The secret world of non-vascular plants

By Karen McGregor

Mosses are critical for the entire ecosystem, reports Karen McGregor 

HAVE you ever wondered what goes on beneath your feet while walking in a rainforest? Or considered how miniature plants such as mosses impact your life? Then the IFFA Moss, Liverwort and Lichen excursion was for you! On a lovely early spring day in September, 25 people joined Mary Gibson on a walk and talk in the Rainforest Gallery, just outside Warburton. Mary Gibson has studied these plants for over 20 years and shared with us many interesting stories about their tiny world. 

First we learnt about how varied the mosses, liverworts and hornworts are. These three groups of plants are collectively known as bryophytes; bryum is the ancient Greek name for moss, and phyte meaning plant. They are probably the first plants to colonise land. They reproduce via spores. Bryophytes are non-vascular as they don’t have phloem and xylem like other plants, so can’t transport water and nutrients to great heights (hence their small stature). We did see the tallest moss in the world on the day, Dawsonia superba which can get up to 30cm tall! 

As usual, systems that try to categorise different bryophyte types are full of exceptions. Generally speaking mosses have leaves and stems, however liverworts and hornworts can also have leaves and stems. There are liverworts which have flattish leaf like structures called a thallus. The thallus is tissue made up 

of undifferentiated cells, unlike the complex cell structure of a leaf. You will never however find a thallose moss. Bryophytes have rhizoids instead of roots, and can take in water through any part of their body. This makes them great bio-indicators as they show the effects of pollutants very quickly. They are also desiccation tolerant, able to dry out and refresh again with the addition of water. 

Some invertebrates will only associate with particular bryophytes. Mayflies cut the cells in mosses and eat the nutrients. They also vertically cut cells and use them as a casing as bryophytes provide a cool and moist microhabitat. Some birds choose particular mosses for their nests to attract or repel specific invertebrates. They will attract insects that are food sources or that will assist in keeping nests clean. Birds also use mosses as camouflage. 

Bryophytes act as a soil stabilizer, for example Funaria hygrometrica and Ceratodon purpureus, which are known as fire mosses, have mycorrhiza in their leaves which assist in germination of native plants. After a bushfire these mosses are vital in covering the soil, holding nutrients in their bodies and not allowing nutrients to be washed away. 

Bryophytes are critical in the hydrological cycle. In cloud forests and rainforest mists, bryophytes take the moisture in the atmosphere through their bodies. When they are saturated they release the water which trickles down to the roots of other plants. 

FURTHER READING 

Meagher and Fuhrer (2003) A field guide to the mosses and allied plants of southern Australia or Read and Slattery (2014) Mosses of dry forests in south eastern Australia.