Scale, Consumers and Lotic Ecosystem Rates (SCALER)

A key aim of SCALER is to allow extrapolation of typical experiments in streams to scales relevant to use or protection of the environment (i.e. human management).  Management agencies and research networks (e.g., the National Ecological Observatory Network) typically make measurements or monitor across networks.  Most networks assume that enough stations can be averaged to represent system properties.  With SCALER we ask How small-scale ecological experiments can be applied to understand operation of entire ecological systems?  Specifically we will ask how can we use cm- and reach-scale process measurements and consumer manipulation experiments to predict ecosystem characteristics of stream networks, and how do patterns of scaling compare across an array of North American biomes?  The experiment will be conducted in five biomes across the continent, each of which will have six sites with measurements nested at two scales (microhabitat, reach), and linked to watershed models.  Synoptic sampling will inform and test watershed scale patterns. Rates of metabolism and nutrient uptake and responses to consumer exclusions will be measured at micro (0.1 m) and reach (100 m) scales. Diversity and ecosystem function will be linked at a basic level by comparing metabolism and nutrient dynamics with and without consumers larger than 0.5 cm. Experimental results will be scaled with models: a) output of reach models based on decimeter-scale measurements will be compared to reach measurements, and b) output of watershed models based on reach measurements will be compared to carbon and nutrient patterns observed with synoptic sampling. Finally, the work will compare factors influencing scaling across widely divergent biomes associated with 5 LTER sites. A stoichiometric approach will be taken that considers interactions of source of carbon (from within or outside the system) and  nitrogen availability and transport, and how large consumers alter ecosystem stoichiometry. This approach is necessary because of strong upstream/downstream linkages and variations in the relative effects of biotic and abiotic factors at different positions within watersheds. Mechanistic explanation of how ecological measurements in streams can be scaled to watersheds will be provided, which is needed to understand both whole-system dynamics as well as to manage human impacts on entire watersheds. The experiments and modeling results will be relevant to ecology as a whole because few coupled nested experimental and theoretical scaling exercises have been undertaken in any environment. Coupling experiments and scaling exercises will characterize how plot-level experiments relate to patterns across larger scales such as landscapes (e.g., the stream network) and help understand the links between biodiversity and ecosystem function.