Weather: Cold, dry, clear visibility, 5C
Company:Peter Lambley, County Recorder for Lichens, Norfolk + Christopher Hitch, County Recorder for Lichens, Suffolk. Jacquie Campbell, Stephanie Hartick + others.
Species Recorded: Caloplaca flavascens, Caloplaca variabilis, Diploicia canescens, Lecanora cranulata, Lecanora dispersa, Lecanora orosthea, Verrucaria baldensis
Caloplaca favescens growing on limestone grave
Observations regarding lichen:
Variations due to following factors et al. :
geology; predominantly sandstone/carstone from Fen edge (acid) or limestone from Lincolnshire (Lincolnshire Limestone Formation, part of the Inferior Oolite Group of the (Bajocian) Middle Jurassic strata of eastern England) in St Peter’s Churchyard. The alkalinity of limestone has ability to support more species.
vegetation; lichen will grow on old wood, again aspect will play important role in determining type and spread
aspect; East facing stones tend to have damper loving lichen, table top (horizontal) slabs offer a moisture retentive, albeit warmer surface. Upright gravestones offer perches for birds and subsequent change of pH and conditions from faeces. Different coloured lichen may inhabit adjacent sections of gravestone, depending on the angle of exposure to light.
age of stones; lichen are the first living things to grow on the gravestone. The long life-span and slow and regular growth rate of some lichens can be used to date events (lichenometry). Slow but regular growth of approximately 0.1 mm radial growth a year.
form; a lichen is made up of a simple photosynthesizing organism, usually green algae or cyanobacteria, surrounded by filaments of a fungus. Most of a lichen’s bulk is made of interwoven fungal filaments. The fungus is called a mycobiont and the photosynthesising organism is called a photobiont.
reproduction; The part of a lichen that is not involved in reproduction, the “body” or “vegetative tissue” of a lichen, is called the thallus. The thallus form is very different from any form where the fungus or alga are growing separately. The thallus is made up of filaments of the fungus called hyphae. The filaments grow by branching then rejoining to create a mesh, which is called being “anastomose”, this mesh may be dense or loose.
structure; The top layer, where the lichen contacts the environment, is called a cortex. The cortex is made of densely tightly woven, packed, and glued together (agglutinated) fungual filaments.The dense packing makes the cortex act like a protective “skin”, keeping other organisms out, and reducing the intensity of sunlight on the layers below. Cortex layer can be up to several hundred micrometers in thickness (less than a millimeter).
identification; use of chemicals such as bleach, iodine, potassium hyrodoxide as a spot test to aid identification of species.
potassium hydroxide spot test added to lichen, turning purple/red
growth; lichen produce their own food by photosynthesis using sunlight as energy, from carbon dioxide, water and minerals from their environment. Lichen are capable of surviving extremely low levels of water content (poikilohydric). They will quickly absorb water once available again becoming soft and fleshy.
colour; colours of lichen determined by photosynthetic component. Special pigments such as yellow using acid give lichen a variety of colours including an array of red, brown, oranges. In the absence of special pigments lichen are usually bright green to olive gray when wet, gray or greyish green when dry. This is because moisture causes the surface skin (cortex) to become more transparent, exposing the green photobiont layer. Colour descriptions when used for identification are based on when the lichen is dry.
The underside of the leaf-like lobes of foliose lichens is a different color from the top side (dorsiventral), often brown or black, sometimes white. A fruticose lichen may have flattened “branches”, appearing similar to a foiliose lichen, but the underside of a leaf-like structure on a fruticose lichen is the same color as the top side. The leaf-like lobes of a foliose lichen may branch, giving the appearance of a fruticose lichen, but the underside will be a different color from the top side.
The sheen on some jelly-like gelatinous lichens is from mucusy excretions.