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

Jason C. Neff, Alan R. Townsend, Gerd Gleixner, Scott J. Lehman, Jocelyn Turnbull, William D. Bowman

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Soils contain the largest near-surface reservoir of terrestrial carbon1 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 documented2, 3, 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, mineralassociated 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.

    Original languageEnglish
    Pages (from-to)915-917
    Number of pages3
    JournalNature
    Volume419
    Issue number6910
    DOIs
    StatePublished - Oct 31 2002

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