Cladonia Lichens: Nature’s Miniature Forests
This month because most plants are tricky to find and identify, we’re looking at Dartmoor’s fascinating array of montane lichens. Among the most intriguing are those from the genus Cladonia, known for their striking, miniature forest-like appearance. These lichens though inconspicuous and often overlooked, play a crucial role in Dartmoor’s upland landscape, providing habitat, soil stabilization, and even serving as environmental indicators. Let’s take a closer look at these remarkable organisms, their life cycle, habitat preferences, and where you can find them on Dartmoor.
Morphology: A Tale of Two Forms
Cladonia lichens exhibit a distinctive two-part structure. The primary thallus, which forms the base, is usually crustose (crust-like) or squamulose (composed of small, leafy scales). From this base, the secondary structures, known as podetia, emerge. These upright, often hollow stalks can take on a range of bizarre shapes—goblets, horns, cups, or even tiny, branched trees.
Many species of Cladonia develop red fruiting bodies (apothecia) at the tips of their podetia, producing spores for reproduction. This splash of colour is especially noticeable in species like the various Cladonia coccifera aggregates (Red Pixie Cup lichens) and Cladonia floerkeana (Devils Matchsticks lichen).
Life Cycle: A Symbiotic Success Story
Like all lichens, Cladonia species are a partnership between fungi and photosynthetic partners—usually green algae or cyanobacteria. The fungal component provides structure and protection, while the algae carry out photosynthesis, supplying energy.
Reproduction in Cladonia lichens occurs through both sexual and asexual means. The fungal partner produces spores from its fruiting bodies, which must encounter the correct algal partner to form a new lichen. More commonly, Cladonia reproduces asexually by breaking off small fragments containing both fungal and algal cells, which can be dispersed by wind or water.
Habitat Preferences: Thriving in Harsh Conditions
Dartmoor’s rugged and nutrient-poor landscapes provide the perfect environment for Cladonia lichens, which often colonize areas where other plants struggle to survive. They are commonly found on:
• Heathlands and bogs, growing among mosses and low vegetation
• Decaying wood, where they form part of the decomposition process
• Exposed granite boulders and soil patches, particularly in open, undisturbed areas
These lichens are particularly abundant in acidic environments, thriving in areas where heavy rainfall leaches away nutrients, creating conditions unfavourable for many higher plants.
Ecological Role: Unsung Heroes of the Moor
Despite their small size, Cladonia lichens perform several important ecological functions:
Soil Formation and Stabilization: By colonizing bare rock and soil, Cladonia lichens contribute to the gradual breakdown of substrates, forming the first layers of soil in a process called primary succession.
Water Retention: Their spongy texture helps retain moisture in microhabitats, benefiting associated mosses and other small plants.
Wildlife Support: In Arctic regions, reindeer and caribou rely on Cladonia as a winter food source. While no large herbivores in the UK depend on them in the same way, they still provide microhabitats for invertebrates.
Air Quality Indicators: Lichens, including Cladonia, are highly sensitive to air pollution, making them valuable bioindicators for monitoring environmental health.
Distribution in the UK and Dartmoor’s Hotspots
Cladonia species are widespread across the UK, particularly on montane heathlands, moorlands, and in woodland clearings. Dartmoor is one of the best places to spot them due to its acidic soils and extensive open, upland landscape. There are currently 12 known Cladonia species recorded on the moor but who knows what’s out there to be discovered!
Some likely locations to find Cladonia lichens on Dartmoor include:
Summit Tors: Look for Cladonia lichens growing on granite outcrops and amongst gaps in the clitter and boulder fields.
Upland Oakwoods: Although famous for its moss-draped oaks, Dartmoor’s ancient woodlands also harbour Cladonia species on decaying wood and rocky surfaces.
Peat Bogs: The peat-rich blanket bogs and mires of Dartmoor provide a refuge for Cladonia in their preferred acidic environment.
Heathlands: Many Cladonia species are easily spotted amongst heather and grassland across the moor, growing in association with mosses, plants and grasses.
A Tiny World Worth Exploring
Next time you find yourself wandering Dartmoor’s trails, take a closer look at the ground beneath your feet. Among the mosses, grass and heather, you might spot the intricate, alien-like structures of Cladonia lichens. These unassuming yet ecologically important organisms contribute to the wider biodiversity of Dartmoor, reminding us that even the smallest life forms can play a significant role in shaping our natural world.
Dr Luke Sutton
Image: Cladonia portentosa, courtesy of Luke Sutton