Lichen in our landscape
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| Haematomma
alpinum is an eye-catching epiphyte of Melicytus alpinus in subalpine
grassland. Image - Barrie Willis. Click to enlarge. |
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| Pseudocyphellaria
maculata is an effective nitrogen-fixing species in subalpine grasslands,
and one of the many New Zealand lichens that has an importance as
a biological fertiliser. Image - Barrie Willis. Click to enlarge. |
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| Xanthoria
elegans is a conspicuous high-alpine, bipolar lichen, occurring at
high latitudes and high altitudes in both Northern and Southern hemispheres. Image - Barrie Willis. Click to enlarge. |
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| Rhizocarpon
geographicum forms vivid map-like patches on rocks from sea level
to high-alpine sites. The yellow-green pigment that it contains is
an effective sun screen. This lichen is commonly used to date moraine
surfaces. Image - Barrie Willis. Click to enlarge. |
Lichens are common components of all landscapes in New Zealand, from inner city footpaths to the summit rocks of Aoraki Mt Cook at 3650 m, even sometimes submerged on rocks in streams and on rocky shores, and with footholds in a myriad of microhabitats in between these extremes. In many landscapes lichens are dominant biological components, clothing exposed rock surfaces, tree bark and canopy branches, and even man-made structures (for example worked wood, tar seal, glass, plastic, concrete and iron) – so much so that often covering lichens are seen before the landscape’s underlying rock, as in the schist tors of Central Otago, or on moraine or riverbed rocks near glaciers. Many natural (and man-made) surfaces are given colour, texture and interest by a mosaic cover of lichens.
Lichens are in fact fungi that have evolved a specialised mode of nutrition: symbiosis with a photosynthetic partner – either a green microalga or a cyanobacterium or sometimes both together. This highly successful strategy for nutrition, transferring carbon from the photosynthetic ‘producer’ to the fungal ‘user’, allows lichen associations to become ‘plantlike’, and thereby to exploit a much wider range of terrestrial habitats than would otherwise be available to fungi alone. Lichens are the ‘farmers’ of the fungal kingdom. While their non-symbiotic relatives continue as hunter-gatherers of transient carbon sources, the lichen fungi have become indoor gardeners, cultivating and perpetuating their internalised source of food. This agrarian control over food resources confers both stability and the potential to occupy entirely new ecological niches. In human development, agriculture permitted the rise of populous, sedentary, highly complex civilisations. For the fungi, ‘algaculture’ has led to the development of structurally elaborate, self-sufficient, long-lived thalli that we call lichens. The nutritionally autonomous lichen colonises inorganic or indigestible substrata and often occurs in extreme microhabitats with little to offer the hunter-gatherer of ephemeral food resources. The success of the lichen symbiosis, which has evolved independently in a number of different lineages, is such that nearly one-fifth of all known fungi are lichen-forming. Recent molecular studies have shown that the lichen-forming fungi are much older than was previously thought and that many lines of free-living fungi are derived from lichen-like ancestors.
Although they are tolerant of a wide range of ecological conditions, lichens are extremely sensitive to atmospheric and terrestrial pollution. The delicate nutritional balance between photosynthetic and fungal partners in the lichen symbiosis is very easily uncoupled by a range of pollutants, and consequently lichens have important uses as biomonitors of environmental health and as bioindicators of environmental change. Lichens also produce a wide range of bioactive compounds, including ingenious photoprotective chemicals that act as sophisticated sunscreens, blocking the harmful effects of UVB, and allowing lichens to survive readily in high-light habitats. These photoprotectants can be monitored to give useful information on changes in UVB levels.
Ecologically, lichens are also important as major nitrogen-fixers in grassland and forest ecosystems. New Zealand lichens, especially those that have the capacity of fixing nitrogen, grow a good deal more quickly than is generally imagined, making them important as ‘biological fertilisers’, some producing 2–4 cm linear or radial growth per year in a short burst of winter growth. In this role lichens are important in colonising disturbed habitats – perhaps investigation into possible practical applications of lichens in habitat restoration could be useful.
Lichen communities are therefore vital primary producers in the cycling of carbon and nitrogen nutrients in our forest and grassland ecosystems, and in addition they can tell us a great deal about the health of our environment.
However, before we can really appreciate the value of lichens in our landscape we need to know what lichens we actually have – and what to call them. An internationally recognised sourcebook of information with keys, descriptions, distributions, chemistry and ecology is therefore a basic necessity. Such a work is a Flora (although for lichens, which are fungi and not plants, the correct term is a lichen Mycobiota). The first modern account of New Zealand’s lichens was written between 1973 and 1983, largely from the confines of the Natural History Museum in London, where the author was based. It was published in 1985 as part of the Flora of New Zealand series, and dealt with 996 taxa in 210 genera.
Since then, however, knowledge of our New Zealand lichens has increased dramatically. The rate of disovery of lichens new to New Zealand, and the accelerating pace of lichen systematics with consequent name changes, made a revision of the Lichen Flora necessary. Work on a revised edition is now complete and publication is planned for 2005. Based in New Zealand this time, the author has been able to see lichen communities at first hand when systematic problems were encountered. He was also able to use lichen herbaria worldwide, including those in New Zealand (Manaaki Whenua has guardianship of one of New Zealand’s lichen collections in the Allan Herbarium at Lincoln).
Since 1985 the list of New Zealand lichens has grown by nearly 70% (both in species and genus numbers) with Flora of New Zealand Lichens (2nd edition) discussing 1680 taxa in 350 genera. This represents about 10% of the world’s known lichens, with the lichens in our regions including endemic, Australasian, austral, pantropical, paleotropical, circum-Pacific, cosmopolitan, southern xeric and bipolar elements. Lichens should surely be key components of any biogeographical debate. With lichens now emerging as biomonitors of choice in studies of atmospheric and terrestrial pollution and of global environmental change, and considering their importance in nutrient cycling in forests and grasslands and their potential value in habitat restoration studies, the publication of a new edition of Flora of New Zealand Lichens will be an essential resource. It may even become clear just how important lichens really are in our New Zealand landscape!
Further Reading
Malcolm, W.M.; Malcolm, N. 2000: New Zealand Lichens. Micro-Optics Press, Nelson. 134 pp.
Purvis, W. 2000: Lichens. The Natural History Museum, London. 112 pp.
Malcolm, W.M.; Galloway, D.J. 1997: New Zealand Lichens. Checklist, Key, and Glossary. Museum of New Zealand Te Papa Tongarewa, Wellington. 192 pp.
Galloway, D.J. (Forthcoming) Flora of New Zealand
Lichens, Ed. 2. Manaaki
Whenua Press, Lincoln.
This publication will be available from Manaaki
Whenua Press www.mwpress.co.nz.
Primary Contact:
 | David Galloway Email  |
Landcare Research | |
Phone: 03 470 7200 |