Biological Soil Crust (Biocrust)
Definition
A community of cyanobacteria, algae, mosses, fungi, and lichens that colonises bare soil surfaces and forms a thin coherent mat. Relevant to forensic botany because biocrusts colonise exposed soil and sometimes bone surfaces on or near surface remains.
- Composed of
- Cyanobacteria, algae, mosses, fungi, lichens
- Habitat
- Bare, undisturbed soil surfaces
- Forensic use
- PMI estimation from colonisation on remains or soil
- Field
- Forensic botany
Common questions
How does a biocrust help estimate time since death?+
Biocrusts colonise exposed surfaces gradually, so the extent of crust development on soil disturbed by a burial or on bone left exposed provides a rough minimum time since the disturbance or exposure occurred, comparable in principle to using plant regrowth as a PMI indicator.
Why is biocrust evidence considered a rough indicator rather than a precise one?+
Colonisation rate depends heavily on local climate, moisture, and soil type, and biocrust species vary regionally. Without a site-specific growth-rate baseline, the estimate typically yields a broad time window rather than a tight PMI figure.
Related terms
- Crustose Lichen
- A lichen growth form in which the thallus grows flat against and into the substrate (bone, stone, wood) and cannot be removed...
- 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...