Life in the Soil - Soil: Reflections on the Basis of our Existence - page 69

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Spectacular bugs. Mites and springtails are the most common soil arthropods. Under the micro-
scope they look like strange prehistoric animals. The springtail ( upper left ) takes its name from
its long abdominal furcula, which allows the animal to leap into the air when threatened. Mites
are among the most diverse animal groups in the soil. Some are predators: the yellow mite with
the large front legs (top right) catches prey including springtails. Many species eat fungal myce-
lia, while others survive on dead organic material. The small yellow mites that have attached
themselves to the legs of the large beetle larva are so-called lift specialists. The larva is not
shown to scale

they digest them. This is why one does not see a thick layer of organic material
in fertile broadleaf woodland in the way one does in coniferous and nutrient-poor
deciduous forest. Deciduous forest with large earthworm populations is character-
ised by a rich understorey that may consist of high-nutrient-requiring species such
as dog's mercury, goutweed and yellow wood anemone. Nutrient-poor broadleaf
woodland, on the other hand, is often marked by a thick layer of dead leaves and
no understorey, with the slow pace of decomposition partly reflecting the absence
of earthworms.

Earthworms—Heroes in Europe, Aliens in Minnesota

Rural Minnesota in the United States was a favourite location for nineteenth-
century Swedish settlers. Until then, the Minnesotan countryside there was
earthworm-free but at some point earthworms were released to the environment,
perhaps via imported plants. The effect was devastating. Minnesota's deciduous
woods traditionally have a thick layer of organic matter aerated by beetles, mil-
lipedes and small rodents. The actions of earthworms in removing leaves from the
surface deprives these creatures of their natural environment, and the plants that
have adapted to rely on a porous layer of humus cannot grow in the hard, mineral
soil. The result is lost biodiversity and recreational value. It may seem strange that
earthworms can have such a diametrically different impact on different sides of the
Atlantic, but this is due to plant evolution, which in turn is dictated by the condi-
tions that apply in each specific spot. Environmental changes often deplete biodi-
versity, especially if the area has seen relatively little change for a long period of
time, as is the case of tropical rainforests.

Termites as Engineers

Earthworms are often regarded as the engineers of the earth due to the way their
tunnelling changes the soil structure. In the Tropics, termites perform an equiv-
alent role by transporting large amounts of organic matter to feed their larvae.
Termites exist almost exclusively on wood and one might well wonder how they