Leaves Of Grass

Forest and Bird, Issue 308, 1 May 2003, Page 38

Leaves

Of Grass

ANN GRAEME

explores the nature of grasslands.

o the casual glance, grasses look like the poor cousins of the flowering plants. Their flowers aren’t colourful or fragrant, they aren't tall and grand like trees, and they just don’t have the variety of form that herbs, climbers and shrubs have. Most grasses are — just grassy. Yet to mankind, grasses are the most important plants on Earth. Our earliest ancestors came down from the trees to the grasslands which were displacing the forests in the dry times of the Miocene. They adapted to walking upright and running on the open savannah, unlike the other primates which stayed swinging from the trees. Much, much later, when human societies arose, it is no exaggeration to say that we could not have advanced far beyond being ‘hunters and gatherers’ without the grasses. Of the modern world’s twelve leading crops, five are grasses — wheat, corn, rice, barley and sorghum — and grass grains provide more than half of all the calories that people eat. Sugar cane is a grass and so too is the versatile bamboo. New Zealand’s farming depends on introduced pasture grasses. Grasses are peculiarly suited for grazing animals because the narrow grass blade keeps on growing from the base, despite being nibbled off. This may seem blindingly obvious as you toil behind the lawn mower, but no other leaves would keep growing —

and growing — and growing — despite being cut off. It is this capacity — to keep replacing the damaged leaf blade from the leaf sheaf and to protect the growing leaf bases at ground level — that feeds our cattle and sheep and has allowed grasses to dominate about a fifth of the world’s vegetation. It is no oversight of nature that grass flowers are inconspicuous. Across the rippling grasslands runs the wind, their pollen carrier, which needs no perfume or colour to summon it. Instead the grass

flower hangs out its stamens, laden with pollen as small and light as dust, and the wind does the rest. The pollen-receiving stigma is held erect like a feather duster, to catch the blowing pollen grains. Grasses grow from the seashore to the mountain tops and from the tropics to the polar regions. They are rare, though, in rainforests including our native forests, probably because the forests are still and dim; unsuited to the sun- and wind-loving grasses. In New Zealand, grasses are the second largest family of native plants (following daisies). There are 188 native grass species, as well as 272 introduced and naturalized species. The familiar drooping heads of native toetoe line our waterways and the unwelcome flags of Argentinean pampas crowd our roadsides. On the sand dunes the silver spinifex binds the sand and its spiky seed heads roll along the beach. But it is in the high country that native grasses come into their own. Tussock grasslands rule the South Island high country and much of the central North Island. A sea of waving grasses, the ripples over the landscape, outlining the bones of the land. In turn, the tussocks create a world which shelters smaller grasses, gentians, orchids and many other herbs, and support a myriad of insects and birds. Tussock grasses belong to three groups;

the tall snow tussocks (Chionochloa) and the short tussocks (Festuca and Poa). They grow in tightly bunched tufts, their long, narrow leaves emerging from sheaths. Each tussock leaf is a gutter, and will catch and funnel water, even from fog so fine it will scarcely wet the ground. Research by Professor Alan Mark, a member of Forest and Bird’s executive, has shown the importance of the tussock grasses to the upland water catchments which feed the South Island’s hydro, irrigation and domestic water schemes. Although the tussock leaves go brown in winter dormancy, they are not dead, and will function and photosynthesize for several years. Tussocks are adapted to withstand frost, snow, wind and even the occasional natural fire. Our native snow tussocks grow slowly. Each plant can live to a great age, perhaps as long as our oldest trees. Snow tussocks have been described as ‘perhaps immortal’. In their longevity and permanence, these tussock grasslands are akin to forests, rather than to our ephemeral lawns of introduced species. Few seedlings need survive in such a longlived community, so many tussocks do not flower every year in the wild (though they may do in your garden). Instead, flowering every three or four years (in response to warm summers a year earlier) provides

ample seeds to perpetuate the species. In other parts of the world native mammals graze the prairies and savannahs but our native tussock lands have evolved ungrazed, except by birds such as moa and takahe, and the chewing mandibles of insects. In prehistoric times, the New Zealand grasslands never felt the nibble of

sheep and rabbit teeth or the wrenching tongues and trampling hooves of cattle and deer. New Zealand tussocks are not adapted to these grazing mammals, nor to constant burning which wastes the meagre nutrients of the mountain soils. As a result of nearly two centuries of grazing and burning, the tussock grasslands have degraded to but a shadow of their former glory. Like so many native New Zealand species, tussocks are large, slow-growing, and vulnerable. They are a native community special and dear to New Zealanders and they need and deserve protection just as much as do our tall forests and alpine herb fields. Recognition of tussock lands is coming at last. The Torlesse Conservation Park in North Canterbury was the first park designed to encompass tussock lands, and a second park called Te Papanui has just been created in central Otago. The Prime Minister, Helen Clark, an avid back-country tramper, lends her support to tussockland protection. Through the current review of pastoral-lease tenures (see Forest & Bird, August 2002), further opportunities should become available to protect yet more of our tawny tussock heritage. — ANNE GRAEME is the national co-ordinator of Forest and Bird’s Kiwi Conservation Clubs.