Prairie Pothole Wetlands – Suggestions for Practical and Objective Definitions and Terminology

Abstract

Prairie pothole wetlands are subject to large year-to-year and decadal variability of precipitation, resulting in large variations in ponded area, plant communities and ecological functionality that obscure trends in wetland conditions caused by changes in climate and land use. Descriptions and analyses of these variations and trends require practical and objective definitions of pothole wetlands that can be used to establish the boundaries of individual wetlands, detect long-term changes of these boundaries, and distinguish wetlands from lakes and from small non-wetland depressions. The boundaries of prairie pothole wetlands should ideally be defined on the basis of wetland soils, which are more stable and persistent than vegetation and ponded water. The latter are necessarily used as indicators of wetland conditions through time because they are amenable to remote sensing and regional wetland inventories. However, the relationships between wetland ponds, vegetation and soil zones need improved documentation. Wetlands are persistent and stable landscape features (unless they are drained or filled). Some ecological functions of wetlands such as waterbird habitat may be seasonal, but other important hydrological and biochemical functions act year-round whether or not a pond is present. Phrases such as “seasonal wetland” that refer to the duration of ponded water should be avoided and terms such as “wetland”, “depression” and “pond” should be used with clear definitions that are accepted across the wetland disciplines. Commonly used wetland classifications based on vegetation zones and duration and salinity of ponds should incorporate reference to the decadal-scale time period for which the descriptions apply.