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Long-term warming restructures Arctic tundra without changing net soil carbon storage


High latitudes contain nearly half of global soil carbon, prompting interest in understanding how the Arctic terrestrial carbon balance will respond to rising temperatures1,2. Low temperatures suppress the activity of soil biota, retarding decomposition and nitrogen release, which limits plant and microbial growth3. Warming initially accelerates decomposition4,5,6, increasing nitrogen availability, productivity and woody-plant dominance3,7. However, these responses may be transitory, because coupled abiotic–biotic feedback loops that alter soil-temperature dynamics and change the structure and activity of soil communities, can develop8,9. Here we report the results of a two-decade summer warming experiment in an Alaskan tundra ecosystem. Warming increased plant biomass and woody dominance, indirectly increased winter soil temperature, homogenized the soil trophic structure across horizons and suppressed surface-soil-decomposer activity, but did not change total soil carbon or nitrogen stocks, thereby increasing net ecosystem carbon storage. Notably, the strongest effects were in the mineral horizon, where warming increased decomposer activity and carbon stock: a ‘biotic awakening’ at depth.

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Figure 1: A canonical discriminant analysis plot reveals the loss of trophic heterogeneity across soil horizons in the greenhouse treatment relative to control conditions.
Figure 2: A discontinuous record of the difference between greenhouse treatment and control soil.


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This research was supported by a DOE Global Change Education Program Graduate Fellowship, a Leal Anne Kerry Mertes scholarship, and Explorer’s Club grant to S.A.S., NSF OPP-1023524 to J.P.S., NSF OPP-0425606 and NSF OPP-0909441 to J.C.M., NSF OPP-0425827 and NSF OPP-0909507 to L.G., and the Arctic LTER program NSF-DEB 1026843 to G.R.S. We thank J. Laundre for temperature and thaw depth data. We also thank three anonymous reviewers, C. D’Antonio, J. King, and S. Viswanathan for comments that greatly improved this manuscript.

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S.A.S., J.C.M., L.G., J.P.S. and G.R.S. conceived the study and designed scientific objectives. J.C.M. and R.T.S. collected the soil food web data, L.G. and G.R.S. collected the plant data, S.A.S. and J.P.S. collected the soil chemistry data. S.A.S., J.C.M., L.G. and R.T.S. carried out statistical analyses. S.A.S. wrote the paper. J.P.S., J.C.M., L.G. and G.R.S. provided textual edits and all authors commented on the analysis and presentation of the data.

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Correspondence to Seeta A. Sistla.

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Sistla, S., Moore, J., Simpson, R. et al. Long-term warming restructures Arctic tundra without changing net soil carbon storage. Nature 497, 615–618 (2013).

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