Hydrology, Water Chemistry and Ecological Relations in the Raised Mound of Cowles Bog

Abstract

1) The Cowles Bog National Natural Landmark and the wetlands between the dunes near the south shore of Lake Michigan, in Indiana, contain plant species that are typical of circum-neutral fens.(2) The distribution of eight, rather sharply delineated, vegetation types correlates most strongly with water level variations resulting from the presence of a 4.1-ha convex peat mound.(3) A network of shallow ground-water wells installed in the wetland has identified an upwelling of water under artesian pressure at sites underlying the mound.(4) The well-buffered water, containing high concentrations of inorganic solutes, is derived from an aquifer that is recharged on an upland moraine and is confined beneath a clay till sheet.(5) A breach in this clay layer beneath the mound allows water to flow upward and radially outward as the hydraulic head is dissipated in the overlying marl and peat.(6) The marl and organic lake sediments in the wetland were formed during the Nipissing level of ancestral Lake Michigan (4000-6000 years ago) when the wetland basin was probably a small bay of the lake.(7) The peat mound developed when the lake level fell from the Algoma through to modern times. This increased the difference in hydraulic head and increased spring flows, which in turn induced peat formation. $ Present address: P.O. Box 158 B, Mancos, Colorado 81321, U.S.A.

Nonlinear dynamics in ecosystem response to climatic change: Case studies and policy implications

“…Over longer time periods ranging from decades to centuries to millennia, the expected linear response is also deeper open water with few emergent species during cool, wet climate phases, and shallow marsh with shoreline and mudflat species during warm, dry phases (Singer et al, 1996). Prolonged warm, dry phases with greater primary production by emergent species may accelerate basin infilling in protected areas not subject to wave attack (Wilcox et al, 1986;Wilcox and Simonin, 1987). Successional processes may accompany shallowing of the basins, leading to further vegetation changes that include the invasion of shrubs and trees (Walker, 1970;Keddy, 2000), although return of high water can reset the successional stage again (van der Valk, 1981;Jackson et al, 1988;Hannon and Gaillard, 1997).…”

“…This artesian flow likely results from a discontinuity in an underlying clay till sheet that allows flow from a confined aquifer to reach the surface. These hydrologic conditions are conducive to growth of northern white cedars (Voss, 1972;Swink and Wilhelm, 1979;Wilcox et al, 1986) and explain the prominence of cedar swamp in nearby wetlands 45, 49, 63, and 64, as well as a noticeable presence of cedars in lakeward wetlands that receive this flow of water in a pass-through fashion from wetland to wetland. The modern vegetation and the paleoecological record of vegetation changes suggest that this continuous source of cold water provides the predominant control on plant communities.…”

Regional and local hydrogeology of calcareous fens in the Minnesota River basin, USA

“…One such fen in southern Wisconsin has a slope of about 5% (Kratz et al 1981), and Cowles Bog (actually a mounded fen) in northern Indiana has a slope of about 3-4% as inferred from a contour map of the site (Wilcox et at. 1986).…”

Hydrological behaviour of a drained agricultural peat catchment in the tropics. 1: Rainfall, runoff and water table relationships

“…Watanabe et al (2009) and Sillins and Rothwell (1998) found that draining of a naturally shallow water table expedites the oxidation process of the peat materials and thus inevitably results in land subsidence. Wilcox et al (1986) and Worrall et al (2007) reported that draining of naturally acidic peat water increases the acidity level of the peat water due to the increase of humification. This causes severe damage to the habitats of flora and fauna and the mangrove system.…”