Vegetation and Hydrology Differences among Four Previously Farmed Fens

A fen is a type of wetland that is supported by groundwater, contains the water in the root zone but it is not usually inundated, and can accumulate organic and/or carbonate substrates. Fens represent a biologically diverse ecosystem in the Midwestern temperate zone. However, they are endangered systems in Wisconsin. A study of five fens was made to understand why vegetation differs among them. Four of these fens were agricultural lands from 1968 to 1998, the other was never farmed. Fen native plants have their roots saturated during the year. If the fen is invaded by non native plants, it is possible that the depth of the water table is not adequate to support those fen natives. Vegetation sampling, using a 1m² quadrant, was made to classify the vegetation associated with each fen. We also measured hydrology, using wells and piezometers, in each fen throughout the summer to account for groundwater levels. Our analysis was made trough PC-ORD to determine the species that account for more difference and how important the depth of the water table was among the plants. Preliminary results show that the depth of the water table is an important factor for the native plants to recolonize the farmed fens, but it is not the only one.