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3 - Further fate of organic matter in wetlands
- Edited by D. F. Westlake, J. Kvet, Academy of Sciences of the Czech Republic, Prague, A. Szczepanski, Polish Academy of Sciences
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- Book:
- The Production Ecology of Wetlands
- Published online:
- 27 October 2009
- Print publication:
- 21 January 1999, pp 169-191
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Summary
Introduction
Organic material produced by primary processes in wetlands, or imported, has various fates: part may be grazed by animals, part may be mechanically destroyed and then decomposed, part may be released into the environment during the life or after the death of primary producers, part may undergo autolysis, part may enter the detritus food chain, part may be sedimented and part may be exported out of the ecosystem. The proportion of organic matter entering these pathways may be very different in various types of wetlands.
The organic matter supports the many different kinds of organisms which feed on it, forming the base of a developed trophic pyramid. In general, it seems to be true that wetlands are typical detritus food chain ecosystems (Odum, 1971). Only relatively few animals consume the plant matter directly. On the other hand, numerous organisms feed on materials pretreated by micro-organisms, on decomposition products, and on micro-organisms carrying out the decomposition. However, qualitative and quantitative data on wetlands about the occurrence of various biota, the trophic pyramids and/or food webs related to the detritus and grazing food chains are still rather scanty. This lack of knowledge is confounded by the extreme diversity and complexity of forms and functions in wetlands.
4 - The role of decomposers in wetlands
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- By B. Úlehlová
- Edited by D. F. Westlake, J. Kvet, Academy of Sciences of the Czech Republic, Prague, A. Szczepanski, Polish Academy of Sciences
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- Book:
- The Production Ecology of Wetlands
- Published online:
- 27 October 2009
- Print publication:
- 21 January 1999, pp 192-210
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Summary
Introduction
The organic matter produced by primary producers is subject to two basic decomposition processes.
Mineralisation This accompanies the assimilation of organic matter by different organisms, varying according to the level of organisation. Some of the substances are used for building their own biomass (secondary production), but the rest is released as mineral or simple organic compounds (e.g. K+, Na+, CO2, CH4, H2O, NH4+, NO3–, SO42–, CO (NH2)2,H2S, PO43-).
Humification This is a relatively long series of various fermentative and other biochemical processes, wherein different organic metabolites become gradually transformed into complex organic heteropolycondensates with bonds of different strength, called humus. The formation, as well as the decomposition and stability, of humic substances are affected to a considerable extent by bonding with some of the mineral constituents of the medium such as ions and clay minerals.
Different ecosystems can vary in their mineralisation/humification ratio, depending on the environmental conditions and the diversity of the organisms present. Individual structures of the wetland ecosystems, i.e. standing dead, litter, bottom sediments, soil and subsoils, vegetation zones, etc., are subjected to changing conditions of water level, thermal stratification, moisture content and air humidity in the course of the growing season. The feeding materials, sources of energy for microbial populations, vary as well, and change through the trophic levels.
6 - Mineral economy and cycling of minerals in wetlands
- Edited by D. F. Westlake, J. Kvet, Academy of Sciences of the Czech Republic, Prague, A. Szczepanski, Polish Academy of Sciences
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- Book:
- The Production Ecology of Wetlands
- Published online:
- 27 October 2009
- Print publication:
- 21 January 1999, pp 319-366
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Summary
General characteristics of wetland habitats
Generally speaking, wetland plant communities are so dependent on the chemical processes in their submerged or waterlogged soils (or sediments) that they indicate the chemical properties of their biotopes.
The content of nutrients and other minerals in the aquatic environment depends on the chemistry of the parent rock, subsoil and soil and on the chemistry of the inflowing, running or spring waters. In wetland ecosystems that are managed or interfered with, such as fishponds and farm ponds or aquacultures, or polluted areas in river deltas and estuaries, the degree of either eutrophication or saprobity is decisive.
Wetland biotopes may be classified according to the limnological categories based on the relationship between mineral nutrient contents, and productivity (Thienemann, 1925; Naumann, 1932) as dystrophic, oligotrophic, eutrophic, auxotrophic (Björk, 1967) polluted and saprobic, etc. For the organisms in wetlands the physico-chemical environment, as a whole, is as important as the total nutrient concentration in the aquatic environment; and the ionic interactions (antagonism or reinforcement) are particularly important. A number of wetlands are distinguished by high concentrations of dissolved and suspended organic substances, which act as intense polyionic (macromolecular) buffer systems, functioning on a large scale, especially in the interstitial water of the bottom sediments. The limits of mineral nutrition are therefore not determined by the total nutrient concentrations, but by the absorption capacity of the relevant buffer system for each ion.