Why do lichens survive alongside roads

Mosses are simple plants both anatomically and morphologically. Growth in mosses is much less polarised than in vascular plants; dormancy or death of the growing point can stimulate buds further down the stem. Many mosses have root like structures, rhizoids and some mosses, like vascular plants, can be considered as calcifuges or calcicoles, favouring acid or calcareous conditions respectively. Mosses can grow in a range of habitats, even extreme with respect to climate and some species show remarkable tolerances to heavy metals, e.

These mosses trap and concentrate these metals, absorbing them both from the atmosphere and the substrate over their large surface area.

Like lichens, mosses derive nutrients from atmospheric deposition but, by comparison with lichens, are less dependent on this nutrient source. Too much N can change morphology, often leading to sparser mats that are desiccation prone and less efficient at suppressing competitors e. Racomitrium lanuginosum , Armitage et al ; photosynthesis can be compromised along with membrane integrity and sexual reproduction may also be suppressed.

Mosses play an important role in nutrient cycling; immobilization of N in some habitats, e. However, the ability to sequester N depends on the N load and systems can soon be saturated. Some mosses including those growing on bogs, Sphagnum spp. Studies have identified both N sensitive and N tolerant mosses. Pleurozium schreberi has been shown to be N sensitive in several studies Solga et al ; Sheppard et al and appear to have a threshold N concentration, benefiting from modest inputs that do not raise the N concentration above the threshold.

Species within the important peatland genera Sphagnum show a range of tolerances to N; pool species appear to be the most tolerant, probably reflecting the lower ionic concentrations in these wet environments, while hummock formers are the most N sensitive.

In situ N manipulation studies on S. The responses of mosses and other bryophytes growing in Atlantic oakwoods, a relatively pristine environment, to increased N deposition has been examined by Mitchell et al ; ; Hypnum cupressiforme cypressleaved plait-moss and Hypnum andoi mamillate plait-moss were relatively tolerant.

Stevens et al used data from eight national vegetation datasets to look at acid grasslands, calcareous grasslands, heathlands, and bogs in the uplands and lowlands. A European survey Harmens et al. They recommended that these mosses could be used to provide reliable estimates of N deposition, providing a useful and relatively cheap methodology. However, interpretation of such data needs to take account of the form of N and the local climate. Deposition of reduced N, especially dry deposited NH 3 causes the highest N concentrations in moss tissue, followed by wet reduced N and oxidised N.

At high N doses wet reduced N leads to significantly higher N concentrations than oxidised N Sheppard et al The European survey also measured herbarium specimens from across Europe and found that moss N concentrations started to increase noticeably from Skip to main content. Home Issues Impacts of air pollution on Lichens and Bryophytes mosses and liverworts. Impacts of air pollution on Lichens and Bryophytes mosses and liverworts.

Lichens Characteristics and background Lichens are composite organisms in which a single species of fungus mycobiont lives symbiotically with one or more algal species phycobionts , some of which may be nitrogen N fixing cyanolichens , e. Some lichens look like miniature branching bushes; some, a flaky, papery crust; others have long, hanging hairs, or tiny little cups, or just look like a powdery coating. They can be mistaken for moss, which is a plant that grows in similar locations, but mosses are not related to lichen.

Some lichens grow relatively quickly, up to a few feet per year, and some extremely slowly, expanding only by a millimeter or so each year. They come in about every color, green, blue, and occasionally are red or yellow. There are at least 18, species of lichen, each a unique combination of fungi and algae or cyanobacteria.

Algae are a large group of plants that range from seaweed to single-celled organisms, but the main species found in lichen is green algae. Cyanobacteria formerly known as blue-green algae can also occupy this role in the fungi-algae partnership. As lichens die, they contribute to decayed organic matter to the area they inhabit, which enables mosses and seeds from vascular plants to begin developing among the pockets of new soil.

Animals utilize lichens in many interdependent ways. It is well documented that numerous animals use lichens for food or shelter. Around 50 species of birds are known to regularly use fruiticose lichens as their preferred nesting material. Small animals commonly use lichens to hide from natural predators through camouflage and direct cover. CFAES provides research and related educational programs to clientele on a nondiscriminatory basis.

For more information, visit cfaesdiversity. For an accessible format of this publication, visit cfaes. Skip to main content. Agriculture and Natural Resources. Jim A. Chatfield, Sarah D. Williams, Thomas K. Mitchell and Michael J. What are lichens? What do lichens look like? There are four basic lichen body types: 1. Lichens in the open would obviously benefit from both direct rainfall and runoff from any higher areas.

Runoff can drip from shrubs, be channelled down trunks or flow down angular boulders and a little way around their underside before dripping to the ground.

Therefore lichens in microhabitats sheltered by vegetation or suitably shaped boulders could also make use of runoff. To use dew lichens would need to be out in the open, where the dew condenses overnight. Similarly, fog utilization requires thalli to be in the open where they can intercept the incoming fog. A number of species appear to have different rates of water uptake for upper and lower thallus surfaces, with the rates higher for the latter.

Fogs can occur in arid inland areas but there are various coastal fog deserts where numerous fogs occur each year, are the major source of water and lower the temperature. Depending on winds and topography the effects of such coastal fogs may extend many kilometres inland and, in some locations, produce sufficient moisture to support the growth of vascular plants.

An example is the Namib Desert which borders the Atlantic in south-west Africa and is one of the driest areas on earth. It extends north-south for over kilometres and, in parts, to over kilometres inland. Given the desert's latitudinal range and its varied topography it's not surprising that precipitation also varies depending on location.

One general comment is that there is little rain. Average annual rainfall can be as low as seven millimetres in some coastal areas to over 60 millimetres well to the east. However there are coastal fogs with the number of foggy days per year ranging from a few to well over in some parts and fog precipitation varying from very little to at least millimetres per year. The greatest benefits of fog are experienced near the coast but the effects can sometimes be felt well inland.

On at least one occasion a desert scorpion has been seen harvesting water from a grass tussock at a research station 60 kilometres inland. The fog was still quite dense at the research station and extended further inland. Fog precipitates on any raised surfaces, such as grass tussocks, shrubs, rocks - and various lichens. Namibian landscape with orange Teloschistes dominant. Fog precipitation allows a variety of lichens, including various foliose and fruticose species, to grow in many parts of the Namib Desert.

This photo right shows an abundance of a fruticose Teloschistes species on a Namibian coastal plain. Several Teloschistes species occur in Namibia. All of the red-brown areas in that photo are Teloschistes and here is a closer view showing Teloschistes and various other lichens. Upright growth coupled with a large surface area is the way to maximize moisture extraction from fog and fruticose species such as Teloschistes are therefore very effective at trapping fog moisture.

A crustose thallus growing on a vertical surface facing into the fog would be well-positioned to make use of fog moisture whereas a crustose thallus on the ground would be less efficient at extracting moisture from fog.

It is interesting to note that in the northern Namib Desert thalli of some crustose species showed adaptations to fog. Upturned margins were found on thalli of Caloplaca elegantissima and Caloplaca namibensis and a bunched, rather than flat, growth form of Lecidella crystallina was found. Such forms would better intercept and absorb fog moisture than would a totally flat thallus. The coastal deserts of Peru and Chile are also amongst the driest areas of the world.

Cloud edges may reach this area and the only source of moisture is what can be trapped from the moving clouds or fogs. The authors added:. The lichen clumps, three decimetres or more in diameter and eight centimetres high, are easily picked up from the ground. Most are of the bright-orange dominant Teloschistes peruensis.