NATURAL HABITATS - The Soil - page 155

more widespread plant communities. In this example, grazing livestock, moles and
soil macro-fauna all influence the soil condition as well as react to it.
Mole activity was considered in chapter 5 but, in concluding this look at the bio-
logical features of the soil on moors and hills, we can summarize a regional study of
mole distribution on open hill grazing in northern Snowdonia. As we said earlier, the
frequency of mole-hills is not a sure guide to mole numbers. However, in this upland
environment which is generally low in nutrients, mole-hills are a conspicuous indic-
ator of soils that are fertile enough to support earthworms and therefore a grassland
community more favoured by sheep. In the Snowdonia study, mole-hills were recor-
ded (as either present or absent) in an extensive series of contrasting areas established
for a sheep grazing census. Out of 48 study areas, 19 had mole-hills, and, in these,
the soils were all Brown Earths or Brown Podzolic Soils. They had surface horizons
of mull humus or were intermediate between mull and moder, with a mean pH of 4.8.
Most sites without evidence of moles had soils with peaty surface horizons and were
significantly more acid, with pH around 4.3. A few sites were suitable for worms but
could not support moles because their very stony soils prevented tunnel construction.
G RASSLAND HABITATS
Within these generally infertile moorland and hill habitats, the grasslands that occur
on Brown Earth soils over base-rich rocks can be considered as islands. But even in
the lowlands, semi-natural grasslands have become scarce features. The limited areas
that remain are virtually all within conserved sites. Communities of native species
which simulate old grassland may be re-established on land that is 'set aside' under
present agricultural policies. However, the creation of natural grassland soils would
need many times the five year period at present allotted to the scheme, as the next
example shows.