Landscape Ecology

, Volume 20, Issue 7, pp 791–798 | Cite as

Evaluating the Relative Roles of Ecological Regions and Land-cover Composition for Guiding Establishment of Nutrient Criteria

  • James D. Wickham
  • Kurt H. Riitters
  • Timothy G. Wade
  • K. Bruce Jones
Research Article


The continuing degradation of United States surface waters by excessive nutrient loads has motivated the establishment of nutrient criteria for streams, lakes, and estuaries as a means to protect aquatic resources. Nutrient criteria have been established based on ecoregional differences, recognizing that geographic variation in climate, topography, geology, and land use require use of different criteria values for different regions of the continental United States. Several studies have demonstrated that land-cover composition also strongly influences nutrient concentrations and yields. We examined the relative importance of ecoregions and watershed land-cover composition in explaining variability in nitrogen (N) and phosphorus (P) concentrations by re-analyzing the National Eutrophication Survey (NES) data reported by Omernik (1977). The variance of N concentrations among land-cover composition classes within ecoregions was six times larger than the variance among ecoregions. For P concentrations, land-cover composition within ecoregions accounted for three times more variance than ecoregions themselves. Variance across ecoregions was only weakly significant after accounting for variance in land-cover composition within ecoregions. The results suggest that the relationship between land-cover composition and nutrient concentrations in aquatic systems should also be used to help guide establishment of nutrient criteria.


Clean Water Act (CWA) Eutrophication Nitrogen Phosphorus Scale Variance component analysis 


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Copyright information

© Springer 2005

Authors and Affiliations

  • James D. Wickham
    • 1
  • Kurt H. Riitters
    • 2
  • Timothy G. Wade
    • 1
  • K. Bruce Jones
    • 3
  1. 1.National Exposure Research Laboratory (NERL)U.S. Environmental Protection Agency (E243-05)USA
  2. 2.Southern Research StationU.S. Forest ServiceUSA
  3. 3.National Exposure Research Laboratory (NERL)U.S. Environmental Protection AgencyLas VegasUSA

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