Collaborative Research: Hierarchical Functioning of River Macrosystems in Temperate Steppes From Continental to Hydrogeomorphic Patch Scales

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The need to understand and manage ecosystems at larger regional to continental scale macrosystem levels is becoming increasingly crucial with global climate changes and impacts of exotic plants and animals in freshwater rivers and lakes. Macrosystem management requires an understanding of how different levels of spatial complexity (within a stream reach to entire river valley scales) and biotic organization (populations to ecosystems) affect the functioning of rivers and lakes. The present study will provide this information for 18 rivers spread equally between the two largest temperate steppe biomes of the world: the North American Great Plains and the Euro-Asian Steppes (including those in Mongolia). This project will provide research experiences for under-represented participants (particularly rural and Native American students), stimulate STEM program recruitment in largely under-represented (EPSCoR) states, support some faculty and students at primarily undergraduate institutions, and contribute to scientific education at both graduate and undergraduate institutions in two countries.These rivers flow through 3 major types of ecoregions within these temperate steppe biomes: mountain steppe shrublands, short-to-tall grasslands, and semi-arid shrublands. Scientists and students from the USA and Mongolia will sample the structure and functioning of these 18 rivers in a variety of hydrogeomorphic areas, such as constricted, meandering, braided, and anastomosing channel sections. Despite their similarity in biome and ecoregional types, the river macrosystems of the Great Plains and the Mongolian steppes vary substantially in fauna, flora, and community through ecosystem functioning. These variations result from differences in climatic patterns, the degree of riverine landscape modification (e.g., by dams, levees, and riparian modification), and the naturalness of the resident fauna. For example, most rivers in the USA contain some dams and many exotic fauna have been introduced, while the vast majority of Mongolian rivers contain no dams and their aquatic fauna is almost exclusively natural and different from those in the USA. Moreover, the Central Asian subcontinental area of Mongolia has one of the strongest warming signals on earth, with air temperatures rising three times faster than the overall northern hemisphere average. Consequently, riverine macrosystems in the USA can help predict changes to Mongolian rivers as a result of pending dam construction and possible species introductions to some rivers, while knowledge of responses of Mongolian macrosystems to more rapid climatic changes can help predict future effects in U.S. rivers. Therefore, this project's goals are to: (a) compare and contrast hierarchical scaling relationships and effects of system drivers and cross-scale interactions on rivers in similar biomes and ecoregions of the two continents; and (b) evaluate effects of climatic changes and anthropogenic disturbance to these river macrosystems.