Parmelia Sulcata Lichen or shield lichen, is a lichen in the family Parmeliaceae. It is very tolerant of pollution and is widespread, making it one of the most common lichens. The thallus is formed of flat, blue grey lobes up to 20 cm in diameter that grows on bark, widespread and common on trees in open habitats and occasionally on rocks.
A lichen is created when a fungus and algae join together to form a new organism. This relationship between the fungus and algae is not yet fully understood, but studies are being done to learn more.
Although they look like plants, lichens do not have roots, stems, or leaves. The lichen takes the form of the fungus, and the algae lives inside. Since most algae are plants, they can make their own food. The fungus part of a lichen gets its food from the algae. This may be a mutualistic relationship, since the fungus gets food from the algae, and the algae gets a home from the lichen.
Lichens are not a usual food item for animals, but some that are known to eat them, these include deer, snails, some birds, voles and some insects. Lichens, provide homes for tiny animals and some larger animals can use them as shelter or cover, such as spiders, insects, and lizards. Hummingbirds will use lichens to line their nests.
Lichens grow very slowly. If a part of the lichen is broken off, it can grow into a new lichen. Lichens also make spores which can travel to new places on the wind; however, the spores will only grow into a fungus, not the total lichen.
Over time, lichen can break down rocks and put nutrients back into the soil.