“Chain Home, or CH for short, was the codename for the ring of coastal Early Warning radar stations built by the Royal Air Force (RAF) before and during the Second World War to detect and track aircraft.
Following the development of radar at Orfordness and at the Bawdsey Research Station in Suffolk during the mid 1930’s, the Air Ministry established a programme of building radar stations around the British coast to provide warning of air attack on Great Britain. A survey was undertaken in 1938 to assess the suitability of the local terrain for Air Defence Radar operations with the first of these new stations coming on line by the end of the year. This network formed the basis of a chain of radar stations called Chain Home. These stations consisted of two main types; East Coast stations and West Coast stations.
The West Coast stations differed in layout and relied on dispersal instead of protected buildings for defence. Thus the West Coast stations had two transmitter and receiver blocks with duplicate equipment in each. Transmitter aerials were mounted on 325′ steel masts with the receiver aerial mounted on 240′ timber towers. Radar stations were soon operating at Pembrokeshire at Hayscastle, Warren near Castlemartin and Folly near Nolton to counteract low flying aircraft and ships. Chain Home Low (CHL) and Chain Home Extra Low (CHEL) were also built at St. David’s, Strumble Head, St. Twynnells (near Warren), Old Castle Head (near Manorbier) and Kete (near Dale).”
Subterranea Britannica – West Coast Chain Home and West Coast Readiness ROTOR Radar Stations
“Lichens are composite organisms in which a single species of fungus (mycobiont) lives symbiotically with one or more algal species (phycobionts), some of which may be nitrogen (N) fixing (cyanolichens), e.g. members of the blue green algae. The fungus provides structure and protection for the algae which reciprocates, providing energy and assimilates, via photosynthesis. Many secondary metabolites are synthesised by the fungus, which are unique to lichen symbioses.
Lichens obtain almost all their nutrients from the atmosphere through uptake over their entire surface. They have no cuticle, nor means of controlling nutrient uptake, unlike vascular plants, and free exchange of both gases and solutions occurs across cell surfaces. In addition their surface area to mass is very high and assimilatory capacity relatively low. Lichens are therefore highly susceptible to changes in atmospheric chemistry and deposition and for this reason provide very sensitive indicators of such changes.”
Impacts of air pollution on Lichens and Bryophytes, APIS UK