Geoscience Reference
In-Depth Information
of nutrient cycling, and thus to an unseen world of microorganisms at work in the nas-
cent soil.
A good example of natural colonization was seen at Clipsham Quarry in
Leicestershire. Here, after about 40 years, the centre of the old quarry floor had from 5
to 12 cm depth of friable 'soil' overlying the bedrock. It contained very low amounts
of organic matter and plant nutrients - about 10 per cent as much total nitrogen, 8 per
cent as much 'available' phosphorus, and 17 per cent as much potasium as a near-by
old pasture, itself rather low in nutrients compared with most arable soils. The aver-
age yearly rainfall was also small, around 600mm, so water deficit was another lim-
itation on plant establishment. In 1980 the general appearance was of a stony, almost
barren area of ground, but closer examination showed that it supported 7 species of
mosses and 46 species of flowering plants, such as eyebright, wild strawberry, mar-
joram and bird's-foot trefoil, occupying about 8 per cent of the surface. The biomass
below the surface was probably greater than above ground, for many plants had ex-
tensive root systems seeking water and nutrients.
F
IG. 65
Quarrying exposes the parent rock. If the quarry is then disused, a new skeletal soil slowly forms by nat-
ural processes of weathering and plant colonization. Ardley Quarry, Oxfordshire (1975). (Photograph
B.N.K.D.)
