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This article in SSSAJ

  1. Vol. 67 No. 2, p. 527-539
     
    Received: May 6, 2002
    Published: Mar, 2003


    * Corresponding author(s): venterea@soils.umn.edu
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doi:10.2136/sssaj2003.5270

Landscape Patterns of Net Nitrification in a Northern Hardwood-Conifer Forest

  1. Rodney T. Venterea *a,
  2. Gary M. Lovetta,
  3. Peter M. Groffmana and
  4. Paul A. Schwarzb
  1. a Institute of Ecosystem Studies, P.O. Box AB, Millbrook, NY 12545
    b Dep. of Forest Science, Oregon State Univ., Corvallis, OR, 97331

Abstract

The production of NO 3 in forest soils is an important process influencing the form of N available for plant uptake and the potential for off-site N losses. We sampled mineral and organic soil horizons in 100 plots distributed across a 3160-ha hardwood-conifer forest in central New Hampshire to examine patterns of net nitrification rate (NR) and NO 3 concentration associated with physiographic features and vegetation abundances. Net NR and NO 3 concentrations each varied by a factor of 150 across the forest. Greater rates of net NO 3 production were associated with higher plot elevation, extent of southerly aspect, greater abundance of sugar maple (Acer saccharum Marsh.) and striped maple (Acer pensylvanicum L.), and lower abundances of coniferous trees. Regression models incorporating these factors accounted for 52% of the variance in NR across the entire valley. Higher soil water contents, N mineralization rates, and total N concentrations in higher elevation plots and higher N mineralization and respiration rates in more south-facing plots contributed to the landscape patterns. Incorporation of measured soil C/N ratios together with landscape factors accounted for an additional 10% of the variation. Regression models incorporating vegetation, physiographic, and soils data explained 62 to 73% of the variance in soil C/N ratios across the valley. Our results demonstrate how multiple biotic and abiotic factors combine to generate wide variation in NO 3 production, and provide a quantitative basis for estimating how vegetation shifts and climate change may influence N cycling in heterogeneous landscapes characteristic of many temperate forest ecosystems.

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Copyright © 2003. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.67:527–539.