OTHER SOIL ANIMALS - The Soil - page 118

red and false colour aerial photographs which detected the incorporation of surface
organic matter into the soil.
Insects, by contrast, were able to colonize the polders very quickly by flying in
from agricultural areas on the mainland. Sixty-seven species of ground beetles were
caught in traps in the southern-most polder, Zuidelijk Flevo-land, within a year of its
being finally drained. A dozen species were able to overwinter and breed in the newly
laid out road verges so there would have been a well developed soil insect fauna long
before moles invaded an area.
Mole-hills have significant effects on vegetation but not in quite the same way
as ant-hills. Mole-hills are a sudden extrusion of bare soil breaking the otherwise con-
tinuous plant cover. The soil may differ somewhat from the topsoil if it has come from
some depth, but the texture has not been altered as it has in ant-hills. Fresh mole-
hills therefore offer sites for seeds to germinate without competition from established
plants, and so allow short-lived plants to maintain themselves in a sward.
A.S.Watt's long-term studies on ungrazed grassland on Foxhole Heath in Nor-
folk showed that there was a cycle of change, and that this cycle was caused by mole-
hills. Watt recognized four stages in the cycle which he called 'pioneer', 'building',
'mature' and 'degenerate' phases. During the succession through these phases, it was
apparent that eroded mole-hills were dominated first by annual species, and then by
perennial herbs, before entering the mature phase with relatively few species, mainly
perennial grasses. The degenerate litter-covered phase of dead grasses was colonized,
not by annuals of the pioneer phase, but mostly from neighbouring plants - unless the
cycle was restarted through the action of moles.
This plant community at Foxhole Heath included five of the rarer Breck-land
species: Spanish catchfly Silene oliles and spiked speedwell Veronica spicata char-
acteristic of the building phase, and sickle medick Medicago falcata , Bohmer's cat's-
tail Phleum phleoides and the sedge Carex ericetorum , characteristic of the mature
phase. Their relative frequency, if not their very presence, was largely dependent upon
moles.
Moles, like ants, also provide niches for subterranean invertebrates. Several
species are found in rabbit and small rodent burrows also, but at least ten species
of beetles are considered to be specifically associated with mole nests and runs.
W.J.Fordham and R.C.Welch have independently recorded the following: Aleochara
spadicea, Hister marginatus , Quedius nigrocoeruleus, Q. longicornis, Q. othinensis,
Oxypoda longipes, Pycnota paradoxa, Eccoptomera nigra and Medon castaneus.
None has attracted wide enough attention to gain a common English name.