REGIONAL LINKAGES BETWEEN RAISED BOGS AND THE CLIMATE, GROUNDWATER, AND LANDSCAPE OF NORTH-WESTERN MINNESOTA

1 Landsat imagery was used to map the distribution of 127 raised bogs in northwestern Minnesota. Bogs collectively cover 1236 km(2) (16% of the study area) despite the relatively dry regional climate and period ic droughts. 2 The physical, chemical, and biotic properties of these bogs have no apparent relationship to the westward climatic gradient i ndicating a high degree of buffering from changes in moisture stress. 3 Most bogs are located where groundwater discharge moderates moisture losses to the atmosphere and may decouple bogs from a direct climatic control. Bogs are also consistently related to physiographic features , such as drainage divides, interfluves of tributary streams, and beac h ridges that constrain the surface and groundwater hydrology. 4 Durin g droughts groundwater moves upward through the peat column toward the depressed water table, which is located 1-2 m below the peat surface. During moist periods, however, water-table mounds within these bogs d rive surface water downward deflecting the deeper upwardly moving grou ndwater laterally to the bog margins. 5 Such short-term reversals in f low have little effect on the pore-water chemistry of major cations, w hich reflect the predominant downward flow over the past decade. Sever al chemical species, however, behave nonconservatively and respond mor e directly to climatic change. 6 Discharge zones for groundwater seem to be an essential prerequisite for bog formation in arid regions. Fea t accumulation should be most rapid over discharge zones, which can ma intain water table mounds, even during droughts Once a peat mound has formed, its higher water table will drive local recharge cells, which isolate the vegetation from groundwater and facilitate the development of a raised bog.