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      Variable effects of nitrogen additions on the stability and turnover of soil carbon.

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          Abstract

          Soils contain the largest near-surface reservoir of terrestrial carbon and so knowledge of the factors controlling soil carbon storage and turnover is essential for understanding the changing global carbon cycle. The influence of climate on decomposition of soil carbon has been well documented, but there remains considerable uncertainty in the potential response of soil carbon dynamics to the rapid global increase in reactive nitrogen (coming largely from agricultural fertilizers and fossil fuel combustion). Here, using 14C, 13C and compound-specific analyses of soil carbon from long-term nitrogen fertilization plots, we show that nitrogen additions significantly accelerate decomposition of light soil carbon fractions (with decadal turnover times) while further stabilizing soil carbon compounds in heavier, mineral-associated fractions (with multidecadal to century lifetimes). Despite these changes in the dynamics of different soil pools, we observed no significant changes in bulk soil carbon, highlighting a limitation inherent to the still widely used single-pool approach to investigating soil carbon responses to changing environmental conditions. It remains to be seen if the effects observed here-caused by relatively high, short-term fertilizer additions-are similar to those arising from lower, long-term additions of nitrogen to natural ecosystems from atmospheric deposition, but our results suggest nonetheless that current models of terrestrial carbon cycling do not contain the mechanisms needed to capture the complex relationship between nitrogen availability and soil carbon storage.

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          Author and article information

          Journal
          Nature
          Nature
          Springer Science and Business Media LLC
          0028-0836
          0028-0836
          Oct 31 2002
          : 419
          : 6910
          Affiliations
          [1 ] Earth Surface Processes Team, Geologic Division, US Geological Survey, MS 980, Denver Federal Center, Denver, Colorado 80225, USA. jneff@usgs.gov
          Article
          nature01136
          10.1038/nature01136
          12410307
          fb9724b7-d709-4728-82b4-a51c2d19ece8
          History

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