[from Greek abíotos, non living]. In ecology it is said of an area or part of soil, place, etc. not populated by any living organisms, or of a non-living component of any ecosystem. Such abiotic component of every ecosystem is represented by a series of factors that, even if not belonging to the living world, allows its development. Among these, one can list climatic parameters, as pressure, temperature, humidity, the presence of inorganic substances in a gas state, the availability of both inorganic and organic compounds which may be present in the ground and in the water. While the climatic system is essentially immodifiable, the other abiotic factors are closely linked to the possibility of recycling material coming from other living beings both inside the same ecosystem, and through exchange with others. In this context the abiotic elements involved to a greater extent are carbon, nitrogen, phosphorus, as they are essential chemical components to the biotic component of any ecosystem. The carbon is taken from the atmosphere, in which it is present in the form of carbon dioxide, from plants, seaweeds and cyanobacteria that fix it through the photosynthesis in organic compounds: the fixing allows carbon to move from the abioic environment to the first step of all food-chains. The nitrogen, an essential protein component, is present in the atmosphere in a large quantity (about 78%) but in its molecular shape, N2, can be employed only by some bacteria, therefore called nitrogen fixers. They are able to carry out the chemical transformation of the atmosheric nitrogen into ammonia (NH3), and then into nitrites(N02) and into nitrates (N03). In this new molecular shape the nitrogen can be employed by vegetables that often establish symbiotic relationships with the nitrogen-fixing bacteria. The phosphorus, an essential element for many cellular structures and functions, is present as an abiotic element in the mineral world in the form of phospates. The rainwater, causing the erosion and translocation of the phosphates, makes them deposit on the ground, where they will be able to be absorbed by the plants, or reach the sea basins; in this case they can go back to the land, through water flora and fauna, through the faeces of the waterfowls. More generically we can therefore state that matter moves from the abiotic environment to the living organisms to go back there with their droppings or at the end of their living cycle.
Source: De Agostini - Sapere.it