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positions occupied by various small arthropods; A = bristle-tail, B = springtail, C = woodlouse. The tem-
perature decreases from the top downwards while the relative humidity increases. When the stones are
shaded, the bristle-tails move to the underside of the upper stone layer. (Adapted from G. Eisenbeis 1983.)
Cracks and fissures in the ground serve much the same function as stones in af-
fording protection from dry conditions for species that cannot burrow for themselves.
Cracks are a common feature of clay soils during the summer, and may penetrate a
foot or more in grassland or arable fields.
Plant cover affects conditions on the soil surface in more ways than inorganic
objects do because of its more varied and complex structures and thermal properties.
Adhering vegetation, such as moss and algae, liverworts and lichens, harbours a rich
micro-fauna of protozoa, nematodes, tardigrades, small mites and springtails. Larger
moss cushions, grass tufts and rosette plants shelter a wealth of small beetles and oth-
er insects, both adults and larvae. Dead plant material not only gives shelter but offers
food for a wide range of animals and fungi which fulfil a vital role in returning the
store of organic material and nutrients back to the soil.
F IG. 2
Leaf litter, twigs and branches in a mixed oak/ash woodland in spring. Note that oak leaves remain but all
the ash leaves have disappeared. (Photograph B.N.K.D.)
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