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This article in SSSAJ

  1. Vol. 67 No. 4, p. 1206-1212
     
    Received: Sept 10, 2001
    Published: July, 2003


    * Corresponding author(s): ttcf@vt.edu
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doi:10.2136/sssaj2003.1206

Sources of Uncertainty Affecting Soil Organic Carbon Estimates in Northern New York

  1. John M. Galbraith *a,
  2. Peter J. A. Kleinmanb and
  3. Ray B. Bryantb
  1. a Crop & Soil Environmental Sciences Dep., Virginia Polytechnic Institute and State Univ., 239 Smyth Hall (0404), Blacksburg, VA 24061
    b USDA-ARS, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA 16802-3702

Abstract

Estimations of regional soil organic C (SOC) stores are sensitive to map scale effects, the geography of soil resources, and uncertainty stemming from SOC values assigned to soil series. This study assessed uncertainty associated with regional SOC estimation for the Tughill Plateau (Major Land Resource Area [MLRA 141]) of northern New York. Soil samples from 103 sites, representing 30 soil series mapped within the Tughill Plateau, were collected from the upper meter and analyzed to develop a series-specific SOC database. Four 24 km2 subregions of the Plateau were identified and soil survey maps of four different scales ranging from 1:15840 to 1:750000 were compared. Soil survey maps were digitized, and their respective map unit compositions and areas were related to the series-specific SOC database to calculate SOC (weighted by land extent). Estimates using different survey map scales ranged from 16.6 to 17.6 kg C m−2 Smaller-scale soil survey maps (1:250000 and 1:750000) produced SOC estimates that were greater significantly than the 16.7 kg C m−2 estimated using the large-scale reference survey maps (1:15840). Differences were caused by the process of map generalization, as soil series with lower mean SOC that occurred on the 1:15840 survey maps were replaced by series that had higher SOC on the 1:250000 and 1:750000 survey maps. Although significantly different, area-weighted mean SOC estimates varied by <5%. The greatest uncertainty in regional SOC estimation originated from the variation in SOC values assigned to soil series, with coefficients of variation (CV) ranging from 3 to 87%.

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Copyright © 2003. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.67:1206–1212.