Crustose Lichen
Definition
A lichen growth form in which the thallus grows flat against and into the substrate (bone, stone, wood) and cannot be removed without damage to the substrate. Crustose species are most useful for lichenometric dating because their growth is slow, regular, and easily measured.
- Growth form
- Thallus grows flat, fused into the substrate
- Removability
- Cannot be removed without damaging the substrate
- Growth rate
- Slow and regular
- Forensic use
- Lichenometric dating of remains or exposed surfaces
Common questions
Why are crustose lichens preferred over other growth forms for dating?+
Foliose and fruticose lichens can be dislodged by wind, animals, or handling, which interrupts their growth record. A crustose lichen is fused into the substrate itself, so its diameter tends to grow at a steady, measurable rate for as long as it stays undisturbed.
How is a lichen's size actually converted into a time estimate?+
The examiner measures the diameter of the largest thallus present and compares it against a local growth-rate curve built from lichens of known age on that substrate type and in that climate, since growth rate varies by species, substrate, and regional conditions.
Related terms
- Biological Soil Crust (Biocrust)
- A community of cyanobacteria, algae, mosses, fungi, and lichens that colonises bare soil surfaces and forms a thin coherent mat. Relevant to...
- Epilithic / Epixylous Colonisation
- Growth of organisms on rock or stone surfaces (epilithic) or on dead wood (epixylous). In forensic contexts, colonisation of bone surfaces by...
- Lichenometry
- The use of lichen thallus diameter to estimate the minimum age of a surface. Based on the known or measured radial growth...
- Succession
- The predictable sequence of different insect species colonising remains as decomposition progresses. Early stages attract blow flies; later stages attract beetles, moths,...
- Thallus
- The body of a lichen, consisting of fungal hyphae housing algal or cyanobacterial cells. The thallus diameter or area is the measurement...