Changes in atmospheric circulation patterns affect midcontinent wetlands sensitive to climate

Twenty-seven years of data from midcontinent wetlands indicate that the response of these wetlands to extremes in precipitation- drought and deluge- persists beyond the extreme events. Chemical changes tran-scend such simple relations as increased salinity during dry periods because drought provides mechanisms for removal of salt by deflation and seepage to groundwater. Inundation of vegetation zones including rooted or floating mats of cattail (Typha glauca) can stimulate sulfate reduction and shift the anion balance from sulfate to bicarbonate dominance. Disruptions in the circulation of moisture-laden air masses over the midcontinent, as in the drought of 1988 and the deluge of 1993, have a major effect on these wetlands, which are representatives of the primary waterfowl breeding habitat of the continent. The glaciated prairie of North America encompasses an area of nearly 800,000 km2 (Luoma 1985) (Fig. 1) and contains lakes and wetlands that produce 50-80 % of the continent’s waterfowl (Batt et al. 1989). This prairie land-scape contains a mosaic of fresh and saline wetlands whose plant communities vary with salinity (Stewart and Kan