Hidden forests of lichen

WildNet - Jim Higham

While out on your daily exercise close to home, hidden forests of lichen are waiting to be discovered. They thrive in almost any environment with enough light, from the rocky mosaics of dry-stone walls to the gnarled bark of ancient trees. Woodlands during winter have so much to offer those brave enough to face the cold. Take a trip to your local woods this winter and see whether you encounter lichen on your walk.

Lichens are bizarre but fascinating things — made up of two tiny plant-like living things: a fungus and an alga. These organisms have a symbiotic relationship, which means that they benefit from living together. They live in harmony, the fungus providing structure and the alga making food through photosynthesis. This is a chemical reaction that takes place through the use of carbon dioxide, water and light to produce food for the organism to survive. They’re often overlooked, but closer inspection reveals a world in miniature, with lichens growing in sprawling shapes like the trunks, branches and leaves of the forests in which many of them grow. It seems as if no two lichens are alike, each patch a work of chaotic art, from moss-green cups to rust-coloured mats. With a searching eye and an open mind, lichens can brighten any walk in the wild if you can find some close to home.

Occurring from sea level to the peaks of mountains, lichens can grow on almost any surface. Lichens are not parasitic, and so they do not harm any plants that they grow on. They are in fact very useful to their neighbouring wildlife, providing material for bird’s nests as well as food and shelter for bugs and small creatures. Encrusting as much as a staggering eight percent of our planet’s surface, they shroud an area larger than the that covered by tropical rainforests. Not simply limited to stationary hosts, lichens can be found to live on beetles and other insects, acting as crucial camouflage for these tiny creatures. On the other hand, solitary untethered lichens roam the land, blowing around the environment like tumbleweeds. Some variants have even been found to live inside of solid rock, growing between the tiny grains. Lichens may be plant-like, but they are not in fact plants. Similar to moss, they have no roots to absorb water and produce nutrition through photosynthesis.

Appearing as crusty peeling paint, dainty and leaf like structures or as draping bushy beards, lichens take many forms and are spectacular in their appearance. There are many variations in their coloration depending on the habitat. Taking on shocking reds and striking yellows in exposed and dry locations, lichens are luminous green to an olive grey in wet and humid environments. As they are also sensitive to pollution, their appearance can reflect the quality of the surrounding air. Lichens hardier to pollution are typically crustier, whereas the rarer variants resembling delicate beards are found living in cleaner air.

The relationship between ancient woodland and lichens is a crucial one. These are woodlands that have persisted for centuries, harbouring complex communities of lichens, fungi and plants as well as being home to an abundance of animal life. Lichens depend on these aged habitats as they require a long time to develop, growing only one to two millimetres a year. These woodlands only cover 2.5 percent of UK land, but are irreplaceable habitats that have taken hundreds of years to establish.

Some species of lichen require high levels of alkaline that are found only on older bark, as bark becomes more alkaline with age. Ash is a species of tree high on the pH scale and so has high alkalinity. This is a scale used to measure acidity from 0 to 14. It tells how acidity or alkaline a substance is. More acidic solutions have a lower pH, and more alkaline solutions have a higher pH. There are an astonishing 536 species of lichen that are associated with the ash tree. This helps us to gain perspective on just how important a singular ancient tree can be in providing a home for diverse species of lichen - echoing the relevance of protecting our remaining ancient woodlands in maintaining biodiversity.

The longer you look, the stranger they become! Now that you have gained an insight in to the captivating and mysterious world of lichens, you can take some time to spy this curious organism whilst taking your local daily exercise close to home.

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