Moss & Lichen

Skyrail Nature Diary: April 2010

This month we explore the small, often missed world of moss and lichen. These two rainforest residents grow on the surfaces of larger hosts, be it trees, shrubs and even rocks.

They create beautiful, lush carpets and interesting shapes, colours and textures. They are found everywhere in the rainforest, you just need to stop and look.

The unassuming moss, which creates a velvety carpet along fallen rainforest tree trunks and rocks, probably created the world's first forests. Although, at just 5cm tall, these forests would have been difficult to visit!

Moss represents an evolutionary step up from algae; it is considered one of the simplest organisms to be included in the Plant Kingdom. Mosses are classified as bryophytes, which are non-vascular land plants. This means they are plants that live on land, but do not have vascular tissue to circulate liquid. They produce spores, rather than seeds and do not flower. Hornworts and liverworts are also bryophytes.

Bryophytes live in moist environments, making our Wet Tropics Rainforests the perfect place to find them. Mosses are usually only a few cells thick in structure, despite this, when you look closely at them, they look like tiny, individual plants. Mosses tend to cluster together and create lush, carpets of growth.

Lichen are another unassuming rainforest resident, which can be found growing on trees, trunks, branches, rocks and even individual leaves. Formerly classified as individual plants, lichen are in fact the result of a successful, inter-dependent relationship between fungus and algae.

The fungus component of lichen absorbs water and minerals, while alga uses chlorophyll for photosynthesis, to manufacture food. Fungal threads create the 'body' of the lichen and the algal cells live within them. The threads give the lichen strength and prevent the alga from drying out.

Lichens are a robust life form that can be found anywhere on earth with sunlight and clean air. In the Wet Tropics there are three main types of lichen, crustose, foliose and fruticose.

Crustose lichens are the lichen you see growing flat against trunks and branches. They form, flat, crusty plates that grow slowly outwards, increasing their radius by as little as 0.5mm a year. Foliose lichens often grow near mosses and are leafy in appearance. Finally, fruticose lichens are even more finely branched and can become quite large; these are the lichens that hang like 'beards' from branches.

Traditionally, lichens were used in many countries to make dyes. The dye litmus is derived from lichens: it becomes red when exposed to acid and blue when exposed to an alkali.