Masses of Mosses

Forest and Bird, Issue 297, 1 August 2000, Page 30

Masses of Mosses

has a particular

enthusiasm for mosses.

—JO MACKAY

4 wealth Of mosses enhances the character of wild New Zealand Jo MACKAY has developed a special interest in them

ompared with other temperate regions, New Zealand is exceptionally rich in mosses. ‘The lush appearance of our forests is due largely to the small plants which find a niche on trunks and twigs, on rotting logs and on the forest floor, wrote scientist Jessica Beever in The Mosses of New Zealand. She says New Zealand mosses are so diverse and luxuriant that foreign moss experts ‘go gaga’ when they visit. New Zealand has (at last count) 523 species of moss and 23 further varieties. (See box, ‘A Great Variety’) These mosses grow from the sea shore to the alpine zone; from moist, temperate western areas to places ruled by semi-arid eastern climates. They may grow 30 metres deep in lakes and streams, or on exposed rocks, on rotting wood, and even on animal carcasses. Some grow in thermal regions on soils hotter than 50 degrees Celsius, and some in very dry environments. Their cells can dry out completely and come to life again when re-wetted. Landcare scientist Allan Fife — one of New Zealand’s few full-time moss scientists — writes that bryophytes (including the mosses) offer important clues to the history and geography of all plant communities. They are ancient plants, which seem to evolve slowly, and be able to persist within specialised habitats without changing. Some species are very particular about

where they'll grow. For example, Jessica Beever has found that a very different mixture of moss species grows on the black tree fern (mamaku) compared with the ponga tree fern, and nikau palms, in the same forest. Some mosses have important ecosystem roles. In forests, mosses hold groundwater and release it slowly, stopping erosion and nutrient run-off. They also provide homes for invertebrates.

identifying Mosses

ow do you tell mosses apart? Here’s the bad news: if you've only got a handglass, often you can’t. To identify most mosses to their species, you need to look under a microscope. The good news is that you can learn to distinguish the most common moss families by sight, and if you want to learn more, Jessica Beever’s moss book is very helpful. Then, if you get really keen, you can come along to an annual bryophyte workshop, and ‘hang out’ with the rest of us! Pve found from personal experience that by far the easiest way of identifying a moss is to point a moss expert at a microscope and look interested. There’s so little known about most mosses, including their geographical spread, their growth rates or where they fit in their habitat, that even beginners learning about mosses can make worthwhile

contributions to scientific knowledge. Identification of mosses is determined by the shape of the tiny leaves, how far the central nerve of the leaf extends, and the cell structure. Sporophyte design and colour are also key identifying features. The first step, however, is to sort out mosses from liverworts, hornworts and lichens. Lichens are different altogether; they are a combination of algae and fungus, often coloured brilliantly, and looking almost as if made of plastic. Leafy liverworts and mosses can be very similar, however — they both belong to a group of plants called bryophytes (see box, ‘Two Plants in One’) — but there are a number of striking differences. The easiest way is to look for stalks and capsules (sporophytes). If you find some, your subject is probably a moss. Moss sporophytes have a wiry stalk, coloured red, brown or black, which lasts for some time. The stalks of liverwort sporophytes are translucent and flimsy, and last only a day or so. Liverwort spore capsules split open into quarters to fling out the spores. Moss capsules start off green, usually ripen to yellow or red or brown and disperse their spores through a round hole at one end, which is ringed with tiny ‘teeth. This can all be seen with the naked eye — look for sporophytes next time you see a patch of moss, and take a close look at the capsule. Moss and liverwort leaves also differ: liverwort leaves are often deeply lobed, never have central veins, and tend to sit fairly flat in two rows, with a third row of leaves on the underside. Moss leaves aren’t lobed and most do have nerves. Their leaves can be flattened, in swirls, or rows.

A Great Variety

ew Zealand has (at last Ni count) 523 species of moss and 23 further varieties, in 208 genera. Only 20 percent of our moss species are unique to New Zealand, however. We share many moss species with South America, Australia and smaller islands in the South Pacific. This compares with other plant groups which contain many species found only in New Zealand — about 80-85 percent of our flowering species and 45 percent of ferns are found here and nowhere else. It is not known how many mosses may have been introduced.

Two Plants in One

le moss life cycle is fascinating — it alternates between two totally different generations of plant. The leafy green thing we call a moss is one generation. The stalks with capsules that grow from the leafy plant is the second generation — but also a different plant. The leafy generation (gametophyte) has only half the chromosomes of the stalk and capsule (sporophyte). The leafy plant has male and female parts that reproduce sexually to produce the sporophyte, which simply releases spores that grow again into the leafy generation. The leafy generation can also reproduce asexually, often producing special ‘bodies’ that break away to grow into a new plant. This two-plant life cycle is shared with liverworts and hornworts which make up a group of plants called bryophytes.

New Zealand has about 580 species of liverworts, which together with mosses make up more than 1100 species of bryophytes. This number of bryophytes compares significantly with the roll call of about 2500 species of vascular plants.

There are three broad classes of mosses:

THE SPHAGNUM MOSSES

There are about nine similar species of sphagnum in New Zealand. Sphagnum grows in extensive spongy masses in boggy places. They have large dead, porous leaf cells that can enable the plant to hold about 20 times its own weight of water. This capacity is used by the $10 millionplus sphagnum export industry, which collects the moss from its natural swampy habitat to export to Japan for potting orchids in nurseries.

ROCK, OR LANTERN MOSSES

The Andreaea mosses are another small distinct group. These dense, dark mosses grow on wet or dry bare rock, sometimes in exposed, inhospitable alpine areas. Under a microscope, they are a rich dark red or brown, with stiff, pointy leaves — a miniature version of a tough alpine plant. Tucked between the leaves are the sporophytes on short, stout stalks, with round capsules. Unusually for a moss, the capsules split into four to release the spores, but remain attached at the top, looking like a lantern.

THE REST

All the other 57 families of mosses resident in New Zealand are in the Bryales class, which covers a huge diversity. New Zealand has the largest moss in the world, the striking Dawsonia superba, which looks like a 25 centimetre-high pine seedling. Its large velvety brown capsules with fluffy white teeth gives it away as a moss (see below).

Most forest walkers will spot the Dicranoloma species — bright green or yellow-green mosses which grow profusely in fluffy carpets, and the common Ptychomnion aciculare which I like to call ‘pipecleaner’ moss. It has scruffy, glossy, pale green leaves and often a red stem, growing upright, again in tufts. One friend bashfully admitted to me that the Ptychomnion makes great bushman’s toilet paper.

Conservation efforts

ome New Zealand mosses may be under threat from harvest. Many are believed to grow very slowly. Sphagnum moss harvesters on the lush West Coast, where growing conditions are best for the species, tend to leave a boggy area at least three years before coming back for more. Recently, species other than sphagnum have been sighted in flower shops. Moss expert Jessica Beever warns that moss used in flower decorations has probably been taken from a natural area, rather than cultivated. There’s a danger in this, she says: taking any element from a natural ecosystem can result in imbalances and loss of habitat or food for other creatures. Some 60 New Zealand mosses are already considered by the Department of Conservation as ‘threatened’ or ‘believed threatened’. The biggest conservation problem for mosses (and other small plants and animals) is the comparatively small amount of attention they receive. When we take a close look and realise the extent of the stunning biodiversity within these tiny worlds, it begs the question: are we really committed to protecting all of New Zealand’s biodiversity? Our research and conservation funding focuses on larger animals and plants that we can see easily. Yet 99 percent of plants and animals are smaller than one centimetre and their contribution to ecosystem functions is huge. What changes are going on with these tiny creatures that we

haven't noticed, and how will that affect the whole ecosystem? Humans the world over are charmed by ‘charismatic mega-fauna’ sometimes to the neglect of the biodiversity of the whole ecosystem. This rampant size bias may come back to bite us, if important but neglected small species become extinct, and irreplaceable parts of ecosystems are

lost.

Dr Jessica Beever, Moss Enthusiast

lant physiologist Jessica Beever up in the Waitakere Ranges of Auckland one day, with one of the best moss identification books then available, Allison and Child’s The Mosses of New Zealand. She tried to ‘key out’ a moss with her grandmother’s microscope, by chance picked a distinctive one, and found it a ‘piece of cake!’ Two decades later, Jessica’s enthusiasm for her little green fuzzy friends continues. As a Landcare associate in Auckland, she studies and describes mosses. She revised Allison and Child’s book, creating the ideal moss-lovers’ companion, with fullcolour photos and quick clues to identification. By playing sleuth, Jessica has also helped to protect one of New Zealand’s rare aquatic mosses, known from only two locations. A herbarium specimen of Fissidens berteroi had been collected from the Onehunga Springs a century before. This freshwater spring, now in the depths of urban Auckland, had almost disappeared beneath a pumping station many years ago. Jessica tracked down the one small outlet where the spring saw the light of day. There, she found the moss — it had been hanging on to life on a patch of wet concrete for decades. Steps are now being taken to pro- tect the site.