China
Africa
Explore chapters and articles related to this topic
Wetlands: Ecosystems
Published in Yeqiao Wang, Wetlands and Habitats, 2020
Wetlands perform key roles in the global hydrologic cycle. These transitional ecosystems vary considerably in their capacity to store and subsequently redistribute water to adjacent surface water systems, groundwater, the atmosphere, or some combination of these. Saturation in the root zone or water standing at or above the soil surface is key to defining a wetland. When oxygen levels in waterlogged soils decline below 1%, anaerobic (or reducing) conditions prevail. Most, but not all, wetland soils exhibit redoximorphic features formed by the reduction, translocation, and oxidation of iron (Fe) and manganese (Mn) compounds; the three basic kinds of redoximorphic features include redox concentrations, redox depletions, and reduced matrix.[1] Microbial transformations in flooded soils also impact other biogeochemical cycles (C, N, P, S) at various spatial and temporal scales. Several of the most rapidly disappearing wetland ecosystems in North America are profiled here, in terms of properties and processes.
Nitrate pollution and expansion of free-floating plants in 3 lower Wisconsin River oxbow lakes
Published in Lake and Reservoir Management, 2023
David W. Marshall, Kenneth Wade, Jean L. Unmuth
An environmental contractor operated a geoprobe track mounted drill to install thirty-four 5.1 cm water table wells and piezometers across the sand terrace, with depths ranging from 2.3 to 24.9 m below ground surface. All terrace well nests were installed in nonagricultural areas. Most of the wells were constructed in clusters of 3 or 4, with screen lengths varying from 3 m for water table wells to 0.6 m for piezometers. Drill core soil samples at each well cluster location confirmed the presence of medium well sorted sand, including some fine sand, coarse sand, and gravel, consistent with previous Pleistocene terrace drill core analysis (Pfeiffer et al. 2006). Clay and organic material were scarce and we found no evidence of redoximorphic conditions such as staining, odor, or mottling in the core samples. Five additional wells were manually driven into the floodplain. Two of the floodplain wells were downgradient of Norton Slough. The floodplain deposits contained sand but also finer organic soils that exhibited redoximorphic features including mottling and iron depletion. Pfeiffer et al. (2006) identified LWSR floodplain reducing conditions that had contributed to nitrate attenuation.