A forest in miniatureReindeer lichens (aka Cladonia and cup lichen) are a common coating on trees in
A forest in miniatureReindeer lichens (aka Cladonia and cup lichen) are a common coating on trees in the regions surrounding the Arctic Ocean, though this unusual symbiosis of algae or cyanobacteria with fungi occupy a wide variety of habitats worldwide. As their name indicates they are the only available food to the herds of reindeer and caribou during the long northern winters, and the major constituent of their diet, and the basis of the food web that keeps peoples such as the Sami alive. As well as trees, Cladonia have been found in bogs and growing on rocks, and are part of a family called ‘moss like’ lichens, though they are unrelated orgaisms.The body is a mixture of algal and fungoid cells that grip tenaciously in many life poor environments, often absorbing water and nutrients from the air or rock that they grow from, needing no soil since they have no roots. As a cooperative team each gets benefits that would not accrue to them on their own. The algae photosynthesise, sharing the nutritional benefit with the fungus, that keeps it shielded from grazers and anchored to the rock or branch amongst its fibres and gathers moisture and nutrients from the environment and substrate (whether plant or rock). There are around 20,000 known 'species’, though that term is not used when classifying them, since they are an alliance between kingdoms rather than a proper organism. By convention they are classified according to the fungal member while the green component uses its normal Linnean binomial genus and species name.Nowadays experts are coming to view them as complex ecosystems in their own right, and may include a third kingdom of bacteria within the mix. They grow slowly in harsh environments and can be very long lived. They are also the first life to colonise freshly revealed rock, say after a landslide. Their slow growth rate has been used to date events (eg by measuring seizes of lichens on tombstones with known ages to date those without any text remaining). They act as excellent environmental indicators, being very sensitive to disturbance, and have been used in fields as disparate as assessing pollution, ozone depletion (via the increased UV rays damaging the lichen) and metal contamination.LozImage credit: Matthew Cicanese/ Atkins CIWEM Environmental Photographer of the Yearhttp://1.usa.gov/1FvcWR8 -- source link
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