What is the difference between autochthonous and allochthonous

Autochthonous is a term that refers to sediments that are found in the same place where they were formed or in a location very close to its site of deposition. Therefore, autochthonous sediments or autochthonous rocks are found in their native place. Furthermore, they are buried in a place without disturbance or disarticulation. Indigenous is a synonym of autochthonous.

Many fossils are obviously autochthonous. Parautochthonous is a term that refers to sediments that show characters intermediate between autochthonous and allochthonous. Therefore, parautochthonous sediments or rocks are formed from materials that have been transported or displaced a relatively short distance. Allochthonous refers to sediments that are found remote from the place of origin, while autochthonous refers to the sediments that are found in the same location where they have formed.

Parautochthonous, on the other hand, refers to sediments that have been transported or displaced a relatively short distance and have an intermediate character of allochthonous and autochthonous. So, this is the key difference between allochthonous autochthonous and parautochthonous. The sediments are displaced in allochthonous, but in autochthonous, the sediments are not displaced from the site of origin.

However, in parautochthonous, sediments are displaced a relatively short distance. Allochthonous, autochthonous, and parautochthonous are three terms used in geology to refer to the origin of sediments. Allochthonous refers to sediments that are buried or found in a place remote from the site of formation. Autochthonous sediments are buried in a place where they have formed or originated without disturbance or disarticulation.

Parautochthonous refers to the sediments having a character intermediate between that of autochthonous and allochthonous. Parautochthoonous sediments have displaced a relatively short distance from the place of origin.

Thus, this is the summary of the difference between allochthonous autochthonous and parautochthonous. Bird, John M. Samanthi Udayangani holds a B. Degree in Plant Science, M. After Zheng et al. However, a substantial proportion of the organic matter in aquatic communities comes from allochthon-ous material that arrives in rivers, via groundwater or is blown in by the wind. The relative importance of the two autochthonous sources littoral and planktonic and the allochthonous source of organic material in an aquatic system depends on the dimensions of the body of water and the types of terrestrial community that deposit organic material into it.

A small stream running through a wooded catchment derives most of its energy input from litter shed by surrounding vegetation Figure Shading from the trees prevents any significant growth of planktonic or attached algae or aquatic higher plants. As the stream widens further downstream, shading by trees is restricted to the margins and autochthonous primary production increases. Still further downstream, in deeper and more turbid waters, rooted higher plants contribute much less, and the role of the microscopic phytoplankton becomes more important.

Where large river channels are characterized by a flood plain, with associated oxbow lakes, swamps and marshes, allochthonous dissolved and particulate organic may be carried to the river channel from its flood plain during episodes of flooding Junk et al. The sequence from small, shallow lakes to large, deep ones shares some of the characteristics of the river continuum just discussed Figure A small lake is likely to derive quite a large proportion of its energy from the land because its periphery is large in relation to its area.

Small lakes are also usually shallow, so internal littoral production is more important than that by phytoplankton.

In contrast, a large, deep lake will derive only limited organic matter from outside small periphery relative to lake surface area and littoral production, limited to the shallow margins, may also be low. The organic inputs to the community may then be due almost entirely to photosynthesis by the phytoplankton. The different symbols in each panel relate to different forests. Daily GPP is expressed as the percentage of the maximum achieved in each forest during days of the year.

After Falge et al. Estuaries are often highly productive systems, receiving allochthonous material and a rich supply of nutrients from the rivers that feed them. The most important autochthonous contribution to their energy base varies. In large estuarine basins, with restricted interchange with the open ocean and with small marsh peripheries relative to basin area, phytoplankton tend to dominate.

By contrast, seaweeds dominate in some open basins with extensive connections to the sea. In turn, continental shelf communities derive a proportion of their energy from terrestrial sources particularly via estuaries and their shallowness often provides for significant production by littoral seaweed communities.

Indeed, some of the most productive systems of all are to be found among seaweed beds and reefs. Finally, the open ocean can be described in one sense as the largest, deepest 'lake' of all.

The input of organic material from terrestrial communities is negligible, and the great depth precludes photosynthesis in the darkness of the sea bed. The phytoplank-ton are then all-important as primary producers. Continue reading here: Variations in the relationship of productivity to biomass. Ecology Center Alternative Energy current.