Schaefer,S.C. and Alber.M.(2007): Temporal and spatial trends in nitrogen and phosphorus inputs to the watershed of the Altamaha River, Georgia, USA. Biogeochemistry, 86, 231-249.

『米国ジョージア州アルタマハ川の流域への窒素とリン投入の時空間的傾向』


Abstract
 The watershed of the Altamaha River, Georgia, is one of the largest in the southeastern U.S., draining 36,718 km2 (including parts of metro Atlanta). We calculated both nitrogen (fertilizer, net food and feed import, atmospheric deposition, and biological N fixation in agricultural and forest lands) and phosphorous (fertilizer and net food and feed import) inputs to the watershed for 6 time points between 1954 and 2002. Total nitrogen input rose from 1,952 kg N km-2 yr-1 in 1954 to a peak of 3,593kg N km-2 yr-1 in 1982 and then declined to 2,582kg N km-2 yr-1 by 2002. Phosphorus inputs rose from 409 kg P km-2 yr-1 in 1954 to 532 kg P km-2 yr-1 in 1974 before declining to 412 kg P km-2 yr-1 in 2002. Fertilizer tended to be the most important input of both N and P to the watershed, although net food and feed import increased in importance over time and e\was the dominant source of N input by 2002. When considered on an individual basis, fertilizer input tended to be highest in the middle portions of the watershed (Little and Lower Ocmulgee and Lower Oconee sub-watersheds) whereas net food and feed imports were highest in the upper reaches (Upper Oconee and Upper Ocmulgee sub-watersheds). Although the overall trend in recent years has been towards decreases in both N and P inputs, these trends may be offset due to continuing increase in animal and human populations.

Keywords: Altamaha River; Nitrogen budgets; Nutrient inputs; Phosphorus budgets; spatial distribution; Temporal trends』

Introduction
Methods
 Watershed delineation
 Nutrient budgets
  Fertilizer
  Net food and feed import
  Net atmospheric N deposition
  Nitrogen fixation
  Non-food crop export
Results
 Temporal trends
  Fertilizer
  Net food and feed import
  Net atmospheric N deposition
  Biological N fixation
  Non-food crop export
  Dominant sources
 Spatial distribution
  Fertilizer
  Food and feed import
  Net atmospheric N deposition
  Biological N fixation
  Overall nutrient distribution
Discussion
Acknowledgments
References


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