Is consolidation drainage an indirect mechanism for increased abundance of cattail in northern prairie wetlands?

Abstract

In the Prairie Pothole Region of North America, disturbances to wetlands that disrupt water-level fluctuations in response to wet–dry climatic conditions have the potential to alter natural vegetative communities in favor of species that proliferate in stable environments, such as cattail (Typha spp.). We evaluated the effect of water-level dynamics during a recent fluctuation in wet–dry conditions on cattail coverage within semipermanently and permanently ponded wetlands situated in watersheds with different land use and amounts of wetland drainage. We found that ponded water depth increase was significantly greater in wetlands where water levels were not near the spill point of the topographic basin, where banks were steeper, and in larger wetlands where past dry conditions had less influence on change in pond area. Proportion of the wetland covered by cattail was negatively correlated with increased water depth, bank slope and pond area. Our observations provide evidence that cattail coverage in prairie wetlands is regulated by water-level fluctuations and that land use surrounding the wetland might have an indirect effect on cattail coverage by altering water-level response to wet–dry climate conditions. For example, drainage of smaller wetlands into larger wetlands that are characterized by more permanent hydroperiods, leads to stabilized water levels near their spill point and is therefore a potential mechanism for increased cattail abundance in the northern prairie region.