| Abstrakt: |
This paper documents and characterizes a rare form of boreal wetlandassociated with the nests of whooping cranes, an endangered species.Diatom ponds are found in wetlands in association with bulrush marshes. They are shallow (<50 cm deep) and vary in size from 10 to >1000 m in diameter, may evaporate down to diatom muck by late summer, are strongly influenced by dissolution of gypsum, and are circumneutral to alkaline and high in sulphates. Aquatic macrophytes are few. Pond waters are clear, and the predominant primary producers are a benthic diatom community that gives the ponds a characteristic yellow color (viewed from the air). As the diatom ponds dry, they change color fromyellow to pink (when water table is at the surface) to cream (due toa dried diatom and sulphate crust). Diatomaceous earth or sedimentary peat underlies the ponds, which exist in a dynamic relationship with bulrush marshes, wet meadows, fens, and bogs. In the U.S. wetland classification system, diatom ponds fit most nearly within the palustrine, unconsolidated bottom, aquatic bed type. In the Canadian wetlandclassification system, the diatom ponds might fit in the marsh/shallow open water complex, with a new distinction at the type level. The association between nesting cranes and diatom ponds may be due to a combination of factors such as long sight lines for detection of predators, the proximity of bulrush (their favored nesting material), and use of the ponds for feeding. [ABSTRACT FROM AUTHOR] |
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