Landscape Ecology

, Volume 22, Issue 6, pp 911–924 | Cite as

Subsystems, flowpaths, and the spatial variability of nitrogen in a fluvial ecosystem

  • David Bruce LewisEmail author
  • Nancy B. Grimm
  • Tamara K. Harms
  • John D. Schade
Research Article


Nutrient dynamics in rivers affect biogeochemical fluxes from land to oceans and the atmosphere. Fluvial ecosystems are thus important environments for understanding spatial variability in nutrient concentrations. At the San Pedro River in semi-arid Arizona, USA, we investigated how variability in dissolved inorganic nitrogen (DIN) was regulated by subsystem type and hydrological flowpaths. The three subsystems we compared were the riparian zone, parafluvial (gravel bar) zone, and surface stream. DIN concentration was greater in the riparian zone than in the surface stream, suggesting that the riparian zone retains DIN and is a source of N for the surface stream. Parafluvial zones were too variable to generalize how they regulate DIN. Our hypothesis that subsystem type regulates DIN oxidation was too simple. The riparian and parafluvial zones host a mosaic of oxidizing and reducing conditions, as they exhibited highly variable ammonium to nitrate (NH 4 + :NO 3 ) ratios. Surface stream DIN was dominated by NO 3 . Along a subsurface flowpath in the riparian zone, we did not observe spatial covariation among the N forms and transformations involved in mineralization. We also compared spatial variability in solute concentrations between flowpaths and non-flowpath reference areas. Our mixed results suggest that spatial variability is regulated in part by flowpaths, but also by solute-specific processing length along a flowpath. To understand the distribution of N in fluvial ecosystems, subsystem type and flowpaths are readily discernable guides, but they should be coupled with other mechanistic factors such as biota and soil type.


Biogeochemistry Dissolved oxygen Ecosystem function Fluvial ecosystem Flux Heterogeneity Landscape Nitrogen Nutrient cycling Nutrient retention Southwest Stream 



We thank S Anderson of Gray Hawk Ranch, the U.S. Department of the Interior Bureau of Land Management, and the U.S. Department of Agriculture’s Agricultural Research Service for logistical support. We thank J Heffernan, A Huth, T Johns, C Kochert, J Koehler, C McLaughlin, J Petti, R Sheibley, J Smith, and R Sponseller for field and lab assistance. L Johnson and three anonymous reviews suggested many improvements to the manuscript. Funding came from the Science and Technology Center for Sustainability of semi-Arid Hydrology and Riparian Areas (NSF # OIA-9876800). DBL was supported by the Central Arizona-Phoenix Long-Term Ecological Research Project (NSF # DEB-9714833).


  1. Adair EC, Binkley D (2002) Co-limitation of first year fremont cottonwood seedlings by nitrogen and water. Wetlands 22:425–429CrossRefGoogle Scholar
  2. Baker MA, Valett HM, Dahm CN (2000) Organic carbon supply and metabolism in a shallow groundwater ecosystem. Ecology 81:3133–3148CrossRefGoogle Scholar
  3. Bernhardt ES, Likens GE, Buso DC, Driscoll CT (2003) In-stream uptake dampens effects of major forest disturbance on watershed nitrogen export. Proc Nat Acad Sci USA 100:10304–10308PubMedCrossRefGoogle Scholar
  4. Broadbent FE, Rauschkolb RS, Lewis KA (1980) Spatial variability of 15N and total nitrogen in some virgin and cultivated soils. Soil Sci Soc Am J 44:524–527CrossRefGoogle Scholar
  5. Burke IC, Lauenroth WK, Riggle R et al (1999) Spatial variability of soil properties in the shortgrass steppe: the relative importance of topography, grazing, microsite, and plant species in controlling spatial patterns. Ecosystems 2:422–438CrossRefGoogle Scholar
  6. Carpenter SR (2003) Regime shifts in lake ecosystems: pattern and variation. Oldendorf/Luhe, GermanyGoogle Scholar
  7. Dent CL, Grimm NB (1999) Spatial heterogeneity of stream water nutrient concentrations over successional time. Ecology 80:2283–2298CrossRefGoogle Scholar
  8. Evans RD, Ehleringer JR (1993) A break in the nitrogen cycle in aridlands? Evidence from the δ15N of soil. Oecologia 94:314–317CrossRefGoogle Scholar
  9. Fisher SG, Grimm NB, Martí E et al (1998) Material spiraling in stream corridors: a telescoping ecosystem model. Ecosystems 1:19–34CrossRefGoogle Scholar
  10. Fisher SG, Sponseller RA, Heffernan JB (2004) Horizons in stream biogeochemistry: flowpaths to progress. Ecology 85:2369–2379Google Scholar
  11. Gold AJ, Groffman PM, Addy K et al (2001) Landscape attributes as controls on ground water nitrate removal capacity of riparian zones. J Am Water Resour Assoc 37:1457–1464Google Scholar
  12. Grimm NB (1996) Surface-subsurface interactions in streams. In: Hauer FR, Lamberti GA (eds) Methods in stream ecology. Academic Press, San DiegoGoogle Scholar
  13. Grimm NB, Fisher SG (1984) Exchange between interstitial and surface water: implications for stream metabolism and nutrient cycling. Hydrobiologia 111:219–228CrossRefGoogle Scholar
  14. Grimm NB, Fisher SG (1986) Nitrogen limitation potential of Arizona streams and rivers. J Arizona-Nevada Acad Sci 21:31–43Google Scholar
  15. Grimm NB, Gergel SE, McDowell WH et al (2003) Merging aquatic and terrestrial perspectives of nutrient biogeochemistry. Oecologia 137:485–501PubMedCrossRefGoogle Scholar
  16. Grimm NB, Petrone KC (1997) Nitrogen fixation in a desert stream ecosystem. Biogeochemistry 37:33–61CrossRefGoogle Scholar
  17. Groffman PM, Bain DJ, Band LE et al (2003) Down by the riverside: urban riparian ecology. Frontiers Ecol Environ 1:315–321Google Scholar
  18. Groffman PM, Dorsey AM, Mayer PM (2005) N processing within geomorphic structures in urban streams. J North Am Benthol Soc 24:613–625Google Scholar
  19. Gross KL, Pregitzer KS, Burton AJ (1995) Spatial variation in nitrogen availability in three successional plant communities. J Ecol 83:357–367CrossRefGoogle Scholar
  20. Harms TK (2004) Impacts of plant community patchiness, vertical gradients, and temporal variability on microbial nitrogen transformations in a semi-arid riparian zone. Masters thesis, Arizona State University, Tempe, AZ, USAGoogle Scholar
  21. Hedin LO, Armesto JJ, Johnson AH (1995) Patterns of nutrient loss from unpolluted, old-growth temperate forests: evaluation of biogeochemical theory. Ecology 76:493–509CrossRefGoogle Scholar
  22. Hedin LO, von Fischer JC, Ostrom NE et al (1998) Thermodynamic constraints on nitrogen transformations and other biogeochemical processes at soil-stream interfaces. Ecology 79:684–703CrossRefGoogle Scholar
  23. Henry JC, Fisher SG (2003) Spatial segregation of periphyton communities in a desert stream: causes and consequences for N cycling. J North Am Benthol Soc 22:511–527CrossRefGoogle Scholar
  24. Hill AR (1996) Nitrate removal in stream riparian zones. J Environ Qual 25:743–755CrossRefGoogle Scholar
  25. Holmes RM, Fisher SG, Grimm NB (1994) Parafluvial nitrogen dynamics in a desert stream ecosystem. J North Am Benthol Soc 13:468–478CrossRefGoogle Scholar
  26. Jenerette GD, Wu JG, Grimm NB, Hope D (2006) Points, patches, and regions: scaling soil biogeochemical patterns in an urbanized arid ecosystem. Global Change Biol 12:1532–1544CrossRefGoogle Scholar
  27. Jones JB, Fisher SG, Grimm NB (1995) Nitrification in the hyporheic zone of a desert stream ecosystem. J North Am Benthl Soc 14:249–258CrossRefGoogle Scholar
  28. Lewis DB, Schade JD, Huth AK, Grimm NB (2006) The spatial structure of variability in a semi-arid, fluvial ecosystem. Ecosystems 9:386–397CrossRefGoogle Scholar
  29. McClain ME, Boyer EW, Dent CL et al (2003) Biogeochemical hot spots and hot moments at the interface of terrestrial and aquatic ecosystems. Ecosystems 6:301–312CrossRefGoogle Scholar
  30. Peterson BJ, Wollheim WM, Mulholland PJ et al (2001) Control of nitrogen export from watersheds by headwater streams. Science 292:86–90PubMedCrossRefGoogle Scholar
  31. Perakis SS, Hedin LO (2002) Nitrogen loss from unpolluted South American forests mainly via dissolved organic compounds. Nature 415:416–419PubMedCrossRefGoogle Scholar
  32. Pinay G, Clement JC, Naiman RJ (2002) Basic principles and ecological consequences of changing water regimes on nitrogen cycling in fluvial systems. Environ Manage 30:481–491PubMedCrossRefGoogle Scholar
  33. Pinay G, O’Keefe T, Edwards R, Naiman RJ (2003) Potential denitrification activity in the landscape of a western Alaska drainage basin. Ecosystems 6:336–343CrossRefGoogle Scholar
  34. Pringle CM (1990) Nutrient spatial heterogeneity: effects on community structure, physiognomy, and diversity of stream algae. Ecology 71:905–920CrossRefGoogle Scholar
  35. Schade JD, Fisher SG, Grimm NB, Seddon JA (2001) The influence of a riparian shrub on nitrogen cycling in a Sonoran Desert stream. Ecology 82:3363–3376CrossRefGoogle Scholar
  36. Schade JD, Martí E, Welter JR et al (2002) Sources of nitrogen to the riparian zone of a desert stream: implications for riparian vegetation and nitrogen retention. Ecosystems 5:68–79CrossRefGoogle Scholar
  37. Schade JD, Welter JR, Martí E, Grimm NB (2005) Hydrologic exchange and N uptake by riparian vegetation in an arid-land stream. J North Am Benthol Soc 24:19–28CrossRefGoogle Scholar
  38. Smith DF (1986) Small-scale spatial heterogeneity in dissolved nutrient concentrations. Limnol Oceanogr 31:167–171CrossRefGoogle Scholar
  39. Sponseller RA, Fisher SG (2006) Drainage size, stream intermittency, and ecosystem function in a Sonoran Desert landscape. Ecosystems 9:344–356CrossRefGoogle Scholar
  40. Stromberg JC (1993) Frémont cottonwood-Goodding willow riparian forests: a review of their ecology, threats, and recovery potential. J Arizona-Nevada Acad Sci 26:97–110Google Scholar
  41. Valett HM, Fisher SG, Grimm NB, Camill P (1994) Vertical hydrologic exchange and ecological stability of a desert stream ecosystem. Ecology 75:548–560CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • David Bruce Lewis
    • 1
    • 2
    • 4
    Email author
  • Nancy B. Grimm
    • 2
    • 1
  • Tamara K. Harms
    • 2
  • John D. Schade
    • 3
  1. 1.Global Institute of SustainabilityArizona State UniversityTempeUSA
  2. 2.School of Life SciencesArizona State UniversityTempeUSA
  3. 3.Biology DepartmentSt. Olaf CollegeNorthfieldUSA
  4. 4.Department of Crop and Soil SciencesThe Pennsylvania State UniversityUniversity ParkUSA

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