Ecology - Habitats
Urban lichens in Canberra
Many lichen species can be found in urban areas and such areas provide a great variety of MICROHABITATS. Lichens in urban areas face some of the same challenges encountered by lichens in wilderness areas, but also ones that are quite different – gases and particulates from automobile exhausts, industrial pollutants, garden fertilizers, herbicides, soil compaction caused by vehicles parking or driving on unpaved areas and soil disturbances (for reasons such as construction work or cable laying). This list of urban challenges is by no means exhaustive. No two of the world's urban centres are the same. They vary greatly in features such as size, population density, pollution and climate. Not surprisingly there is variation in the world's urban lichens, though some species are found in many urban areas. It would be pointless to try to give some sort of summary of all the world's urban lichens so on this page I'll mention some of the urban lichens found in the city of Canberra, where I live. The examples on this page don't constitute an exhaustive list of Canberra's urban lichens but have been chosen simply to introduce you to a variety of urban species as well as some of their habitats. Within Canberra there are some areas of remnant native bushland preserved as nature reserves and these provide a variety of habitats not found elsewhere in the city. The Australian National Botanic Gardens are located in Canberra and have a great variety of plants not otherwise found in Canberra. However, all the Canberra lichens mentioned on this page can be found in areas outside the nature reserves and the botanic gardens.
Canberra has a population of about 325,000 people. The city has no heavy industry and is somewhat decentralised, there being several 'town centres' rather than one large central business district, with each town centre containing shopping centres and office blocks. Given these facts each town centre experiences vehicular traffic throughout at least the daylight hours as people go to or from shops or offices. The oldest of the town centres is known as Civic and was officially opened in December 1927. Some decades later additional town centres were developed north and south of Civic. For the most part the city has an elevation of between about 500 and 600 metres, though within the city boundaries there are non-urbanised hilltops with summits a little over 800 metres above sea level. Canberra is about 120 kilometres inland and has a dry, continental climate with warm to hot summers and cool winters. The mean daily maximum temperature in January is 27.7°C and in July it is 11.2°C. The mean daily minimum temperatures are 13°C (January) and -0.2°C (July). The extreme recorded temperatures have been 42.2°C on 1st February 1968 (followed closely by 41.4°C on the previous day) and −10.0°C on 11th July 1971. The average annual rainfall is 629 mm, with an average of 108 rain days per year. Rainfall is spread reasonably evenly through the year, with October the wettest month (65.3 mm) and June the driest (39.6 mm). Canberra's inland location gives the city a fairly low relative humidity. This climate information has been taken from the Canberra page of the Bureau of Meteorology website and you can find more details there.
Here is part of an area alongside Belconnen Way, a major commuter road during the morning and afternoon peak traffic periods. In the dappled light you can see what look like pale grey splashes. From a distance it would be easy to think that someone has emptied a paint can here or that you're looking at some dried cement. If you move closer and stand directly over the area you can see this and while you can now rule out paint you might still think it's some dried cement mixture. However, once you are down on your hands and knees you see this , the grey thallus and black apothecia of the crustose lichen Diploschistes thunbergianus. Few people walk in the area where that Diploschistes was growing and it is also far enough away from the road to be clear of any cars that might need to pull off the road. As you can see from the leaf litter there are some nearby eucalypt trees that also help keep bicycles away so the area was well-protected from trampling. In the first of these three photos the Diploschistes colonies are spread over an area of more than two square metres, with some thalli a handspan or more in area and, given the absence of disruption, numerous Diploschistes colonies developed in this location. Diploschistes is a fairly common on soil in Canberra, though often the individual thalli are no more than a few centimetres in diameter.
Also near Belconnen Way was this Trapelia , the individual thalli rather dull coloured and each no more than a few millimetres in diameter, with small, black apothecia on a few of the thalli. Here is another Trapelia species from the same site. The individual thalli are also no more than a few millimetres in diameter but this species has relatively large black apothecia. Slightly more colourful are these photos of two Lecidea species also growing on uncompacted soil and amongst grass tussocks near Belconnen Way in an area with very little threat of trampling or compaction. The thalli are greenish and the brown or black apothecia in the two photos are under a millimetre in diameter. In contrast to the habitat of those two Lecidea species, the photo on the right shows the black apothecia and pale grey to brownish thallus of Lecidea terrena, growing on bare, well-compacted soil alongside an office carpark in the Canberra suburb of Barton. During the day some people would walk through the area where this colony was growing, though it is not in a major thoroughfare. Growing with the Lecidea are some dark brown thalli of an Endocarpon species. Here are some more thalli, of Endocarpon pusillum, growing on well-compacted soil alongside a busy carpark in the Civic town centre of central Canberra. It would be very easy to overlook the dull colours of Fuscopannaria subimmixta , found growing alongside a bicycle path in the suburb of Cook. The apothecia are about two millimetres in diameter. The previous photo showed a close-up view and here is what you'd see from about a metre above the ground.
This photograph of Xanthoparmelia reptans was taken in a lightly treed area alongside a sports oval in the suburb of Kaleen. The area was patchily grassed and was not in a line between the carpark and the oval. The lichen grew in the bare soil areas amongst the grass tussocks. In more protected areas you can find colonies of the fruticose lichen Cladia aggregata .
The mushroom-like fruiting bodies of the BASIDIOLICHEN Lichenomphalia chromacea can be found in the city, sometimes in considerable numbers, on the seemingly barren soil of patchily grassed areas. As well as finding them in some parkland areas this lichen also turns up in roadside nature strips in various suburbs.
Several species of Cladonia occur in Canberra. Sometimes you will see only the sterile squamules but the upright podetia turn up often enough. This photograph was taken in an area with scattered eucalypts but otherwise little in the way of flowering plants. Most of the green is Cladonia, just the sterile squamules, with the few small, darker green patches being moss. Here is a closer view of the Cladonia squamules while the following photos show Cladonia species with brown and red-topped podetia. The CLADONIA FURCATA CASE STUDY discusses an instance where constant foot traffic inhibited podetial development in favour of compacted squamulous growth.
On roads and footpaths, rocks and walls
Canberra 's roads and footpaths are host to a small number of lichens. On various bitumen roads in the city you will find thalli of the genus Xanthoparmelia . As you walk along concrete footpaths that are at least a few years old you are likely to see what look like yellow or orange-brown stains on the concrete. Well, sometimes they may be stains but it is most likely that you are looking at lichen colonies, with the orange-brown lichens belonging to the genus Caloplaca and the yellow ones in the genus Candelariella. To see them clearly you'll need to get down on your hands and knees and look at the lichens with a hand lens. Here is a very close view of the apothecia of a Candelariella. The apothecia are up to about one and a half millimetres in diameter and dominate the view. The thallus is quite scanty. On the right is an enlarged view of part of the previous photograph. It has been enlarged to such an extent that the apothecia are a little blurry. The arrow points out a Candelariella thallus. Now that one thallus has been pointed out, you should be able to see a number of other wispy, yellowish thalli. You can also find such Caloplaca and Candelariella species on concrete roof tiles. An old, concrete-lined drain in Canberra's Haig Park supported these numerous black thalli of a species of Collema, very likely Collema coccophorum. The lichen thalli are somewhat tongue-shaped and also growing on this drain wall are numerous moss plants, curled up and dormant because it had been dry for some time.
Here is a photograph of a paved area alongside Anzac Parade in Canberra. You can see narrow gaps between the separate paving stones and the paving stones themselves have an uneven surface as you can see in this closer view . The black lens cap has a diameter of five centimetres. You can see brownish patches in the mini-depressions and several lichens grow in those depressions. The most prominent is Ramboldia petraeoides which is coloured in shades of brown with the apothecia red-brown and darker than the thallus. The more yellowish lichen in the photo is a species of Caloplaca and the bright orange Caloplaca cinnabarina is another Caloplaca species found on rock in Canberra. The wide central island between the northbound and southbound lanes of Anzac Parade has a gravel surface and is a route for occasional ceremonial marching parades. Growing on that gravel surface was this colony of Lecanora pseudistera , shown here in closer view, and nearby was this Xanthoparmelia . Several species of rock-inhabiting Xanthoparmelia are common in urban Canberra.
Rock (whether natural or used to make walls or paths) and brick support a variety of lichens in Canberra. This window ledge (right) in an office building in the suburb of Barton supports a small range of species. Here is a mixture of crustose and foliose species growing on a rock and here is another rock with several crustose species. Both rocks were part of a rock pathway in the grounds of the Australian National University. Also in the university grounds was this yellow-thallused Acarospora citrina colony on a brick wall. Rhizocarpon geographicum, a cosmopolitan species, is found on rocks in Canberra. Here is a colony and here is a closer view of this striking yellow and black crustose species. Some of the species found on roads or footpaths also grow on rocks or walls.
The trunks of isolated trees create harsh habitats for lichens since the trunks are exposed to drying by sun and wind. However, such trees can support lichen colonies and trees with fissured bark support extensive colonies. The fissures create niches in which spores or vegetative propagules can be trapped, help channel water and also provide ridges which can shade lichens for a part of each day. Numerous fissured-bark roadside and parkland trees in the older, central suburbs of Canberra are host to extensive lichen colonies. Not just live trees but also dead trees, live or dead shrubs and stumps are host to lichens and aged wooden power poles are also good substrates for lichens. Here is such a power pole in the suburb of Macquarie and it bears two easily visible lichens - the yellow, powdery textured Chrysothrix xanthina and a greenish species of the foliose genus Flavoparmelia. That power pole was also host to a number of cryptically coloured crustose lichens and you can find a variety of crustose lichens on wood in Canberra, though such species are often easily overlooked because they are typically dull coloured. Here is a closer view of a colony of Chrysothrix xanthina, this time growing on tree bark and here , with extensive Chrysothrix growth, is an old wooden seat in the grounds of the Australian National University.
One of the commonest foliose species found on wood in Canberra is Flavoparmelia rutidota. Punctelia pseudocoralloidea can be found on wood in various parts of Canberra, including street trees in the central parts of the city and this orange Xanthoria and greenish Ramalina were growing on elm trees in the suburb of Belconnen. Usnea inermis and Usnea scabrida are other fruticose species you can find on dead or live wood in the city and on charred wood you can sometimes find Thysanothecium scutellatum . Charred wood is also a substrate for Hypocenomyce australis , though it is also found on uncharred wood.
Lichens grow on a variety of other urban substrates and here are two examples. This Xanthoparmelia thallus is growing on a sunshade fabric that is sold under the trade name Sarlon and here is Amandinea punctata, growing on clear polycarbonate roofing over a patio. In both cases the thalli are about two centimetres in diameter.
Some general comments
The lichens mentioned above are simply a sample of the variety found in Canberra. The city is fairly young and was established in an area with treed hills, grassy plains and boulders or outcrops of various rock types. There are still residual areas of natural bushland within the city limits and these have provided (and still provide) homes for a great variety of lichen species, a number of which have successfully colonised the urban landscape. Canberra is still a city with a relatively clean atmosphere, so allowing a good variety of lichens to flourish. As noted early on this page Canberra has no heavy industry and so is free of the forms of pollution associated with such industries. However, parts of the city are moderately affected by motor vehicle pollution and this can have an effect on lichens. In 1993 a Canberra student carried out a brief study of lichens on tree bark in two town centres (Civic and Belconnen - about 8 kilometres north-west of Civic) and one urban control site. In contrast to the two town centres the control site had little vehicular traffic. At the time about 68% of Canberra's pollution was attributed to motor vehicles. The species found in the town centres were found also at the control site, but a couple of species found at the control site were found in no town centre. For a given species mean thallus size at the control site was always greater than that species' mean thallus size in any town centre, indicating that pollution was affecting the town centre lichens, but the study was fairly simple and allowed no detailed conclusions. .