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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.
