) – Detail – Biodiversity Maps (biodiversityireland.ie)
Common Liverwort (Marchantia polymorpha) – Detail – Biodiversity Maps (biodiversityireland.ie)
Raised Bogs in Ireland FactsheetIrish Peatland Conservation Council (ipcc.ie)
Oxford University Plants 400: Marchantia polymorpha
Conservation and Monitoring of Rare and Threatened Bryophyte Species in Ireland | National Botanic Gardens of Ireland | The Office of Public Works
Flora and Fauna around the Bogs of Ireland (irishbogrestorationproject.ie)
What is a raised bog? – The Living Bog (raisedbogs.ie)
Swan’s Neck Thyme Moss (Mnium hornum) – Woodland Trust
(PDF) Marchantia polymorpha: Taxonomy, Phylogeny and Morphology of a Model System (researchgate.net)
Bryophytes | Basic Biology
What Is the Ecological Importance of Bryophytes? (reference.com)