Relationship of landscape position and groundwater input in Northern Wisconsin kettle-hole peatlands
The amount of groundwater a peatland receives is an important determinant of the peatland’s interstitial water chemistry. Most, if not all, northern Wisconsin peatlands receive some groundwater input, but it is unclear (1) how much groundwater enters any particular peatland and (2) to what degree the magnitude of groundwater input is a function of very local (scale of m2 to ha) versus regional (scale of km2 ) landscapes. We investigated these questions in nine northern Wisconsin kettle-hole bogs located along a defined groundwater flow system. Using silica as a groundwater tracer, we used a mass balance approach to estimate groundwater input to each peatland. If regional flow paths are important, then more groundwater should enter peatlands low in the flow system and iess groundwater should enter peatlands high in the groundwater flow system. Our results suggest that groundwater input is controlled by a mixture of regional and local landscape effects. In general, peatlands low in the flow system exhibited higher concentrations of silica and appeared to have larger amounts of groundwater input than peatlands higher in the flow system. However, superimposed on this regional pattern are local effects. For example, peatlands adjacent to major lakes had silica concentrations similar to that of the adjoining lake, and a peatland bordered by a high mineral ridge had more groundwater input than predicted from regional flow systems alone.