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ECOLOGY OF THE GROUND |
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The
fauna of the ground |
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The macrofauna
is made of animals whose size is greater than 10 millimetres, represented
especially by mammals, annelids and insects. Among the former we mention
rodents, always detrimental to cultivations and moles detrimental to roots,
but also useful as insectivorous. Annelids, particularly the earth-worms,
have an important positive effect over the characteristics of the ground. Their
action of constant mixing and airing of soil, together with the filling up
with earth (covering with earth) and the partial digestion of organic
substances, helps also the attack from the micro-organisms which are
transported and spread by the earth-worms. A few insects of the ground are
certainly detrimental as phytophagans, while some others like rove
beetles feed phytophagans; others as spring-tails and social insects (
ants and termites), many dipterans and coleopters have an important function
in the interment and the breaking up of organic residual products. The microfauna
is characterized by a size inferior than 0,1 millimetres and it is
essentially made of Protozoa, unicellular organisms which use organic
substance and they frequently live chargeable to bacteria and fungus with an
important limiting effect. |
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The mesofauna
is made of animals whose size is between 0,1 and 1 millimetre inclusive,
among which spring-tails in particular , then arachnida (spiders and acari)
which carry on actions similar to those of insects. Nematodes are often
parasites of cultivated plants, but there are lots of species that feed on
substances in decomposition, helping the evolution or else they live
chargeable to microflora, contributing to its balance. |
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the
flora of the ground |
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The
microflora constitutes the most remarkable part in the biomass of the ground,
both for quantity and biologic developed functions, in fact in a gram of
ground from a million to 10 and more thousand millions of bacteria remain,
they are unicellular organisms sometimes joined in colony. The feeding
classification allows to divide them into three big groups acting as the
source of utilized energy: the photoautotrophics are able to derive
the energy from the light, through the chlorophyll, likewise to the superior
plants; the chemoautotrophics derive the energy from reactions of
transformation (oxidation) concerning inorganic substances (sulphur, ammonia,
nitrites, iron and manganese); the heterotrophics, the most numerous,
feed on the organic substance of the ground, which they decompose with the
production of energy. Fungus is another important element of the microflora;
its action is essential for the degradation of many organic substances and
particularly of lignin; often it joins the roots, forming the mycorrhiza,
which expand both the absorbing surface of the plants and their feeding
capacities. Actinomyces, intermediate micro-organisms between bacteria and
fungus, generally have a good activity of degradation as regards particular
organic molecules attackable with difficulty (for ex. aminoacids), besides
they have a considerable function in the production of vitaminic, antibiotic,
hormonic and hormone-similar substances. Algae, especially present on the
surface of the ground, form organic substance and they fix the azote. Classifiable
in the microflora, virus are sometimes pathogenous for the cultivations, but
many times they are factors of limitation and balance for the other
micro-organisms. The macroflora is represented essentially by the roots of
superior plants and by lichens, important especially in the growing grounds
or in not so developed ones. |
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Food
chain |
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Usually
the first attack to the organic substance which comes to the ground, is
produced by macroflora which disintegrates, moistens and takes it to the
depths. The meso and microfauna continue the activity; at the same time and
after the different groups of bacteria, fungus and actinomyces, feeding on
specific molecules, operate. As we have already seen, the fauna and the flora
of the ground are then parasitized or plundered by the different specific
components present in each group. So the addition of organic substance starts
an explosion of life, whose process is slow at the beginning, but it roughly
accelerates because of a very rapid growth of microflora and suddenly it
drops when the favourable conditions fail it. In fact the different stocks of
micro-organisms are extremely specialized both as for the food sources and as
for the environmental conditions. Consequently in case of crisis they die or
they move to stadia of latent life. This is a very frequent event, helped
also by their scarce mobility which doesn't let them reach the zones of
ground where they could keep on growing. Taken from "Agricoltura biologica" supplement to n.6 1998 Notiziario ERSA, Gorizia IT. |
