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Abstract
Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.
Citation
Bernot, Melody J.; Sobota, Daniel J.; Hall, Robert O.; Mulholland, Patrick J.; Dodds, Walter K.; Webster, Jackson R.; Tank, Jennifer L.; Ashkenas, Linda R.; Cooper, Lee W.; Dahm, Clifford N.; Gregory, Stanley V.; Grimm, Nancy B.; Hamilton, Stephen K.; Johnson, Sherri L.; McDowell, William H.; Meyer, Judith L.; Peterson, Bruce; Poole, Geoffrey C.; Valett, H. Maurice; Arango, Clay; Beaulieu, Jake J.; Burgin, Amy J.; Crenshaw, Chelsea; Helton, Ashley M.; Johnson, Laura; Merriam, Jeff; Niederlehner, B.R.; O'Brien, Jonathan M.; Potter, Jody D.; Sheibley, Richard W.; Thomas, Suzanne M.; Wilson, Kym. 2010. Inter-regional comparison of land-use effects on stream metabolism. Freshwater Biology. 55: 1874-1890.