Life on the Edge: The Ecology of Great Plains Prairie Streams

P streams and rivers historically formed a critical part of Great Plains ecosystems. However, such streams have received less attention from ecologists than streams in forested regions (Matthews 1988). Prairie streams not only are vital habitats that control downstream water quality but also can serve as model systems for studying disturbance ecology and related issues of resistance and resilience in temperate fresh waters. Biological responses to disturbance are particularly easy to document, because prairie stream organisms have exaggerated life-history characteristics that are well suited to survival in such habitats (Lytle 2002). Understanding the ecology of Great Plains streams is imperative, because they represent a component of the everdwindling North American supply of unpolluted surface freshwater resources and are home to a number of threatened or endangered species, including the Topeka shiner (Notropis topeka), the Neosho madtom (Noturus placidus), and many freshwater mussels in the United States. North American prairie once covered 160 million hectares, but it is now one of the most endangered biomes on the continent (Samson and Knopf 1994). For instance, about 95% of the once-extensive tallgrass prairie has been lost (Samson and Knopf 1994). Streams in prairies are even more endangered, because many of the remaining fragments of prairie are not large enough to encompass a significant, functional watershed. Most areas of the Great Plains that were formerly prairie are now heavily affected by agriculture or urbanization, resulting in pollution, hydrologic disturbance, and physical modification (e.g., channelization and alteration of riparian vegetation) of streams. In addition to the aboveground insults, vast areas of the Ogallala–High Plains aquifer and other large aquifers under grasslands have been overexploited, literally sucking dry many streams of the Great Plains. Understanding the ecosystem function of small streams in the Great Plains region is essential, because those streams represent a key interface between terrestrial habitats and downstream areas, and substantial in-stream nutrient processing may control downstream water quality (Peterson et al. 2001). Thus, physical and biological factors that influence the ecosystem function of native prairie streams, including even small headwater reaches, must be studied to help assess current water quality issues on both local and continental scales. Knowledge of community and ecosystem dynamics will help in designing such studies, and these dynamics are driven in large part by the variable hydrology that results from the climate of the Great Plains. Hydrology is one of the most fundamental components of the physical template of all streams, and flooding and drying