Seite 30 [30]
28 | II. Biocoenosis and zoocoenosis
“the biocoenosis of a forest” because the forest, (if we understand a forest as
only trees and undergrowth), is not a biocoenosis in the same way that the
animals living in the forest are not yet a biocoenosis, nor is the sum of these
two a biocoenosis, but both are members of a biocoenosis that also includes
fungi and bacteria living there.
The biocoenosis is consequently an association of living beings, whose
members are in functional relationships with each other, forming a very
complex unit of living organisms, and its complete, real-time perception is
nearly impossible.
The members of a biocoenosis, more correctly its living members, are
usually classified into three groups: producing, consuming and reducing
elements (Thienemann, 1939). If, however, we define a biocoenosis as the
whole association of living beings, this theoretically correct three-way
classification is insufficient. The plant kingdom does not only comprise
photosynthesising green plants, but also organisms that are unable to assimilate
CO,, and ones that are dependent on already-synthesised organic materials.
The producing organisms therefore produce organic material not only for
animals, but also for certain plants, so the consumers are not exclusively
animals; they include certain organisms classified as plants.
So, after all, what organisms constitute a biocoenosis? Firstly, living things
able to produce organic compounds from inorganic ones (producers). To
these are added organisms that need already-synthesised organic material,
and these can be either plants or animals. Some of these rely on plants, others
on living animals (corrumpents and obstants), while still others utilise organic
materials in a non-living state (intercalary elements). There are living
organisms that sustain others (sustinents) and, finally, organisms that convert
organic materials into inorganic matter (reducents).
Consequently, we recognise the following groups when we want to unearth
the structural elements of a biocoenosis:
1) Producents include plants that synthesise organic compounds, either
by photo- or chemosynthesis, and which are the basis of all other life forms.
Without them, no biocoenosis can be formed.
2) Corrumpents are the plants or animals that utilise other living plants
(producents or intercalary element).
3) Intercalary elements (recuperants, sensu Woynarovich 1954) are plants
or animals that are dependent on existing organic compounds, but assimilate
them in their non-living form.
4) Obstants are plants or animals that live at the expense of other living
organisms (plants or animals) as parasites or predators.
5) Sustinents are plants or animals that contribute to the survival of others,
either as symbionts or as agents of reproduction, thus fulfilling a vital function
in their survival.
6) Reducents are plants that decompose organic material into inorganic
compounds.