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Wetlands: Freshwater
Published in Yeqiao Wang, Wetlands and Habitats, 2020
Wetland is the term used since the late 1960s for a very large diversity of habitats that were previously known by common terms such as bog, fen, mire, marsh, swamp, and mangrove and hundreds of local names in different countries. Wetlands occur in all climates, across a wide range of latitudes, and from sea level to more than 5000 m altitude (as in the Himalaya). The unifying characteristic of these areas on the Earth’s surface is that the land remains either water-saturated or under shallow water for a period ranging from several weeks to the whole year and is generally covered with vegetation that differs from that in the adjacent areas (see also[1]). Wetlands are sometimes transitional in character between deepwater and terrestrial habitats, and are often located between them. These habitats may depend for their water entirely upon the precipitation (bogs and prairie potholes) or on the surface water from the rivers (riparian/floodplain wetlands), lakes (littoral zones), or the oceans (coastal wetlands). Wetlands also develop where the ground water is discharged naturally onto the surface (fens). Wetlands are usually grouped into freshwater and marine wetlands or into inland and coastal wetlands. The inland wetlands, occurring above the mean sea level, also include those developing in saline waters (salt lakes) besides those experiencing estuarine/brackish water conditions (lagoons and backwaters).
Hydrological Processes of Natural, Northern Forested Wetlands
Published in Carl C. Trettin, Martin F. Jurgensen, David F. Grigal, Margaret R. Gale, John K. Jeglum, Northern Forested Wetlands, 2018
In peatlands, bogs form primarily where precipitation exceeds evapotranspi-ration, the precipitation-derived water is poor in bases (Ca, Mg, etc.), and organic acid production yields high H+ levels buffered near pH 4. In some locations, usually near major watershed divides, where outwash sands (quartz) or bedrock (granite) are base-poor, bogs form in depressions fed by groundwater little different in chemical composition from ET-concentrated rain water. Fens represent a broad range of peatlands where the chemistry of the groundwater source has an increasingly higher concentration of bases (Ca, Mg, etc.) and a corresponding increase in the bicarbonate ion (HCO-3) that buffers water between pH 5.4 and 9. The groundwater source also varies in the strength of its total flow. Water table position relative to the peat surface rises as more groundwater enters a wetland, but the net impact on water table position is also controlled by the ease of water to leave the wetland at its outlet under the influence of wetland slope and physical constrictions. Similar outlet controls can be exhibited in bogs that are not elevated in raised domes above their surroundings. Mineral soil wetlands or mineral soil wetlands with thin organic surface layers exhibit similar ranges in water chemistry and water table position.
Water Resources
Published in Robert M. Sanford, Environmental Site Plans and Development Review, 2017
To some people, all wetland areas are merely “swamps.” However, there are all kinds of wetlands, including swamps. Knowing the type and nature of the wetland on a site helps in understanding the impacts of development plans. Wetland areas include bogs, marshes, swamps, vernal pools, mud flats, floodplains, and wet meadows. These different wetlands have their own soil and plant characteristics and distinct water conditions. Bogs contain organic soils, with sphagnum cover. The distinctive pitcher plant is found in bogs along with other plants indicative of still, shallow water. Like bogs, fens have peat and sphagnum moss, though less of it. Water flows through the fen, bringing nutrients to low sedges, mosses, and heath shrubs. Marshes have hydric soils and more than 50% coverage by herbaceous vegetation. Marshes can range from less than six inches of water during the growing season to about three feet. Shrub swamps have woody perennials covering more than half of the area. Wooded swamps are like a shrub swamp, but have trees that exceed 20 feet in height. A vernal pool is a temporary wetland appearing in the spring or fall and providing a vital reproductive habitat for small-sized wildlife species. Many of these species are amphibians or invertebrates that have ecological significance but may tend to be overlooked because they are not cute and furry. Mud flats occur along lakes and river outlets and inlets; their plants and soils may mirror other types of wetlands. Floodplain areas, beaver flowages, slough, potholes, and other areas that hold water can also be wetlands. The site plans should show the wetland, its associated features, and protective measures (Figure 5.5).
The Holocene of Sweden – a review
Published in GFF, 2022
Peat records from the HTM in Sweden are usually dominated by minerotrophic fen peat, which is less suitable for palaeoclimatic reconstructions than ombrotrophic peat (e.g., Barber & Charman 2003). One of few published records dominated by Sphagnum peat during the HTM, Kortlandamossen in Värmland, SW Sweden (Fig. 3), shows consistently high humification values between c. 7500 and 5000 cal a BP (Fig. 5), which is in line with warm and dry conditions and low local groundwater levels (Borgmark & Wastegård 2008). A peat record from Skåne, Viss Mosse (Fig. 4; Edvardsson et al. 2012), shows dry bog-surface conditions at 7300–6500 cal a BP.
Road salt chloride retention in wetland soils and effects on dissolved organic carbon export
Published in Chemistry and Ecology, 2020
Kayla M. McGuire, Kristin E. Judd
A number of factors may affect how salt affects DOC mobility in soils, and our findings that salt reduced or had no effect on DOC export is consistent with other studies in both uplands [34,36] and wetlands [43], although the underlying mechanism may differ or be difficult to discern. For example, Green et al. [39] found that while soils that had no previous exposure to road salts released more DOC upon salt application, soils with a long history of salt exposure released less DOC when exposed to salt than controls. Chronic salt exposure could enhance soil respiration through elevating the pH of naturally acidic soils (e.g. through enhanced NH4+ mobilisation [37]), or DOC mobilisation effects could be short-lived (i.e. the ‘when it’s gone, it’s gone’ hypothesis [39]). Previous chronic salt exposure could explain reduced DOC export from the urban PC soils that receive stream water overflow that can reach conductivities of >5 mScm−1 during snow melt (unpublished data). However, the other two sites used in our study are not likely to receive large salt inputs. Salt could also reduce DOC mobilisation by lowering pH, due to the mobile anion effect, reducing DOC mobilisation [38,39]. Such a mechanism was found in soils from a coastal fen peatland [41]. Our experimental setup also may have altered environmental conditions in a way that favoured that favoured DOC consumption over DOC mobilisation. A laboratory mesocosm experiment similar to ours found a reduction in DOC release under elevated Clin [67]. The frequent flushing events may have reduced anoxia in the wetland sediments and encouraged aerobic respiration. Interestingly, in our study, one site that did not experience a significant decrease in DOC export (PMP) had the lowest OM (Table 1), supporting the idea that shifts in microbial respiration may be the cause of reduced DOC export.