Metamorphosis in river ecology: from reaches to macrosystems

摘要

1. A metamorphic shift in the focus of aquatic ecological research is needed to (i) better understand the functioning of river ecosystems at large spatiotemporal scales; (ii) respond to threats from climate change, species invasions and increased pressure for more river dams and interbasin water transfer; and (iii) meet critical needs for catchment-level management. 2. Implementing changes in research and management necessitate new spatiotemporal and research domains and a partial shift from reach-level studies to macrosystem ecology. 3. Macroecology, as defined here, and associated processes usually cannot be understood simply by scaling up information from smaller extent and finer grain samples because of problems of connectivity and spatial heterogeneity of crucial system components and entanglements from cross-scale interactions producing threshold responses and other nonlinear dynamics. 4. An important driver of macrosystem research in terrestrial and aquatic ecosystems is the immediate and long-term danger from global climate change, which will alter flow regimes, water temperatures and dissolved oxygen in riverine landscapes. 5. An initial step in implementing metamorphic change in river science is to integrate the newest macroecological perspectives with current large-scale riverine concepts, especially ones emphasising the importance of tributary patterns and junctions (Network Dynamics Hypothesis) or the hydrogeomorphic patch nature of rivers at multiple scales (Riverine Ecosystem synthesis). 6. The hierarchical nature, system boundaries and research domains of riverine macrosystem ecology are examined, and twelve sample research questions are provided to help direct future research. 7. Current research impediments to riverine macroecology are discussed, and a partial solution based on the need for Long-Term Ecological Research-like sites (each with a central organisational hub and a diffuse, multi-institutional network of data collection stations at strategic catchment points) is proposed.