Though they are not
classed as limestone, a number of other rock formations scattered
over the lowlands of Britain give base-rich or even calcareous
substrata which carry unenclosed grassland or open rock
communities. Various types of sandstone, shale, greywacke, schist,
gneiss, and igneous rock locally contain enough calcium carbonate
to give soils which are calcareous, or at least base-saturated, and
where these occur in lowland situations they frequently bear
grasslands of obvious floristic affinity to those found on the real
limestones, though not falling within the strict definition of
'calcareous'. The richer examples of these grasslands are similar
in floristics to those of Chalk and Limestone, but some species are
characteristic of soils with only moderate calcium status derived
from less rich parent materials, e.g. Ranunculus acris, Viola
riviniana, Trifolium campestre, T. dubium, Fragaria vesca,
Saxifraga granulata, Gentianella campestris, Galiumverum, Bellis
perennis, Achillea millefolium, Hieraceum pilosella and Agrostis
tenuis. Open places on dry basic soils in general have species such
as Arabidopsis thaliana, Arenaria serpyllifolia, Veronica arvensis
and Sherardia arvensis.
Often, on these
other geological formations, the parent rock is not sufficiently
calcareous to resist leaching, so that the areas of base-rich soil
tend to be small and mav be restricted to flushed ground. The most
important examples are found in Scotland, on such formations as the
Silur!_ greywackes and shales of the Southern Uplands, the
Dal-radian schists of the southern Highlands, the Old Rti Sandstone
of north-east Scotland and Orkney, and d Tertiary basalts of the
western Highlands and islands. I: few places they include limited
areas of a real limes: r E such as that forming the island of
Lismore in the F Lome.
Many of these
northern occurrences of calcareous rock support communities which
are of upland rather than lowland affinity. In places where there
are grassla: recognisably lowland character these seldom appear to
be of I sufficient importance to warrant separate consideration,
and examples are usually represented within sites rated high for
their other formations. However, certain localities Kr considerable
interest for their flora. In particular, there several occurrences
of igneous rock, mainly dolerite. ar related material, which
support not only calcicolous r.--".s but also others with evidently
unusual mineral requirerr.c Stanner Rocks in Radnor and Breidden
Hill on the bo:: of Montgomeryshire and Shropshire are among known
of such outcrops. The second is famous for the rare Potentilla
rupestris and both have other rare such as Lychnis viscaria,
Veronica spicata ssp. hyb~ Sedum forsteranum and Bartramia stricta,
mixed with c common calcicoles. Arthur's Seat, Salisbury Cr .
Blackford Hill in Edinburgh have L. viscaria, Vicia sykc: Dianthus
deltoides, P. tabernaemontani and Asplenium trionale, and Traprain
Law in East Lothian has severa. mosses, especially of the genus
Grimmia. The slopes ing some of these sites have species-rich
grasslands, are seldom as varied as examples on real limestone. T
igneous rocks often provide important quarry stone, several of the
best sites have been spoiled. Breiddei: was probably the most
important but has deten:: greatly through quarrying. Both this site
and Stanr.-. -also have woodland affinities (see
Appendix).
Submaritime
grasslands which have affinities with rim lowland calcareous
grasslands (e.g. the Hebridean macr are dealt with in Chapter
4.
